dh_assistant

#!/usr/bin/perl

=head1 NAME

dh_assistant - tool for supporting debhelper tools and provide introspection

=cut

use strict;
use warnings;
use constant EXIT_CODE_LINT_ISSUES_FOUND => 2;
use Debian::Debhelper::Dh_Lib;
use JSON::PP ();

=head1 SYNOPSIS

B<dh_assistant> B<I<command>> [S<I<additional options>>]

=head1 DESCRIPTION

B<dh_assistant> is a debhelper program that provides introspection into the
debhelper stack to assist third-party tools (e.g. linters) or third-party
debhelper implementations not using the debhelper script API (e.g., because
they are not written in Perl).

=head1 COMMANDS

The B<dh_assistant> supports the following commands:

=head2 active-compat-level (AJSON)

B<Synopsis>: B<dh_assistant> B<active-compat-level>

Outputs information about which compat level the package is using.

For packages without valid debhelper compatibility information (whether missing, ambiguous,
not supported or simply invalid), this command operates on a "best effort" basis and may abort
when error instead of providing data.

The returned JSON dictionary contains the following key-value pairs:

=over 4

=item active-compat-level

The compat level that debhelper will be using.  This is the same as B<DH_COMPAT> when present
or else B<declared-compat-level>.  This can be B<null> when no compat level can be detected.

=item declared-compat-level

The compat level that the package declared as its default compat level.  This can be B<null>
if the package does not declare any compat level at all.

=item declared-compat-level-source

Defines how the compat level was declared.  This is null (for the same reason as
B<declared-compat-level>) or one of:

=over 4

=item debian/compat

The compatibility level was declared in the first line F<debian/compat> file.

=item X-DH-Compat: <C>

The compatibility was declared in the F<debian/control> via a the B<X-DH-Compat>
field. In the output, the B<C> is replaced by the actual compatibility level.
A full example value would be:

   X-DH-Compat: 15

=item Build-Depends: debhelper-compat (= <C>)

The compatibility was declared in the F<debian/control> via a build dependency on the
B<< debhelper-compat (= <C>) >> package in the B<Build-Depends> field.  In the output,
the B<C> is replaced by the actual compatibility level.  A full example value would be:

   Build-Depends: debhelper-compat (= 15)

=back

=back

=head2 supported-compat-levels (AJSON, CRFA)

B<Synopsis>: B<dh_assistant> B<supported-compat-levels>

Outputs information about which compat levels, this build of debhelper knows
about.

This command accepts no options or arguments.

=head2 which-build-system (AJSON)

B<Synopsis>: B<dh_assistant> B<which-build-system> [S<I<build step>>] [S<I<build system options>>]

Output information about which build system would be used for a particular build step.  The build step
must be one of B<configure>, B<build>, B<test>, B<install> or B<clean> and must be the first argument
after B<which-build-system> when provided.  If omitted, it defaults to B<configure> as it is the
most reliable step to use auto-detection on in a clean source directory.  Note that build steps do not
always agree when using auto-detection - particularly if the B<configure> step has not been run.

Additionally, the B<clean> step can also provide "surprising" results for builds that rely on
a separate build directory.  In such cases, debhelper will return the first build system that
uses a separate build directory rather than the one build system that B<configure> would detect.
This is generally a cosmetic issue as both build systems are all basically a glorified
B<rm -fr builddir> and more precise detection is functionally irrelevant as far as debhelper is
concerned.

The option accepts all debhelper build system arguments - i.e., options you can pass to all of
the B<dh_auto_*> commands plus (for the B<install> step) the B<--destdir> option.  These options
affect the output and auto-detection in various ways.  Passing B<-S> or B<--buildsystem>
overrides the auto-detection (as it does for B<dh_auto_*>) but it still provides introspection
into the chosen build system.

Things that are useful to know about the output:

=over 4

=item *

The key B<build-system> is the build system that would be used by debhelper for the given
step (with the given options, debhelper compat level, environment variables and the given
working directory).  When B<-S> and B<--buildsystem> are omitted, this is the result of
debhelper's auto-detection logic.

The value is valid as a parameter for the B<--buildsystem> option.

The special value B<none> is used to denote that no build system would be used.  This value
is not present in B<--list> parameter for the B<dh_auto_*> commands, but since debhelper/12.9
the value is accepted for the B<--buildsystem> option.

Note that auto-detection is subject to limitations in regards to third-party build systems.
While debhelper I<does> support auto-detecting some third-party build systems, they must be
installed for the detection to work.  If they are not installed, the detection logic silently
skips that build system (often resulting in B<build-system> being B<none> in the output).

=item *

The B<build-directory> and B<buildpath> values serve different but related purposes.  The
B<build-directory> generally mirrors the B<--builddirectory> option where as B<buildpath>
is the output directory that debhelper will use.  Therefore the former will often be null
when B<--builddirectory> has not been passed while the latter will generally not be null
(except when B<build-system> is B<none>).

=item *

The B<dest-directory> (B<--destdir>) is undefined for all build steps except the B<install> build
step (will be output as null or absent).  For the same reason, B<--destdir> should only be
passed for B<install> build step.

Note that if not specified, this value is currently null by default.

=item *

The B<parallel> value is subject to B<DEB_BUILD_OPTIONS>.  Notably, if that does not include
the B<parallel> keyword, then B<parallel> field in the output will always be 1.

=item *

Most fields in the output I<can> be null.  Particular if there is no build system is detected
(or when B<--buildsystem=none>).  Additionally, many of the fields can be null even if there
is a build system if the build system does not use/set/define that variable.

=back

=head2 detect-hook-targets (EXEC, AJSON)

B<Synopsis>: B<dh_assistant> B<detect-hook-targets>

Detects possible override targets and hook targets that L<dh(1)> might use (provided that the
relevant command is in the sequence).

**UNSAFE**: This command relies on the output of L<make>. Even it its dry-run mode, B<make> may
execute commands from F<debian/rules>. Avoid using on packages from untrusted sources, where you
have not reviewed the packaging for backdoors.

The detection is based on scanning the rules file for any target that I<might look> like a hook
target and can therefore list targets that are in fact not hook targets (or are but will never
be triggered for other reasons).

The detection uses a similar logic for scanning the rules file and is therefore subject to
makefile conditionals (i.e., the truth value of makefile conditionals can change whether a hook
target is visible in the output of this command).  In theory, you would have to setup up the
environment to look like it would during a build for getting the most accurate output.  Though,
a lot of packages will not have conditional hook targets, so the "out of the box" behaviour
will work well in most cases.

The output looks something like this:

    {
       "commands-not-in-path": [
          "dh_foo"
       ],
       "hook-targets": [
          {
             "command": "dh_strip_nondeterminism",
             "is-empty": true,
             "package-section-param": null,
             "filename": "debian/rules",
             "target-name": "override_dh_strip_nondeterminism"
          },
          {
             "command": "dh_foo",
             "is-empty": false,
             "package-section-param": "-a",
             "filename": "debian/rules",
             "target-name": "override_dh_foo-arch"
          }
       ]
    }

In more details:

=over 4

=item commands-not-in-path

This attribute lists all the commands related to hook targets, which B<dh_assistant> could B<not>
find in PATH.  These are usually caused by either the command not being installed on the system
where B<dh_assistant> is run or by the command not existing at all.

If you are using this command to verify an hook target is present, please double check that the
command is spelled correctly.

=item hook-targets

List over hook targets found along with additional information about them.

=over 4

=item command

Attribute that lists which command this hook target is related too.

=item target-name

The actual target name detected in the F<debian/rules> file.

=item is-empty

A boolean that determines whether L<dh(1)> will optimize the hook out at runtime (see "Completely empty targets" in
L<dh(1)>). Note that empty override targets will still cause L<dh(1)>  to skip the original command.

=item package-section-param

This attribute defines what package selection parameter should be passed to B<dh_*> commands used
in the hook target.  It can either be B<-a>, B<-i> or (if no parameter should be used) C<null>.

=item filename

This attribute reports which file the target was found it. In most cases, this will always be "debian/rules"
though in case of include files, the target could appear in an include file.  Note this attribute is not
super reliable as L<make(1)> only reports it for targets with a "recipe" (targets with commands inside
them). When B<make> does not provide the filename, B<dh_assistant> blindly assumes the filename is
"debian/rules" (as overrides via includes is not a commonly used feature).

Note this accuracy of this attribute is limited about what data B<dh_assistant> can read out from the
following command:

    LC_ALL=C make -Rrnpsf debian/rules debhelper-fail-me 2>/dev/null

=back

=back

This command accepts no options or arguments.


=head2 detect-unknown-hook-targets (EXEC, AJSON, LINT)

B<Synopsis>: B<dh_assistant> B<detect-unknown-hook-targets> [--output-format=json] [command-options]

Detects unknown and possibly misspelled override targets and hook targets in F<debian/rules> that
will most likely not be used by L<dh(1)>.

**UNSAFE**: This command relies on the output of L<make>. Even it its dry-run mode, B<make> may
execute commands from F<debian/rules>. Avoid using on packages from untrusted sources, where you
have not reviewed the packaging for backdoors.

This command differs from B<detect-hook-targets> subtly in the scope. The B<detect-hook-targets>
will list all targets that looks like hook targets whether they are applicable or not. This
command show all hook targets, for which a command cannot be found in any sequence. Accordingly,
this command is better for linting purposes whereas B<detect-hook-targets> is better if you want
to know which hook targets are present. All the limitations listed in B<detect-hook-targets>
about scanning the rules file apply equally to this command.

This command will attempt will attempt to load any sequence add-on listed via build-dependencies
and therefore these must be installed. Additional modules can be passed via B<--with> like with
L<dh(1)> as needed.

This command will also need one of the following perl modules to be available:
L<Text::Levenshtein>, L<Text::LevenshteinXS>, L<Text::Levenshtein::XS>. The first one can be
installed via B<apt install libtext-levenshtein-perl>.

The text output is intended for human consumption and should be self-explanatory.  Since it is
not stable, it will not be documented. The JSON output looks something like this:

    {
       "unknown-hook-targets": [
          {
             "target-name": "execute_before_dh_instlal",
             "filename": "debian/rules",
             "candidates": [
                "execute_before_dh_install"
             ]
          }
       ]
    }

In more details:

=over 4

=item unknown-hook-targets

List of all the unknown hook targets found along with additional information about them.

=over 4

=item target-name

The actual target name detected in the file (usually F<debian/rules>).

=item filename

This attribute reports which file the target was found it. In most cases, this will always be "debian/rules"
though in case of include files, the target could appear in an include file.  Note this attribute is not
super reliable as L<make(1)> only reports it for targets with a "recipe" (targets with commands inside
them). When B<make> does not provide the filename, B<dh_assistant> blindly assumes the filename is
"debian/rules" (as overrides via includes is not a commonly used feature).

Note this accuracy of this attribute is limited about what data B<dh_assistant> can read out from the
following command:

    LC_ALL=C make -Rrnpsf debian/rules debhelper-fail-me 2>/dev/null

=item candidates

When not null and not empty, each element in this list are names for likely candidates for the
"correct" name of this target.

=item filename

=back

=item issues

If present, then it is a list of one or more reasons why this output is definitely incomplete. Each element
in the list is an object with the following keys:

=over 4

=item issue

A key defining the issue. Currently, it is always B<load-addon>, which signals that B<dh_assistant> could
not load the add-on listed in the B<addon> key.

Parsers should assume new issue types may appear in the future.

=item addon

If present, it defines the name of a B<dh> sequence add-on that is related to the failure.

=back

=back

This command accepts the following options:

=over 4

=item B<--output-format=>I<FORMAT>

Request a certain type of output format. Valid values are B<text> or B<json>.

The text format is intended for human consumption and may change between versions without any
regard for machine consumption. If you want to use this command for machine consumption, please
use the JSON format.

=item B<--no-linter-exit-code>, B<--linter-exit-code>

These options control whether the command should exit with the linter exit code (2) or not (0)
when an unknown target is found. By default, it uses the linter exit code when an unknown target
is found.

=item B<--with> I<addon>, B<--without> I<addon>

These options behave the same as the L<dh(1)> options with the same name.

=back

=head2 list-commands (RJSON)

B<Synopsis>: B<dh_assistant> B<list-commands> [--output-format=json] [command-options]

Load all B<dh> sequence add-ons and extract a full list of all commands that will be invoked across
all sequences. The command makes no attempt to filter out commands that will not be run due to
override targets or due to certain sequences not being run (by B<dh> or at all).

As the command will attempt to load all plugins, they must be installed.

The text output is intended for human consumption and should be self-explanatory.  Since it is
not stable, it will not be documented. The JSON output looks something like this:

    {
       "commands": [
          {
             "command": "dh_auto_build"
          },
          {
             "command": "dh_auto_clean"
          },
          [... more commands listed here... ]
       ],
       "issues": [
            {
                "issue": "load-addon",
                "addon": "foo"
            }
       ]
    }

=over 4

=item commands

The top level key containing the list of all commands. Each element in the list are an object and
can have the following keys:

=over 4

=item command

The name of the command.

While most commands are resolved via PATH, a sequence add-on could register a command via a full path
(by passing the path search). If so, the command provided in this output will also use the full path.

=back

=item issues

If present, then it is a list of one or more reasons why this output is definitely incomplete. Each element
in the list is an object with the following keys:

=over 4

=item issue

A key defining the issue. Currently, it is always B<load-addon>, which signals that B<dh_assistant> could
not load the add-on listed in the B<addon> key.

Parsers should assume new issue types may appear in the future.

=item addon

If present, it defines the name of a B<dh> sequence add-on that is related to the failure.

=back

=back

This command accepts the following options:

=over 4

=item B<--output-format=>I<FORMAT>

Request a certain type of output format. Valid values are B<text> or B<json>.

The text format is intended for human consumption and may change between versions without any
regard for machine consumption. If you want to use this command for machine consumption, please
use the JSON format.

=item B<--with> I<addon>, B<--without> I<addon>

These options behave the same as the L<dh(1)> options with the same name.

=back

=head2 list-guessed-dh-config-files (AJSON)

B<Synopsis>: B<dh_assistant> B<list-guessed-dh-config-files> [command-options]

Load all B<dh> sequence add-ons, determine the full list of commands could be used by this
source package and for each command used, then attempt to I<guess> which "config files"
these commands are interested in.

Note this command only guesses "per command config files". Standard global config files
such as F<debian/control>, F<debian/rules>, and F<debian/compat> are not included in this
output.

As the command name implies, the resulting output is not a full list (and will never be).
The B<dh_assistant> tool have to derive this from optional metadata that commands can
choose to provide and B<dh_assistant> has no means to validate that this metadata is up
to date.

As the command will attempt to load all plugins, they must be installed.

The text output is intended for human consumption and should be self-explanatory.  Since it is
not stable, it will not be documented. The JSON output looks something like this:

    {
       "config-files": [
          {
             "commands": [
                {
                   "command": "dh_autoreconf_clean"
                }
             ],
             "file-type": "pkgfile",
             "pkgfile": "autoreconf.before"
          },
          {
             "commands": [
                {
                   "command": "dh_installgsettings"
                }
             ],
             "file-type": "pkgfile",
             "pkgfile": "gsettings-override"
          },
          # [ ... more entries here ...]
       ],
       "issues": [
           {
                "issue": "load-addon",
                "addon": "foo"
           }
       ]
    }


=over 4

=item config-files

The top level key containing the list of all config-files. Each element in the list are an object and
can have the following keys:

=over 4

=item file-type

The type of config file detected. At the time of writing, this will always be B<pkgfile>. However,
other values may appear in the future.

The B<pkgfile> key means that the config file is a B<debhelper pkgfile> (named after the B<pkgfile> sub
in L<Debian::Debhelper::Dh_Lib> that locates the file).

=item pkgfile

When B<file-type> is B<pkgfile>, this key defines the name stem of the B<pkgfile>. An example, this will
be B<install> for L<dh_install(1)>'s config file and B<docs> for L<dh_installdocs(1)>'s config file.

When B<file-type> is B<not> B<pkgfile>, then this key will be absent.

Typically names for these files are:

     debian/PKGFILE
     debian/PACKAGE.PKGFILE

However, there are more variants caused by B<--name> plus architecture specific suffixes.

=item internal

This key may exist and any value for it is not standardized. Use at own peril.

It used for document certain specific implementation details such as bug compatibility and may change
as the situation changes.

=item commands

This key will be a list with each element in it being an object with the following keys:

=over 4

=item command

Name of the command that is interested in this config file. Multiple commands can be interested in the same
config file. An example of this would be B<dh_installinit>, B<dh_installsystemd> and B<dh_installtmpfiles>,
which all reacts to (the now) deprecated B<tmpfile> pkgfile. In the particular case, only one command reacts
to the file for a given compat level (but that information is not available to B<dh_assistant> and therefore
is not available in this output either).

=back

=back

=item issues

If present, then it is a list of one or more reasons why this output is definitely incomplete. Each element
in the list is an object with the following keys:

=over 4

=item issue

A key defining the issue. Currently, it is always B<load-addon>, which signals that B<dh_assistant> could
not load the add-on listed in the B<addon> key.

Parsers should assume new issue types may appear in the future.

=item addon

If present, it defines the name of a B<dh> sequence add-on that is related to the failure.

=back

=back

This command accepts the following options:

=over 4

=item B<--with> I<addon>, B<--without> I<addon>

These options behave the same as the L<dh(1)> options with the same name.

=back

=head2 log-installed-files (BLD)

B<Synopsis>: B<dh_assistant> B<log-installed-files> B<< -pI<pkg> >> I<[--on-behalf-of-cmd=dh_foo]> B<path ...>

Mark one or more paths as installed for a given package.  This is useful for telling L<dh_missing(1)> that the
paths have been installed manually.

The B<--on-behalf-of-cmd> option can be used by third-party tools to have B<dh_assistant> list them as the
installer of the provided paths.  The convention is to use the basename of the tool itself as its name
(e.g. B<dh_install>).

Please keep in mind that:

=over 4

=item *

B<No> glob or substitution expansion is done by B<dh_assistant> on the provided paths.  If you want to use globs,
have the shell perform the expansion first.

=item *

Paths must be given as relative to the source root directory (e.g., F<debian/tmp/...>)

=item *

You I<can> provide a directory.  If you do, the directory and anything recursively below it will be considered
as installed.  Note that it is fine to provide the directory even if paths inside of it has been excluded as long
as the directory is fully "covered".

=item *

Do not worry about providing the same filename twice in different invocations to B<dh_assistant> due to B<-arch> /
B<-indep> overrides.  While it will be recorded multiple internally, L<dh_missing(1)> will deduplicate when it
parses the records.

=back

Note this command only I<marks> paths as installed. It does not actually install them - the caller should ensure
that the paths are in fact handled (or installed).

=head2 restore-file-on-clean (BLD)

B<Synopsis>: B<dh_assistant> B<restore-file-on-clean> B<FILE ...>

This command will take a backup of listed files and tell L<dh_clean(1)> to restore them when it runs.

Note that generally you do not need to restore modified files on clean. Often you can get away with just
removing them if they are regenerated anyway (which is the most common case for files being modified during
builds).  Use this command when something taints a file and the build does not cope with the file being
removed.

The file is stored in B<debian/.debhelper>. If you remove this directory manually without calling
L<dh_clean(1)> then your B<dh_assistant> provided backup is gone permanently and the restore will never
occur. At this point, only a version control system or another backup can restore the files.

The command has the following limitations:

=over 4

=item No thread-safety - concurrency will corrupt the restore

The command relies on updating an internal index and concurrent writes will cause it to be corrupt.

While most B<dh_*> commands does not use the underlying function, any of them could do so. Avoid running
another B<dh_*> command while B<dh_assistant> processes this command (especially running multiple concurrent
instances of B<dh_assistant restore-file-on-clean> is asking for corruption!).

=item Files only, not directories nor symlinks to files

This command will only restore files; not directories or symlinks to files. It will reject any non-files.

Additionally, if the directory containing the file is removed, the restore will fail (as B<debhelper>
does not track the directory, it cannot restore it reliably). If this happens, you can do a B<mkdir>
to restore the directory and run L<dh_clean(1)> again to get the files back. After that, consider
what went wrong and whether you are using the correct tool(s).

=item Strict file names

All filenames must be relative to the package root (without using the B<./> prefix). No hidden files (that
is any file starting with a period B<.>) and no version control directories (such as B<CVS>). The checks
are best effort.

These checks are here to ensure you do not accidentally trash important data that would help you undo
mistakes.

=item Heavy duty

The command takes a B<full copy> of all files you pass it. This is fine for a handful of small files,
which is the intended use-case. If you find yourself passing 10+ files or very large files, you might
be applying a sledgehammer where you needed a different tool.

=back

=head2 supports (CFFA)

B<Synopsis>: B<dh_assistant> B<supports> B<COMMAND>

This command is a scripting aid to programmatically determine whether B<dh_assistant> knows about a given
subcommand. Pass the name of a subcommand and this command will exit successfully if the subcommand was known
and unsuccessfully otherwise.

=head1 COMMAND TAGS

Most commands have one or more of the following "tags" associated with them.  Their
meaning is defined here.

=over 4

=item EXEC

This command will or may execute content from the package. Do not run on untrusted packages.

Note: This tag only applies if the command will I<out of the box> be unsafe. As an example, commands that
parse the output of B<make> is inherently unsafe, because it is trivial B<make> to have B<make> run
code even in B<--dry-run> mode. As a counter example, commands that only loads B<dh> add-ons will be
considered safe, because B<PERL5LIB> is assumed to be curated to only include trusted plugins.

=item AJSON

The command always provides JSON output. See L</JSON OUTPUT> for details.

=item OJSON

The command *can* provide JSON output via B<--output-format=json>, but does not
do so by default. See L</JSON OUTPUT> for details when using B<--output-format=json>.

=item LINT

The command is or can be used for linting purposes. This command will exit with code 2 when an important
issue is found. B<Be careful> if the command is also tagged with B<EXEC>. When this happens, the
command should only be used on trusted content.

Note that commands may have options that redefine what is considered an "important" issue.

=item CRFA

I<Mnemonic "Can be Run From Anywhere">

Most commands must be run inside a source package root directory (a directory
containing F<debian/control>) because debhelper will need the package metadata
to lookup the information.  Any command with this tag are exempt from this
requirement and is expected to work regardless of where they are run.

=item BLD

The command is intended to be used as a part of a package build. It may leave
artifacts behind that will need a L<dh_clean(1)> invocation to remove.

=back

=head1 JSON OUTPUT

Most commands uses JSON format as output.  Consumers need to be aware that:

=over 4

=item *

Additional keys may be added at any time.  For backwards compatibility, the absence
of a key should in general be interpreted as null unless another default is documented
or would be "obvious" for that case.

=item *

Many keys can be null/undefined in special cases.  As an example, some information may
be unavailable when this command is run directly from the debhelper source (git repository).

=back

The output will be prettified when stdout is detected as a terminal.  If
you need to pipe the output to a pager/file (etc.) and still want it
prettified, please use an external JSON formatter. An example of this:

     dh_assistant supported-compat-levels | json_pp | less

=cut

my $JSON_ENCODER = JSON::PP->new->utf8;

# Prettify if we think the user is reading this.
$JSON_ENCODER = $JSON_ENCODER->pretty->space_before(0)->canonical if -t STDOUT;

# We never use the log file for this tool
inhibit_log();
$Debian::Debhelper::Dh_Lib::PARSE_DH_SEQUENCE_INFO = 1;
# Force commands to opt-in
$Debian::Debhelper::Dh_Lib::ALLOW_UNSAFE_EXECUTION = 0;


my %COMMANDS = (
    'help'                         => \&_do_help,
    '-h'                           => \&_do_help,
    '--help'                       => \&_do_help,
    'active-compat-level'          => \&active_compat_level,
    'supported-compat-levels'      => \&supported_compat_levels,
    'which-build-system'           => \&which_build_system,
    'detect-hook-targets'          => \&detect_hook_targets,
    'detect-unknown-hook-targets'  => \&detect_unknown_hook_targets,
    'list-commands'                => \&list_commands,
    'list-guessed-dh-config-files' => \&list_guessed_dh_config_files,
    'log-installed-files'          => \&log_installed_files_cmd,
    'restore-file-on-clean'        => \&dh_assistant_restore_file_on_clean,
    'supports'                     => \&supports,
);

my ($COMMAND) = shift(@ARGV);
for my $arg (@ARGV) {
    if ($arg eq '--help' or $arg eq '-h') {
        $COMMAND = 'help';
        last;
    }
}


sub _do_help {
    my $me = basename($0);
    print <<"EOF";
${me}: Tool for supporting debhelper tools and provide introspection

Usage: ${me} <command> [... addition arguments or options ...]

The following commands are available:
  help                       Show this help
  active-compat-level        Output information about which compat level is declared/active (AJSON)
  supported-compat-levels    Output information about supported compat levels (AJSON, CRFA)
  which-build-system         Determine which build system will be used (AJSON)
  detect-hook-targets        Detect and output possible override and hook targets (EXEC, AJSON)
  detect-unknown-hook-targets
                             Detect unknown / typos of known hook targets (EXEC, RJSON)
  list-commands              List all commands across all sequences (RJSON)
  list-guessed-dh-config-files
                             List guessed "config files" for debhelper commands (AJSON)
  log-installed-files        Mark one or more paths as "installed" so dh_missing is aware (BLD)
  restore-file-on-clean      Mark one or more files as to be restored by dh_clean (BLD)
  supports                   Script aid: Test whether dh_assistant knows a particular command (CRFA)

Command tags:

 * EXEC    *UNSAFE*: The command may execute code from the package. Do not use on unsafe content.
 * AJSON   The command always provides JSON output.
 * RJSON   The command *can* provide JSON output via --output-format=json.
 * LINT    The command is or can be used for linting purposes. This command will exit with code 2
           when an important issue is found.
 * CRFA    Command does not need to be run from a package source directory
           (Mnemonic "Can be Run From Anywhere")
 * BLD     The command is intended to be used as a part of a package build.
           It may leave artifacts behind that will need a dh_clean invocation to remove.


Its primary purpose is to provide support for third-party debhelper implementations
not using the debhelper script API or provide introspection for third-party tools
(e.g., linters).  Unless stated otherwise, commands must be run inside a source
package root directory - that is, the directory containing "debian/control".

Most commands use or can provide JSON output.  When stdout is a TTY, the JSON will be
prettified. See the manpage if you want formatting in other cases.
EOF
    return;
}

sub _assert_debian_control_exists {
    return if -f 'debian/control';
    require Cwd;
    my $cwd = Cwd::getcwd();
    warning("$cwd does not look like a package source directory (expected $cwd/debian/control to exist and be a file)");
    error("$COMMAND must be run inside a package source directory");
    return;
}

sub _output {
    my ($kvpairs) = @_;
    print $JSON_ENCODER->encode($kvpairs);
    return;
}

sub _allow_unsafe_execution() {
    $Debian::Debhelper::Dh_Lib::ALLOW_UNSAFE_EXECUTION = 1;
}

sub active_compat_level {
    if (@ARGV) {
        error("$COMMAND: No arguments supported (please remove everything after the command)");
    }
    _assert_debian_control_exists();
    my ($active_compat, $declared_compat, $declared_compat_source) = Debian::Debhelper::Dh_Lib::get_compat_info();
    if (not defined($declared_compat_source)) {
        $declared_compat = undef;
        $active_compat = undef if not exists($ENV{DH_COMPAT});
    }
    my %compat_info = (
        'active-compat-level'          => $active_compat,
        'declared-compat-level'        => $declared_compat,
        'declared-compat-level-source' => $declared_compat_source,
    );
    _output(\%compat_info);
    return;
}

sub supported_compat_levels {
    if (@ARGV) {
        error("$COMMAND: No arguments supported (please remove everything after the command)");
    }
    my %compat_levels = (
        'MIN_COMPAT_LEVEL'                           => Debian::Debhelper::Dh_Lib::MIN_COMPAT_LEVEL,
        'LOWEST_NON_DEPRECATED_COMPAT_LEVEL'         => Debian::Debhelper::Dh_Lib::LOWEST_NON_DEPRECATED_COMPAT_LEVEL,
        'LOWEST_VIRTUAL_DEBHELPER_COMPAT_LEVEL'      => Debian::Debhelper::Dh_Lib::LOWEST_VIRTUAL_DEBHELPER_COMPAT_LEVEL,
        'MAX_COMPAT_LEVEL'                           => Debian::Debhelper::Dh_Lib::MAX_COMPAT_LEVEL,
        'HIGHEST_STABLE_COMPAT_LEVEL'                => Debian::Debhelper::Dh_Lib::HIGHEST_STABLE_COMPAT_LEVEL,
        'MIN_COMPAT_LEVEL_NOT_SCHEDULED_FOR_REMOVAL' => Debian::Debhelper::Dh_Lib::MIN_COMPAT_LEVEL_NOT_SCHEDULED_FOR_REMOVAL,
    );
    _output(\%compat_levels);
    return;
}

sub which_build_system {
    my ($opt_buildsys, $destdir);
    my $first_argv = @ARGV ? $ARGV[0] : '';
    my %options = (
        # Emulate dh_auto_install's --destdir
        "destdir=s" => \$destdir,
    );
    _assert_debian_control_exists();
    # We never want the build system initialization to modify anything (e.g. create "HOME")
    $dh{NO_ACT} = 1;
    require Debian::Debhelper::Dh_Buildsystems;
    Debian::Debhelper::Dh_Buildsystems::buildsystems_init(options => \%options);
    my @non_options = grep { !m/^-/ } @ARGV;
    my $step = @non_options ? $non_options[0] : 'configure';
    if (@non_options && $first_argv =~ m/^-/) {
        error("$COMMAND: If the build step is provided, it must be before any options");
    }
    if (@non_options > 1) {
        error("$COMMAND: At most one positional argument is supported");
    }
    if (defined($destdir) and $step ne 'install') {
        warning("$COMMAND: --destdir is not defined for build step \"$step\". Ignoring option")
    }
    {
        no warnings qw(once);
        $opt_buildsys = $Debian::Debhelper::Dh_Buildsystems::opt_buildsys;
    }
    my $build_system = Debian::Debhelper::Dh_Buildsystems::load_buildsystem($opt_buildsys, $step);
    my %result = (
        'build-system'       => defined($build_system) ? $build_system->NAME : 'none',
        'for-build-step'     => $step,
        'source-directory'   => defined($build_system) ? $build_system->get_sourcedir : undef,
        'build-directory'    => defined($build_system) ? $build_system->get_builddir : undef,
        'dest-directory'     => defined($build_system) ? $destdir : undef,
        'buildpath'          => defined($build_system) ? $build_system->get_buildpath : undef,
        'parallel'           => defined($build_system) ? $build_system->get_parallel : undef,
        'upstream-arguments' => $dh{U_PARAMS},
    );
    _output(\%result);
    return;
}

sub _in_path {
    my ($cmd) = @_;
    for my $dir (split(':', $ENV{PATH})) {
        return 1 if -x "${dir}/${cmd}";
    }
    return 0;
}

sub _load_hook_targets {
    require Debian::Debhelper::SequencerUtil;
    Debian::Debhelper::SequencerUtil::rules_explicit_target('does-not-matter');
    my ($explicit_targets);
    {
        no warnings qw(once);
        $explicit_targets = \%Debian::Debhelper::SequencerUtil::EXPLICIT_TARGETS;
    }
    return $explicit_targets;
}

sub _hook_target_variants {
    my ($name) = @_;
    my @base = (
        "override_${name}",
        "execute_before_${name}",
        "execute_after_${name}",
    );
    return map {
        (
            $_,
            "${_}-arch",
            "${_}-indep",
        )
    } @base;
}


sub _load_levenshtein {
    my @modules = (qw(
        Text::LevenshteinXS
        Text::Levenshtein::XS
        Text::Levenshtein
    ));
    my $err;
    for my $module (@modules) {
        my $distance_func = eval "use $module (); \\&${module}::distance";
        $err = $@;
        if (defined($distance_func)) {
            return $distance_func;
        }
    }
    my $module_names = join(', ', @modules);
    warning("Could not load any of the modules ${module_names}");
    warning("Usually, `apt install libtext-levenshtein-perl` will fix this problem.");
    error("This subcommand requires one of the following modules to be available: ${module_names}. Last failure was: $@");
}


sub _all_sequence_commands {
    my ($forgive_errors, @addon_requests) = @_;
    my ($sequences, @all_commands, @unloadable);
    Debian::Debhelper::SequencerUtil::load_sequence_addon('root-sequence', 'both');
    my @addons = Debian::Debhelper::SequencerUtil::compute_selected_addons('binary', @addon_requests);
    # Load addons, which can modify sequences.
    foreach my $addon (@addons) {
        my $addon_name = $addon->{'name'};
        my $addon_type = $addon->{'addon-type'};
        eval {
            Debian::Debhelper::SequencerUtil::load_sequence_addon($addon_name, $addon_type);
        };
        if (my $err = $@) {
            die($err) if not $forgive_errors;
            push(@unloadable, $addon_name);
        }
    }
    {
        no warnings qw(once);
        $sequences = \%Debian::Debhelper::DH::SequenceState::sequences;
    }
    my %seen;
    for my $sequence(values(%{$sequences})) {
        my @commands = map {$_->[0]} $sequence->flatten_sequence('both', 0);
        for my $command (@commands) {
            next if $command =~ m{^(?:debian/rules|create-stamp)};
            next if exists($seen{$command});
            $seen{$command} = 1;
            push(@all_commands, $command);
        }
    }
    return \@all_commands, \@unloadable;
}

sub list_commands {
    _assert_debian_control_exists();
    require Getopt::Long;
    Getopt::Long::config('no_ignore_case');
    require Debian::Debhelper::SequencerUtil;
    my $output_format = "text";
    my (@addon_requests);
    my %options=(
        "output-format=s" => \$output_format,
        "with=s" => sub {
			my ($option, $value) = @_;
			push(@addon_requests, map { "+${_}" } split(",", $value));
		},
		"without=s" => sub {
			my ($option, $value) = @_;
			push(@addon_requests, map { "-${_}" } split(",", $value));
		},
	);
    Getopt::Long::GetOptionsFromArray(\@ARGV, %options)
        or error("Could not parse the arguments");

    if (@ARGV) {
        my $value = $ARGV[0];
        error("$COMMAND: No non-options supported - please remove ${value}");
    }

    my ($all_commands, $unloadables) = _all_sequence_commands(1, @addon_requests);
    if ($output_format eq 'json') {
        my @commands_json;
        for my $command (sort(@{$all_commands})) {
            push(@commands_json, {
                'command' => $command,
            });
        }
        my %result = (
            "commands" => \@commands_json,
        );
        if (@{$unloadables}) {
            my @issues;
            for my $addon (@{$unloadables}) {
                push(@issues, {
                    "issue" => "load-addon",
                    "addon" => $addon,
                });
            };
            $result{'issues'} = \@issues;
        }
        _output(\%result);
    } elsif ($output_format eq 'text') {
        print("Commands present in at least one sequence for this source package (sorted by name):\n");
        for my $command (sort(@{$all_commands})) {
            print("\t${command}\n");
        }
        if (@{$unloadables}) {
            my $addon_names = join(" ", @{$unloadables});
            print("\n");
            warning("Incomplete result. The following sequence add-ons could not be loaded: $addon_names");
        }
    } else {
        error("Internal error: Missing case for ${output_format}");
    }
}

sub _extract_annotations {
    my ($command) = @_;
    my @annotations;

	foreach my $dir (split(':', $ENV{PATH})) {
		if (open (my $h, "<", "$dir/$command")) {
			while (<$h>) {
				if (m/PROMISE: DH NOOP( WITHOUT\s+(.*))?\s*$/) {
					if (defined($2)) {
                        push(@annotations, split(' ', $2));
                    } else {
                        push(@annotations, 'always-skip');
                    }
				}
                if (m/INTROSPECTABLE: CONFIG-FILES\s+(.*)\s*$/) {
                    push(@annotations, split(' ', $1));
                }
			}
			close $h;
			return @annotations;
		}
	}
	return;
}

sub list_guessed_dh_config_files {
    _assert_debian_control_exists();
    require Getopt::Long;
    Getopt::Long::config('no_ignore_case');
    require Debian::Debhelper::SequencerUtil;
    my (@addon_requests);
    my %options=(
        "with=s" => sub {
			my ($option, $value) = @_;
			push(@addon_requests, map { "+${_}" } split(",", $value));
		},
		"without=s" => sub {
			my ($option, $value) = @_;
			push(@addon_requests, map { "-${_}" } split(",", $value));
		},
	);
    Getopt::Long::GetOptionsFromArray(\@ARGV, %options)
        or error("Could not parse the arguments");

    if (@ARGV) {
        my $value = $ARGV[0];
        error("$COMMAND: No non-options supported - please remove ${value}");
    }

    my ($all_commands, $unloadables) = _all_sequence_commands(1, @addon_requests);
    my $pkg_files = {};
    my $bug_950723;
    for my $command (@{$all_commands}) {
        my @annotations = _extract_annotations($command);
        next if not @annotations or $annotations[0] eq 'always-skip';
        for my $annotation (@annotations) {
            my $type = 'pkgfile';
			my $need = $annotation;
			if ($annotation =~ m/^([a-zA-Z0-9-_]+)\((.*)\)$/) {
				($type, $need) = ($1, $2);
			}
			if ($type eq 'internal') {
				$bug_950723 = 1 if $need eq 'bug#950723';
			}
            next if $type ne 'pkgfile' and $type ne 'pkgfile-logged';
            my $key = "pkgfile/${need}";
            my $existing = $pkg_files->{$key};
            if (defined($existing)) {
                push(@{$existing->{'commands'}}, {
                    'command' => $command,
                });
            } else {
                $existing = {
                    'file-type' => 'pkgfile',
                    'pkgfile'   => $need,
                    'commands'  => [{
                        'command' => $command,
                    }],
                };
                $pkg_files->{$key} = $existing;
            }
            if ($bug_950723) {
                $existing->{"internal"}{"bug#950723"} = JSON::PP::true;
            }
        }
    }

    my @config_files = values(%{$pkg_files});
    my %result = (
        "config-files" => \@config_files,
    );
    if (@{$unloadables}) {
        my @issues;
        for my $addon (@{$unloadables}) {
            push(@issues, {
                "issue" => "load-addon",
                "addon" => $addon,
            });
        };
        $result{'issues'} = \@issues;
    }
    _output(\%result);
}


sub detect_unknown_hook_targets {
    _assert_debian_control_exists();
    _allow_unsafe_execution();
    my $distance_func = _load_levenshtein();
    require Getopt::Long;
    Getopt::Long::config('no_ignore_case');
    require Debian::Debhelper::SequencerUtil;
    my $output_format = "text";
    my (@addon_requests, %all_overrides, %unknown_hooks);
    my $lint_exit = 1;
    my %options=(
        "output-format=s" => \$output_format,
        "linter-exit-code!" => \$lint_exit,
        "with=s" => sub {
			my ($option, $value) = @_;
			push(@addon_requests, map { "+${_}" } split(",", $value));
		},
		"without=s" => sub {
			my ($option, $value) = @_;
			push(@addon_requests, map { "-${_}" } split(",", $value));
		},
	);

    Getopt::Long::GetOptionsFromArray(\@ARGV, %options)
        or error("Could not parse the arguments");
    if ($output_format ne 'text' and $output_format ne 'json') {
        error("--output-format must be either text or json\n");
    }
    if (@ARGV) {
        my $value = $ARGV[0];
        error("$COMMAND: No non-options supported - please remove ${value}");
    }
    my $explicit_targets = _load_hook_targets();
    my %missing_targets = map {
        $_ => 1
    } grep {
        $_ ne 'debhelper-fail-me' and !m{^(?:debian/rules|create-stamp)}
    } keys(%{$explicit_targets});

    my ($all_commands, $unloadables) = _all_sequence_commands(1, @addon_requests);
    for my $command (@{$all_commands}) {
        for my $variant (_hook_target_variants($command)) {
            $all_overrides{$variant} = 1;
            delete($missing_targets{$variant});
        }
    }
    my @variants = sort(keys(%all_overrides));
    for my $target (keys(%missing_targets)) {
        my @closest_variants;
        my $closest_variant_distance = 9999;
        for my $variant (@variants) {
            next if abs(length($target) - length($variant)) > 3;
            my $dist = $distance_func->($target, $variant);
            next if $dist > $closest_variant_distance or $dist > 3;
            if ($dist < $closest_variant_distance) {
                $closest_variant_distance = $dist;
                @closest_variants = ();
            }
            push(@closest_variants, $variant);
        }
        next if not @closest_variants and $target !~ m{^(?:override|execute_before|execute_after)_};
        @closest_variants = sort(@closest_variants);
        $unknown_hooks{$target} = \@closest_variants;
    }

    if ($output_format eq 'json') {
        my @hook_target_data;
        for my $target (sort(keys(%unknown_hooks))) {
            my $options = $unknown_hooks{$target};
            my (undef, $filename) = @{$explicit_targets->{$target}};
            push(@hook_target_data, {
                'target-name' => $target,
                'filename'  => $filename,
                'candidates'  => $options,
            });
        }
        my %result = (
            "unknown-hook-targets" => \@hook_target_data,
        );
        if (@{$unloadables}) {
            my @issues;
            for my $addon (@{$unloadables}) {
                push(@issues, {
                    "issue" => "load-addon",
                    "addon" => $addon,
                });
            };
            $result{'issues'} = \@issues;
        }
        _output(\%result);
    } elsif ($output_format eq 'text') {
        for my $target (sort(keys(%unknown_hooks))) {
            my $options = $unknown_hooks{$target};
            my (undef, $filename) = @{$explicit_targets->{$target}};
            my $help = '';
            if (@{$options}) {
                if (scalar(@{$options}) == 1) {
                    my $name = $options->[0];
                    $help = " Likely a typo of ${name}";
                } else {
                    my $names = join(', ', @{$options});
                    $help = " Likely a typo of one of ${names}";
                }
            }
            print("The hook target ${target} in ${filename} does not seem to match any known commands. ${help}\n");
        }
        if (@{$unloadables}) {
            my $addon_names = join(" ", @{$unloadables});
            print("\n");
            warning("Incomplete result. The following sequence add-ons could not be loaded: $addon_names");
        }
    } else {
        error("Internal error: Missing case for ${output_format}");
    }
    if ($lint_exit && (%unknown_hooks or @{$unloadables})) {
        exit(EXIT_CODE_LINT_ISSUES_FOUND);
    }
    exit(0);
}

sub detect_hook_targets {
    if (@ARGV) {
        error("$COMMAND: No arguments supported (please remove everything after the command)");
    }
    _assert_debian_control_exists();
    _allow_unsafe_execution();
    my $explicit_targets = _load_hook_targets();
    my (%result, @targets, @unverifiable_commands, %seen_cmds);
    while (my ($target, $rule_details) = each(%{$explicit_targets})) {
        next if $target !~ m{^(?:execute_before_|execute_after_|override_)(\S+?)(-indep|-arch)?$};
        my ($command, $archness) = ($1, $2);
        my $param;
        if ($archness) {
            $param = ($archness eq '-arch') ? '-a' : '-i' ;
        }
        my ($non_empty, $filename) = @{$rule_details};

        my $target_info = {
            'target-name'           => $target,
            'command'               => $command,
            'package-section-param' => $param,
            'is-empty'              => $non_empty ? JSON::PP::false : JSON::PP::true,
            'filename'              => $filename,
        };
        push(@targets, $target_info);
        push(@unverifiable_commands, $command) if not exists($seen_cmds{$command}) and not _in_path($command);
        $seen_cmds{$command} = 1;
    }
    $result{'hook-targets'} = \@targets;
    $result{'commands-not-in-path'} = \@unverifiable_commands;
    _output(\%result);
}

sub dh_assistant_restore_file_on_clean {
    init(inhibit_log => 1);
    if (not @ARGV) {
        error("At least one file name is required");
    }
    for my $file (@ARGV) {
        lstat($file);
        if ( ! -f _ ) {
            error("The path ${file} was a symlink. It must be a file; not a symlink to a file") if -l _;
            error("The path ${file} does not exist") if not -e _;
            error("The path ${file} was not a file and this command only supports files");
        }
        if ($file =~ m{[.][.]}) {
            # Someone can provide a patch when there is a use-case for "..foo".
            # Said patch will need to ensure the file is inside the package root dir.
            error("Files containing \"..\" (which ${file} does) are not supported.");
        }
        if ($file =~ m{^/}) {
            error("Files must be relative to the package root (which ${file} was not)")
        }
        if ($file =~ m{^\.} or $file =~ m{/CVS/} or $file =~ m{/\.}) {
            error("Cowardly refusing to track hidden files / version control files (${file}).");
        }
        Debian::Debhelper::Dh_Lib::restore_file_on_clean($file)
    }
}

sub log_installed_files_cmd {
    my $on_behalf_of = 'manually-via-dh_assistant';
    init(
        options => {
            'on-behalf-of-cmd=s' => \$on_behalf_of,
        },
        inhibit_log => 1,
    );
    if (index($on_behalf_of, '/') >= 0) {
        error('The value for --on-behalf-of-cmd must not contain slashes');
    }
    if (@{$dh{DOPACKAGES}} != 1) {
        error('The log-installed-files command must act on exactly one package (use -p<pkg> to define which)');
    }
    my $package = $dh{DOPACKAGES}[0];
    for my $arg (@ARGV) {
        $arg =~ tr:/:/:s;
        if (! -e $arg) {
            warning("The path ${arg} does not exist - double check it is correct. Note: it will recorded anyway.");
        }
    }
    log_installed_files({
        'package'   => $package,
        'tool_name' => $on_behalf_of,
    }, @ARGV);
}

sub supports {
    my ($command, @more) = @ARGV;
    if (@more or not defined($command)) {
        error("$COMMAND: Please provide exactly one argument");
    }
    exit(0) if exists($COMMANDS{$command});
    exit(2);
}

if (not defined($COMMAND)) {
    error('Usage: ' . basename($0) . ' <command>');
}
my $handler = $COMMANDS{$COMMAND};
if (not defined($handler)) {
    warning("Arguments/options must not be the first argument (except for --help)")
        if $COMMAND =~ m/^-/;
    my $available_cmds = join(' ', sort(grep { $_ ne '-h' and $_ ne '--help' and $_ ne 'help' } keys(%COMMANDS)));
    error("Unknown command: $COMMAND. Use \"help\" or \"--help\" as first argument for usage. Available commands: ${available_cmds}");
}

$handler->();

=head1 SEE ALSO

L<debhelper(7)>

This program is a part of debhelper.

=cut

1;