Make copying more predictable. (#73)

Don't make the copy operation dependent on whether the target directory
exists or not.
Making it dependent has the following drawbacks:
1. the directory could be created outside of our control.
2. It's annoying in programs to test first whether the target exists.
3. There isn't a good way to copy the content of the source to the
target if it already exists.

Author: floitsch

src/file.toit

@@ -336,16 +336,18 @@ Reads the destination of the link $name
 readlink name/string -> string:
   #primitive.file.readlink
 
-/** Windows specific attribute for read-only files */
-WINDOWS-FILE-ATTRIBUTE-READONLY ::= 0x01
-/** Windows specific attribute for hidden files */
-WINDOWS-FILE-ATTRIBUTE-HIDDEN   ::= 0x02
-/** Windows specific attribute for system files */
-WINDOWS-FILE-ATTRIBUTE-SYSTEM   ::= 0x04
-/** Windows specific attribute for normal files */
-WINDOWS-FILE-ATTRIBUTE-NORMAL   ::= 0x80
-/** Windows specific attribute for archive files */
-WINDOWS-FILE-ATTRIBUTE-ARCHIVE  ::= 0x20
+/** Windows specific attribute for read-only files. */
+WINDOWS-FILE-ATTRIBUTE-READONLY  ::= 0x01
+/** Windows specific attribute for hidden files. */
+WINDOWS-FILE-ATTRIBUTE-HIDDEN    ::= 0x02
+/** Windows specific attribute for system files. */
+WINDOWS-FILE-ATTRIBUTE-SYSTEM    ::= 0x04
+/** Windows specific attribute for sub directories. */
+WINDOWS-FILE-ATTRIBUTE-DIRECTORY ::= 0x10
+/** Windows specific attribute for archive files. */
+WINDOWS-FILE-ATTRIBUTE-ARCHIVE   ::= 0x20
+/** Windows specific attribute for normal files. */
+WINDOWS-FILE-ATTRIBUTE-NORMAL    ::= 0x80
 
 /**
 Changes filesystem permissions for the file $name to $permissions.
@@ -356,10 +358,13 @@ chmod name/string permissions/int:
 /**
 Copies $source to $target.
 
-If $target is a directory, then takes the basename of $source and appends it to
-  $target.
+If $source is a file, then $target contains the copy and permissions of $source after
+  the call.
+If $source is a directory and $recursive is true, then $target contains the copy of
+  the content of $source after the call. That is, all files that exist in $source
+  will exist in $target after the call. The $target directory may exist.
 
-The location for $target must exist. That is, when copying to `foo/bar`, `foo`
+The location (dirname) of $target must exist. That is, when copying to `foo/bar`, `foo`
   must exist.
 
 If $dereference is true, then symbolic links are followed.
@@ -370,10 +375,14 @@ If $recursive is true, then directories are copied recursively. If $recursive is
 copy --source/string --target/string --dereference/bool=false --recursive/bool=false -> none:
   // A queue for pending recursive copies.
   queue := Deque
-  if is-directory target:
-    target = "$target/$(basename_ source)"
 
-  copy_ --source=source --target=target --dereference=dereference --recursive=recursive --queue=queue
+  copy_
+      --source=source
+      --target=target
+      --dereference=dereference
+      --recursive=recursive
+      --queue=queue
+      --allow-existing-target-directory
   while not queue.is-empty:
     next := queue.remove-first
     new-source := next[0]
@@ -405,33 +414,45 @@ copy --source/string --target/string --dereference/bool=false --recursive/bool=f
             --dereference=dereference
             --recursive=recursive
             --queue=queue
+            --no-allow-existing-target-directory
     finally:
       directory-stream.close
       if target-permissions != -1:
         // Make the directory read-only again.
         chmod new-target target-permissions
 
+SPECIAL-WINDOWS-PERMISSIONS_ ::= WINDOWS-FILE-ATTRIBUTE-READONLY | WINDOWS-FILE-ATTRIBUTE-HIDDEN
+
 /**
 Copies $source to $target.
 
 The given $queue is filled with pending recursive copies. Each entry in the $queue
   is a pair of source, target, where both are directories that exist.
 */
-copy_ --source/string --target/string --dereference/bool --recursive/bool --queue/Deque -> none:
+copy_ -> none
+    --source/string
+    --target/string
+    --dereference/bool
+    --recursive/bool
+    --queue/Deque
+    --allow-existing-target-directory/bool:
+  is-windows := system.platform == system.PLATFORM-WINDOWS
+
   source-stat := stat source --follow-links=dereference
   if not source-stat:
     throw "File/directory $source not found"
+  source-permissions := source-stat[ST-MODE]
+  type := source-stat[ST-TYPE]
   target-stat := stat target
-  if target-stat:
+  if target-stat and (type != DIRECTORY or not allow-existing-target-directory):
     throw "'$target' already exists"
 
-  type := source-stat[ST-TYPE]
   if type == SYMBOLIC-LINK or type == DIRECTORY-SYMBOLIC-LINK:
     // When taking the stat of the source we already declared whether we
     // dereference the link or not. If we are here, then we do not dereference
     // and should thus copy the link.
     link-target := readlink source
-    if system.platform == system.PLATFORM-WINDOWS:
+    if is-windows:
       // Work around https://github.com/toitlang/toit/issues/2090, where reading
       // an absolute symlink starts with '\??\' which Toit can't deal with if
       // written as value of a link.
@@ -445,19 +466,29 @@ copy_ --source/string --target/string --dereference/bool --recursive/bool --queu
   if type == DIRECTORY:
     if not recursive:
       throw "Cannot copy directory '$source' without --recursive"
-    mkdir target source-stat[ST-MODE]
+    if not target-stat:
+      mkdir target source-permissions
+      if is-windows and source-permissions & SPECIAL-WINDOWS-PERMISSIONS_ != 0:
+        // The Windows file attributes are not taken into account when creating a new directory.
+        // Apply them now.
+        chmod target source-permissions
+
     queue.add [source, target]
     return
 
   in-stream := Stream.for-read source
-  out-stream := Stream.for-write target --permissions=source-stat[ST-MODE]
+  out-stream := Stream.for-write target --permissions=source-permissions
   out-writer := Writer out-stream
   try:
     while data := in-stream.read:
       out-writer.write data
   finally:
     in-stream.close
     out-writer.close
+  if is-windows and (source-permissions & SPECIAL-WINDOWS-PERMISSIONS_) != 0:
+    // The Windows file attributes are not taken into account when creating a new file.
+    // Apply them now.
+    chmod target source-permissions
 
 /**
 Returns the directory part of the given $path.

tests/copy_test.toit

@@ -16,8 +16,8 @@ with-tmp-dir [block]:
     directory.rmdir --force --recursive tmp-dir
 
 main:
-  // test-recursive
-  // test-permissions
+  test-recursive
+  test-permissions
   test-symlinks
 
 test-recursive:
@@ -34,16 +34,9 @@ test-recursive:
     file.copy --source=tmp-file --target=file2
     expect-equals content (file.read-content file2)
 
-    // Copy of absolute path to absolute directory path.
-    subdir := "$tmp-dir/subdir"
-    directory.mkdir subdir
-    sub-file := "$subdir/file.txt"
-    file.copy --source=tmp-file --target=subdir
-    expect-equals content (file.read-content sub-file)
-
     // Copy of relative file to relative directory path.
     directory.mkdir "subdir2"
-    file.copy --source="file.txt" --target="subdir2"
+    file.copy --source="file.txt" --target="subdir2/file.txt"
     expect-equals content (file.read-content "subdir2/file.txt")
     expect-equals content (file.read-content "$tmp-dir/subdir2/file.txt")
 
@@ -54,16 +47,24 @@ test-recursive:
     expect-equals content (file.read-content "subdir3/file.txt")
     expect-equals other-content (file.read-content "subdir3/nested-subdir/other.txt")
 
+    // Copy recursive to existing directory.
+    directory.mkdir "subdir4"
+    file.copy --source="subdir3" --target="subdir4" --recursive
+    expect-equals content (file.read-content "subdir4/file.txt")
+    expect-equals other-content (file.read-content "subdir4/nested-subdir/other.txt")
+
 test-permissions:
   file-permission0/int := ?
   file-permission1/int := ?
   dir-permission/int := ?
   read-only-dir-permission/int := ?
   if platform == PLATFORM-WINDOWS:
-    file-permission0 = file.WINDOWS-FILE-ATTRIBUTE-HIDDEN | file.WINDOWS-FILE-ATTRIBUTE-NORMAL
-    file-permission1 = file.WINDOWS-FILE-ATTRIBUTE-READONLY | file.WINDOWS-FILE-ATTRIBUTE-NORMAL
-    dir-permission = 0
-    read-only-dir-permission = file.WINDOWS-FILE-ATTRIBUTE-READONLY
+    // We use the "archive" attribute, since we modify the files, and this is the default
+    // attribute for modified files. The idea is that the backup software clears this bit.
+    file-permission0 = file.WINDOWS-FILE-ATTRIBUTE-HIDDEN | file.WINDOWS-FILE-ATTRIBUTE-ARCHIVE
+    file-permission1 = file.WINDOWS-FILE-ATTRIBUTE-READONLY | file.WINDOWS-FILE-ATTRIBUTE-ARCHIVE
+    dir-permission = file.WINDOWS-FILE-ATTRIBUTE-DIRECTORY
+    read-only-dir-permission = file.WINDOWS-FILE-ATTRIBUTE-READONLY | file.WINDOWS-FILE-ATTRIBUTE-DIRECTORY
   else:
     file-permission0 = 0b111_000_000
     file-permission1 = 0b100_000_000