Allow add_dist_script() in subprojects

Fixes: #8440.

docs/markdown/Reference-manual.md

@@ -1907,16 +1907,25 @@ the following methods.
   archived. Note that this runs the script file that is in the
   _staging_ directory, not the one in the source directory. If the
   script file can not be found in the staging directory, it is a hard
-  error. This command can only invoked from the main project, calling
-  it from a subproject is a hard error. *(since 0.49.0)* Accepts multiple arguments
-  for the script. *(since 0.54.0)* The `MESON_SOURCE_ROOT` and `MESON_BUILD_ROOT`
-  environment variables are set when dist scripts are run.
-
+  error. The `MESON_DIST_ROOT` environment variables is set when dist scripts is
+  run.
+  *(since 0.49.0)* Accepts multiple arguments for the script.
+  *(since 0.54.0)* The `MESON_SOURCE_ROOT` and `MESON_BUILD_ROOT`
+  environment variables are set when dist scripts are run. They are path to the
+  root source and build directory of the main project, even when the script
+  comes from a subproject.
   *(since 0.55.0)* The output of `configure_file`, `files`, and `find_program`
   as well as strings.
-
   *(since 0.57.0)* `file` objects and the output of `configure_file` may be
   used as the `script_name` parameter.
+  *(since 0.58.0)* This command can be invoked from a subproject, it was a hard
+  error in earlier versions. Subproject dist scripts will only be executed
+  when running `meson dist --include-subprojects`. `MESON_PROJECT_SOURCE_ROOT`,
+  `MESON_PROJECT_BUILD_ROOT` and `MESON_PROJECT_DIST_ROOT` environment
+  variables are set when dist scripts are run. They are identical to
+  `MESON_SOURCE_ROOT`, `MESON_BUILD_ROOT` and `MESON_DIST_ROOT` for main project
+  scripts, but for subproject scripts they have the path to the root of the
+  subproject appended, usually `subprojects/<subproject-name>`.
 
 - `add_install_script(script_name, arg1, arg2, ...)`: causes the script
   given as an argument to be run during the install step, this script

docs/markdown/snippets/dist_script.md

@@ -0,0 +1,14 @@
+## `meson.add_dist_script()` allowd in subprojects
+
+`meson.add_dist_script()` can now be invoked from a subproject, it was a hard
+error in earlier versions. Subproject dist scripts will only be executed
+when running `meson dist --include-subprojects`. `MESON_PROJECT_SOURCE_ROOT`,
+`MESON_PROJECT_BUILD_ROOT` and `MESON_PROJECT_DIST_ROOT` environment variables
+are set when dist scripts are run. They are identical to `MESON_SOURCE_ROOT`,
+`MESON_BUILD_ROOT` and `MESON_DIST_ROOT` for main project scripts, but for
+subproject scripts they have the path to the root of the subproject appended,
+usually `subprojects/<subproject-name>`.
+
+Note that existing dist scripts likely need to be modified to use those new
+environment variables instead of `MESON_DIST_ROOT` to work properly when used
+from a subproject.

mesonbuild/interpreter.py

@@ -2028,7 +2028,8 @@ class MesonMain(InterpreterObject):
             FeatureNew.single_use('Passing file object to script parameter of add_dist_script',
                                   '0.57.0', self.interpreter.subproject)
         if self.interpreter.subproject != '':
-            raise InterpreterException('add_dist_script may not be used in a subproject.')
+            FeatureNew.single_use('Calling "add_dist_script" in a subproject',
+                                  '0.58.0', self.interpreter.subproject)
         script_args = self._process_script_args('add_dist_script', args[1:], allow_built=True)
         script = self._find_source_script(args[0], script_args)
         self.build.dist_scripts.append(script)

mesonbuild/mdist.py

@@ -78,13 +78,19 @@ def process_submodules(dirname):
         del_gitfiles(os.path.join(dirname, v))
 
 
-def run_dist_scripts(src_root, bld_root, dist_root, dist_scripts):
+def run_dist_scripts(src_root, bld_root, dist_root, dist_scripts, subprojects):
     assert(os.path.isabs(dist_root))
     env = {}
     env['MESON_DIST_ROOT'] = dist_root
     env['MESON_SOURCE_ROOT'] = src_root
     env['MESON_BUILD_ROOT'] = bld_root
     for d in dist_scripts:
+        if d.subproject and d.subproject not in subprojects:
+            continue
+        subdir = subprojects.get(d.subproject, '')
+        env['MESON_PROJECT_DIST_ROOT'] = os.path.join(dist_root, subdir)
+        env['MESON_PROJECT_SOURCE_ROOT'] = os.path.join(src_root, subdir)
+        env['MESON_PROJECT_BUILD_ROOT'] = os.path.join(bld_root, subdir)
         name = ' '.join(d.cmd_args)
         print(f'Running custom dist script {name!r}')
         try:
@@ -141,7 +147,7 @@ def git_clone(src_root, distdir):
 def create_dist_git(dist_name, archives, src_root, bld_root, dist_sub, dist_scripts, subprojects):
     distdir = os.path.join(dist_sub, dist_name)
     git_clone(src_root, distdir)
-    for path in subprojects:
+    for path in subprojects.values():
         sub_src_root = os.path.join(src_root, path)
         sub_distdir = os.path.join(distdir, path)
         if os.path.exists(sub_distdir):
@@ -150,7 +156,7 @@ def create_dist_git(dist_name, archives, src_root, bld_root, dist_sub, dist_scri
             git_clone(sub_src_root, sub_distdir)
         else:
             shutil.copytree(sub_src_root, sub_distdir)
-    run_dist_scripts(src_root, bld_root, distdir, dist_scripts)
+    run_dist_scripts(src_root, bld_root, distdir, dist_scripts, subprojects)
     output_names = []
     for a in archives:
         compressed_name = distdir + archive_extension[a]
@@ -278,13 +284,13 @@ def run(options):
 
     archives = determine_archives_to_generate(options)
 
-    subprojects = []
+    subprojects = {}
     extra_meson_args = []
     if options.include_subprojects:
         subproject_dir = os.path.join(src_root, b.subproject_dir)
         for sub in b.subprojects:
             directory = wrap.get_directory(subproject_dir, sub)
-            subprojects.append(os.path.join(b.subproject_dir, directory))
+            subprojects[sub] = os.path.join(b.subproject_dir, directory)
         extra_meson_args.append('-Dwrap_mode=nodownload')
 
     if is_git(src_root):

run_unittests.py

@@ -3189,6 +3189,10 @@ class AllPlatformTests(BasePlatformTests):
                 _git_init(project_dir)
                 self.init(project_dir)
                 self.build('dist')
+
+                self.new_builddir()
+                self.init(project_dir, extra_args=['-Dsub:broken_dist_script=false'])
+                self._run(self.meson_command + ['dist', '--include-subprojects'], workdir=self.builddir)
         except PermissionError:
             # When run under Windows CI, something (virus scanner?)
             # holds on to the git files so cleaning up the dir

test cases/unit/35 dist script/meson.build

@@ -6,3 +6,5 @@ test('compare', exe)
 
 meson.add_dist_script('replacer.py', '"incorrect"', '"correct"')
 meson.add_dist_script(find_program('replacer.py'), '"incorrect"', '"correct"')
+
+subproject('sub')

test cases/unit/35 dist script/subprojects/sub/dist-script.py

@@ -0,0 +1,12 @@
+#!/usr/bin/env python3
+
+import os
+import pathlib
+import sys
+
+assert sys.argv[1] == 'success'
+
+source_root = pathlib.Path(os.environ['MESON_PROJECT_DIST_ROOT'])
+modfile = source_root / 'prog.c'
+with modfile.open('w') as f:
+    f.write('int main(){return 0;}')

test cases/unit/35 dist script/subprojects/sub/meson.build

@@ -0,0 +1,11 @@
+project('sub')
+
+if get_option('broken_dist_script')
+  # Make sure we can add a dist script in a subproject, but it won't be run
+  # if not using --include-subprojects.
+  meson.add_dist_script('dist-script.py', 'broken')
+else
+  # The dist script replace prog.c with something that actually build.
+  meson.add_dist_script('dist-script.py', 'success')
+  executable('prog', 'prog.c')
+endif

test cases/unit/35 dist script/subprojects/sub/meson_options.txt

@@ -0,0 +1 @@
+option('broken_dist_script', type: 'boolean', value: true)

test cases/unit/35 dist script/subprojects/sub/prog.c

@@ -0,0 +1 @@
+#error This should be replaced by a program during dist