From 71804e56eb3612eabc51887fe4d46961684a3ecc Mon Sep 17 00:00:00 2001
From: Xavier Claessens <xavier.claessens@collabora.com>
Date: Mon, 13 Apr 2020 18:12:43 -0400
Subject: [PATCH] wrap: Add special 'dependency_names' key in [provide] section

The value for that key must be a coma separated list of dependecy names
provided by that subproject, when no variable name is needed because the
subproject uses override_dependency().
---
 .../markdown/Wrap-dependency-system-manual.md | 22 +++++++++++++++----
 mesonbuild/wrap/wrap.py                       | 14 +++++++++++-
 .../common/102 subproject subdir/meson.build  |  2 +-
 .../subprojects/sub_implicit.wrap             |  4 ++--
 4 files changed, 34 insertions(+), 8 deletions(-)

diff --git a/docs/markdown/Wrap-dependency-system-manual.md b/docs/markdown/Wrap-dependency-system-manual.md
index cb7c6d6a0..b9279448c 100644
--- a/docs/markdown/Wrap-dependency-system-manual.md
+++ b/docs/markdown/Wrap-dependency-system-manual.md
@@ -145,12 +145,15 @@ wrap-git, the repository must contain all Meson build definitions.
 Wrap files can define the dependencies it provides in the `[provide]` section.
 When a wrap file provides the dependency `foo` any call do `dependency('foo')`
 will automatically fallback to that subproject even if no `fallback` keyword
-argument is given. Each entry in the format `dependency_name = variable_name`,
+argument is given. It is recommended for subprojects to call
+`meson.override_dependency('foo', foo_dep)`, dependency name can then be added into
+the special `dependency_names` entry which takes coma separated list of dependency
+names. For backward compatibility with subprojects that does not call
+`meson.override_dependency()`, the variable name can be provided in the wrap file
+with entries in the format `dependency_name = variable_name`,
 where `dependency_name` usually match the corresponding pkg-config name and
 `variable_name` is the name of a variable defined in the subproject that should
-be returned for that dependency. In the case the subproject uses
-`meson.override_dependency('foo', foo_dep)` the `variable_name` can be left empty
-in the wrap file.
+be returned for that dependency.
 
 For example `glib.wrap` provides `glib-2.0`, `gobject-2.0` and `gio-2.0`. A wrap
 file for glib would look like:
@@ -165,6 +168,17 @@ gobject-2.0=gobject_dep
 gio-2.0=gio_dep
 ```
 
+Alternatively, when using a recent enough version of glib that uses
+`meson.override_dependency()`:
+```ini
+[wrap-git]
+url=https://gitlab.gnome.org/GNOME/glib.git
+revision=glib-2-62
+
+[provide]
+dependency_names = glib-2.0, gobject-2.0, gio-2.0
+```
+
 With such wrap file, `dependency('glib-2.0')` will automatically fallback to use
 `glib.wrap` and return `glib_dep` variable from the subproject.
 
diff --git a/mesonbuild/wrap/wrap.py b/mesonbuild/wrap/wrap.py
index 63ee34968..d645c2cdb 100644
--- a/mesonbuild/wrap/wrap.py
+++ b/mesonbuild/wrap/wrap.py
@@ -127,7 +127,19 @@ class PackageDefinition:
     def parse_provide_section(self):
         self.provide = {self.name: None}
         if self.config.has_section('provide'):
-            self.provide.update(self.config['provide'])
+            for k, v in self.config['provide'].items():
+                if k == 'dependency_names':
+                    # A coma separated list of dependency names that does not
+                    # need a variable name
+                    names = {n.strip(): None for n in v.split(',')}
+                    self.provide.update(names)
+                    continue
+                if not v:
+                    m = ('Empty dependency variable name for {!r} in {}. '
+                         'If the subproject uses meson.override_dependency() '
+                         'it can be added in the "dependency_names" special key.')
+                    raise WrapException(m.format(k, self.basename))
+                self.provide[k] = v
 
     def get(self, key: str) -> str:
         try:
diff --git a/test cases/common/102 subproject subdir/meson.build b/test cases/common/102 subproject subdir/meson.build
index bc202a3b2..6faff753f 100644
--- a/test cases/common/102 subproject subdir/meson.build	
+++ b/test cases/common/102 subproject subdir/meson.build	
@@ -31,7 +31,7 @@ d = dependency('sub_implicit')
 assert(d.found(), 'Should implicitly fallback')
 
 # Verify that implicit fallback works because sub_implicit.wrap has
-# `sub_implicit_provide1=` and the subproject overrides sub_implicit_provide1.
+# `dependency_names=sub_implicit_provide1` and the subproject overrides sub_implicit_provide1.
 d = dependency('sub_implicit_provide1')
 assert(d.found(), 'Should implicitly fallback')
 
diff --git a/test cases/common/102 subproject subdir/subprojects/sub_implicit.wrap b/test cases/common/102 subproject subdir/subprojects/sub_implicit.wrap
index c14fff045..e668a8da3 100644
--- a/test cases/common/102 subproject subdir/subprojects/sub_implicit.wrap	
+++ b/test cases/common/102 subproject subdir/subprojects/sub_implicit.wrap	
@@ -1,5 +1,5 @@
 [wrap-file]
 
 [provide]
-sub_implicit_provide1=
-sub_implicit_provide2=sub_implicit_provide2_dep
+dependency_names = sub_implicit_provide1
+sub_implicit_provide2 = sub_implicit_provide2_dep