Merge pull request #14 from tweag/ch/reduce_sh_posix_toolchain_attr_number

sh_posix_toolchain: reduce number of attributes by using attr.string_dict instead of attr.string list

Author: smelc

CHANGELOG.md

@@ -8,6 +8,30 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/).
 
 [Unreleased]: https://github.com/tweag/rules_sh/compare/v0.1.1...HEAD
 
+### Changed
+
+- `sh_posix_toolchain` now has a single attribute `cmds`, which
+  is a string to string `dict`; instead of having one attribute
+  per member of `posix.commands`. It is a breaking change if you were
+  calling `sh_posix_toolchain` directly.
+
+  If you were calling this rule as follows:
+
+  ```
+  sh_posix_toolchain(cat = "/bin/cat", wc = "/usr/bin/wc")
+  ```
+
+  you should now do:
+
+  ```
+  sh_posix_toolchain(cmds = { "cat": "/bin/cat", "wc": "/usr/bin/wc" })
+  ```
+
+  See PR [#14][#14] and issue [#13][#13] for the motivation.
+
+[#14]: https://github.com/tweag/rules_sh/pull/14
+[#13]: https://github.com/tweag/rules_sh/issues/13
+
 ## [0.1.1] - 2019-11-13
 
 [0.1.1]: https://github.com/tweag/rules_sh/compare/v0.1.0...v0.1.1

sh/posix.bzl

@@ -181,11 +181,15 @@ MAKE_VARIABLES = "@rules_sh//sh/posix:make_variables"
 
 def _sh_posix_toolchain_impl(ctx):
     commands = {}
+    cmds = ctx.attr.cmds
     for cmd in _commands:
-        cmd_path = getattr(ctx.attr, cmd, None)
+        cmd_path = cmds.get(cmd, None)
         if not cmd_path:
             cmd_path = None
         commands[cmd] = cmd_path
+    unrecognizeds = [cmd for cmd in cmds.keys() if cmd not in _commands]
+    if unrecognizeds:
+        fail("Unrecognized commands in keys of sh_posix_toolchain's \"cmds\" attributes: {}. See posix.commands in @rules_sh//sh:posix.bzl for the list of recognized commands.".format(", ".join(unrecognizeds)))
     cmd_paths = {
         paths.dirname(cmd_path): None
         for cmd_path in commands.values()
@@ -198,11 +202,10 @@ def _sh_posix_toolchain_impl(ctx):
 
 sh_posix_toolchain = rule(
     attrs = {
-        cmd: attr.string(
-            doc = "Absolute path to the {} command.".format(cmd),
-            mandatory = False,
+        "cmds": attr.string_dict(
+            doc = "dict where keys are command names and values are paths",
+            mandatory = True,
         )
-        for cmd in _commands
     },
     doc = """
 A toolchain capturing standard Unix shell commands.
@@ -300,7 +303,9 @@ load("@rules_sh//sh:posix.bzl", "sh_posix_toolchain")
 sh_posix_toolchain(
     name = "local_posix",
     visibility = ["//visibility:public"],
-    {commands}
+    cmds = {{
+        {commands}
+    }}
 )
 toolchain(
     name = "local_posix_toolchain",
@@ -316,8 +321,8 @@ toolchain(
     ],
 )
 """.format(
-        commands = ",\n    ".join([
-            '{cmd} = "{path}"'.format(cmd = cmd, path = cmd_path)
+        commands = ",\n        ".join([
+            '"{cmd}": "{path}"'.format(cmd = cmd, path = cmd_path)
             for (cmd, cmd_path) in commands.items()
             if cmd_path
         ]),