From 95fb6ef29ca44ff1fbeb4bf340a19004d3f6ba3d Mon Sep 17 00:00:00 2001
From: Kjell Ahlstedt <kjellahlstedt@gmail.com>
Date: Tue, 18 May 2021 09:45:15 +0200
Subject: Add dependencies to Doxygen tag files in subprojects

Doxygen in a main project shall not be called before tag files have been
created or updated in subprojects.
---
 docs/reference/meson.build | 17 ++++++++++++++---
 meson.build                |  2 ++
 2 files changed, 16 insertions(+), 3 deletions(-)

diff --git a/docs/reference/meson.build b/docs/reference/meson.build
index ca7ab2a..59d41e8 100644
--- a/docs/reference/meson.build
+++ b/docs/reference/meson.build
@@ -4,19 +4,27 @@
 #        sigcxx_api_version, build_documentation, source_h_files,
 #        built_h_files, install_datadir, python3, doc_reference,
 #        built_h_file_targets, can_add_dist_script
-# Output: install_docdir, install_devhelpdir, tag_file
 # Output: install_docdir, install_devhelpdir, if build_documentation: tag_file
 
 tag_file_modules = [
   'mm-common-libstdc++',
 ]
 doxygen_tagfiles = ''
+doxygen_tag_targets = []
 docinstall_flags = []
 foreach module : tag_file_modules
   depmod = dependency(module, required: false)
   if depmod.found()
     doxytagfile = depmod.get_variable(pkgconfig: 'doxytagfile', internal: 'doxytagfile', default_value: '')
     if doxytagfile != ''
+      if depmod.type_name() == 'internal'
+        # Subprojects must build their tag files before doxygen is called.
+        if module.startswith('mm-common')
+          doxygen_tag_targets += subproject('mm-common').get_variable('global_tag_file_target')
+        else
+          doxygen_tag_targets += subproject(module).get_variable('global_tag_file_target')
+        endif
+      endif
       htmlrefpub = depmod.get_variable(pkgconfig: 'htmlrefpub', internal: 'htmlrefpub', default_value: '')
       htmlrefdir = depmod.get_variable(pkgconfig: 'htmlrefdir', internal: 'htmlrefdir', default_value: '')
       if htmlrefpub == ''
@@ -50,7 +58,7 @@ doc_conf_data.set('abs_top_srcdir', project_source_root)
 doc_conf_data.set('SIGCXX_API_VERSION', sigcxx_api_version)
 doc_conf_data.set('DOXYGEN_TAGFILES', doxygen_tagfiles)
 
-configure_file(
+doxyfile = configure_file(
   input: 'Doxyfile.in',
   output: '@BASENAME@',
   configuration: doc_conf_data,
@@ -96,8 +104,9 @@ if built_h_file_targets.length() > 0
       blt_h_files,
       '@INPUT@',
     ],
+    depend_files: doxyfile,
+    depends: built_h_file_targets + doxygen_tag_targets,
     build_by_default: build_documentation,
-    depends: built_h_file_targets,
     install: true,
     install_dir: install_reference_docdir,
   )
@@ -112,6 +121,8 @@ else
       '@OUTPUT@',
       '@INPUT@',
     ],
+    depend_files: doxyfile,
+    depends: doxygen_tag_targets,
     build_by_default: build_documentation,
     install: true,
     install_dir: install_reference_docdir,
diff --git a/meson.build b/meson.build
index da72505..ddb8148 100644
--- a/meson.build
+++ b/meson.build
@@ -256,6 +256,8 @@ if meson.is_subproject()
   }
   if build_documentation
     pkgconfig_vars += {'doxytagfile': tag_file.full_path()}
+    # May be used in a main project.
+    global_tag_file_target = tag_file
   endif
   sigcxx_dep = declare_dependency(
     dependencies: sigcxx_own_dep,
-- 
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