sourceset: add all_dependencies() method

'if_true' sources should be built with their dependencies, as
illustrated by test case change.

Ideally, I think we would want only the files with the dependencies to
be built with the flags, but that would probably change the way
sourceset are used.

docs/markdown/SourceSet-module.md

@@ -149,6 +149,17 @@ sources are included (if any).
 
 **Returns**: a list of file objects
 
+#### `all_dependencies()` *(since 0.52.0)*
+
+``` meson
+list source_set.all_dependencies(...)
+```
+
+Returns a list of all dependencies that were placed in the source set
+using `add` (including nested source sets) and that were found.
+
+**Returns**: a list of dependencies
+
 #### `apply()`
 
 ``` meson

docs/markdown/snippets/source_set_enhancements.md

@@ -0,0 +1,4 @@
+## Enhancements to the source_set module
+
+`SourceSet` objects now provide the `all_dependencies()` method, that
+complement the existing `all_sources()` method.

mesonbuild/modules/sourceset.py

@@ -41,6 +41,7 @@ class SourceSetHolder(MutableInterpreterObject, ObjectHolder):
             'add': self.add_method,
             'add_all': self.add_all_method,
             'all_sources': self.all_sources_method,
+            'all_dependencies': self.all_dependencies_method,
             'apply': self.apply_method,
         })
 
@@ -131,6 +132,14 @@ class SourceSetHolder(MutableInterpreterObject, ObjectHolder):
         files = self.collect(lambda x: True, True)
         return list(files.sources)
 
+    @noKwargs
+    @noPosargs
+    @FeatureNew('source_set.all_dependencies() method', '0.52.0')
+    def all_dependencies_method(self, args, kwargs):
+        self.frozen = True
+        files = self.collect(lambda x: True, True)
+        return list(files.dependencies)
+
     @permittedKwargs(['strict'])
     def apply_method(self, args, kwargs):
         if len(args) != 1:

test cases/common/222 source set realistic example/meson.build

@@ -11,14 +11,15 @@ endif
 ss = import('sourceset')
 kconfig = import('unstable-kconfig')
 
-zlib = dependency('zlib', version : '>=1.2.8', required: false)
+zlib = declare_dependency(compile_args: '-DZLIB=1')
+another = declare_dependency(compile_args: '-DANOTHER=1')
 not_found = dependency('not-found', required: false)
 
 common = ss.source_set()
 specific = ss.source_set()
 
 common.add(files('main.cc'))
-common.add(when: zlib, if_true: files('zlib.cc'))
+common.add(when: [zlib, another], if_true: files('zlib.cc'))
 common.add(when: not_found,
            if_true: files('was-found.cc'),
            if_false: files('not-found.cc'))
@@ -31,7 +32,8 @@ if meson.is_unity()
   common = ss.source_set()
 endif
 
-common_lib = static_library('common', common.all_sources())
+common_lib = static_library('common', common.all_sources(),
+                            dependencies: common.all_dependencies())
 
 targets = [ 'arm', 'aarch64', 'x86' ]
 target_dirs = { 'arm' : 'arm', 'aarch64' : 'arm', 'x86': 'x86' }

test cases/common/222 source set realistic example/zlib.cc

@@ -6,8 +6,10 @@ struct ZLibDependency : Dependency {
 };
 
 void ZLibDependency::initialize() {
-    std::cout << ANSI_START << "hello from zlib"
-              << ANSI_END << std::endl;
+    if (ZLIB && ANOTHER) {
+        std::cout << ANSI_START << "hello from zlib"
+                  << ANSI_END << std::endl;
+    }
 }
 
 ZLibDependency zlib;