[mm-common] meson.build: Make it possible to use mm-common as a subproject

[Kjell Ahlstedt <kjellahl src gnome org>]

commit 5461f51e1f2e8ba55615c233ca41efa16da04005
Author: Kjell Ahlstedt <kjellahlstedt gmail com>
Date:   Fri Mar 12 16:29:01 2021 +0100

    meson.build: Make it possible to use mm-common as a subproject
    
    If mm-common is a subproject, make mm-common-get2 that can be executed
    without being installed. The main project is built before the subprojects
    have been installed.

 Makefile.am                  |  1 +
 meson.build                  | 47 +++++++++++++++++++++++++++++++++++++++++++-
 util/meson_aux/copy-files.py | 33 +++++++++++++++++++++++++++++++
 3 files changed, 80 insertions(+), 1 deletion(-)
---
diff --git a/Makefile.am b/Makefile.am
index 3d8762e..c7511bd 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -130,6 +130,7 @@ MAINTAINERCLEANFILES = $(dist_doctags_DATA)
 EXTRA_DIST = \
   meson.build \
   meson_options.txt \
+  util/meson_aux/copy-files.py \
   util/meson_aux/extra-dist-cmd.py \
   util/meson_aux/extra-install-cmd.py \
   util/meson_aux/libstdcxx-tag.py \
diff --git a/meson.build b/meson.build
index b89ea25..3f91718 100644
--- a/meson.build
+++ b/meson.build
@@ -2,7 +2,7 @@
 
 project('mm-common',
   version: '1.0.2',
-  meson_version: '>= 0.50.0', # required for python3.path()
+  meson_version: '>= 0.54.0', # required for meson.override_dependency()
   license: 'GPLv2+'
 )
 
@@ -205,6 +205,51 @@ configure_file(
   install_dir: install_man1dir
 )
 
+if meson.is_subproject()
+  # A version of mm-common-get that can be executed uninstalled.
+  conf_data_subproj = configuration_data()
+  conf_data_subproj.merge_from(conf_data)
+  conf_data_subproj.set('configure_input', 'mm-common-get2 (for execution uninstalled).  Generated from 
util/mm-common-get.in')
+  conf_data_subproj.set('datadir_py', project_build_root)
+  mm_common_get2 = configure_file(
+    input: 'util' / 'mm-common-get.in',
+    output: 'mm-common-get2',
+    configuration: conf_data_subproj,
+    install: false,
+  )
+  # Make the uninstalled mm-common-get2 executable.
+  cmd_py = '''
+import os
+import sys
+os.chmod(sys.argv[1], 0o755)'''
+  run_command(python3, '-c', cmd_py, project_build_root / 'mm-common-get2')
+
+  # A main project that looks for mm-common-get shall find mm_common_get2.
+  meson.override_find_program('mm-common-get', mm_common_get2)
+
+  # Copy files needed by mm-common-get2 from source dir to build dir.
+  # The directory structure must be the same as in the installation directory.
+  run_command(python3, script_dir / 'copy-files.py',
+    project_source_root / 'util' / 'build_scripts',
+    project_build_root / meson.project_name() / 'build',
+    meson_build_support_basefiles,
+  )
+  run_command(python3, script_dir / 'copy-files.py',
+    project_source_root / 'util',
+    project_build_root / meson.project_name() / 'doctool',
+    doctool_basefiles,
+  )
+
+  mm_common_libstdc_dep = declare_dependency(
+    variables: {
+      'doxytagfile': project_build_root / 'libstdc++.tag',
+      'htmlrefpub': 'http://gcc.gnu.org/onlinedocs/libstdc++/latest-doxygen/'
+    }
+  )
+  # A main project that looks for mm-common-libstdc++.pc shall find mm_common_libstdc_dep.
+  meson.override_dependency('mm-common-libstdc++', mm_common_libstdc_dep)
+endif
+
 # Skeleton project.
 skeletonmm_basefiles = [
   '.gitignore',
diff --git a/util/meson_aux/copy-files.py b/util/meson_aux/copy-files.py
new file mode 100755
index 0000000..b6963e2
--- /dev/null
+++ b/util/meson_aux/copy-files.py
@@ -0,0 +1,33 @@
+#!/usr/bin/env python3
+
+# External command, intended to be called with run_command() in meson.build.
+
+#                argv[1]    argv[2]    argv[3:]
+# copy-files.py <from_dir> <to_dir> <file_names>...
+
+import os
+import sys
+import shutil
+
+# <from_dir> is an absolute or relative path of the directory to copy from.
+# <to_dir> is an absolute or relative path of the directory to copy to.
+from_dir_root = sys.argv[1]
+to_dir_root = sys.argv[2]
+
+# Copy some files if they exist in from_dir, but not in the destination
+# directory, or if they are not up to date in the destination directory.
+# (The term "source directory" is avoided here, because from_dir might not
+# be what Meson calls a source directory as opposed to a build directory.)
+
+for file in sys.argv[3:]:
+  from_file = os.path.join(from_dir_root, file)
+  to_file = os.path.join(to_dir_root, file)
+  if os.path.isfile(from_file) and ((not os.path.isfile(to_file))
+     or (os.stat(from_file).st_mtime > os.stat(to_file).st_mtime)):
+
+    # Create the destination directory, if it does not exist.
+    os.makedirs(os.path.dirname(to_file), exist_ok=True)
+
+    # shutil.copy2() copies timestamps and some other file metadata.
+    shutil.copy2(from_file, to_file)
+sys.exit(0)