Merge pull request #6423 from dcbaker/declare-dependency-variables

Add ability to set and query arbitrary variables on declare_dependency objects 

8 files changed, 89 insertions, 25 deletions

diff --git a/docs/markdown/Dependencies.md b/docs/markdown/Dependencies.md
index e029a84..d21bb97 100644
--- a/docs/markdown/Dependencies.md
+++ b/docs/markdown/Dependencies.md
@@ -67,6 +67,7 @@ page](#dependencies-with-custom-lookup-functionality).
 # Arbitrary variables from dependencies that can be found multiple ways
 
 *Note* new in 0.51.0
+*new in 0.54.0, the `internal` keyword*
 
 When you need to get an arbitrary variables from a dependency that can be
 found multiple ways and you don't want to constrain the type you can use
@@ -79,13 +80,14 @@ var = foo.get_variable(cmake : 'CMAKE_VAR', pkgconfig : 'pkg-config-var', config
 ```
 
 It accepts the keywords 'cmake', 'pkgconfig', 'pkgconfig_define',
-'configtool', and 'default_value'. 'pkgconfig_define' works just like the
-'define_variable' argument to `get_pkgconfig_variable`. When this method is
-invoked the keyword corresponding to the underlying type of the dependency
-will be used to look for a variable. If that variable cannot be found or if
-the caller does not provide an argument for the type of dependency, one of
-the following will happen: If 'default_value' was provided that value will be
-returned, if 'default_value' was not provided then an error will be raised.
+'configtool', 'internal', and 'default_value'. 'pkgconfig_define' works just
+like the 'define_variable' argument to `get_pkgconfig_variable`. When this
+method is invoked the keyword corresponding to the underlying type of the
+dependency will be used to look for a variable. If that variable cannot be
+found or if the caller does not provide an argument for the type of
+dependency, one of the following will happen: If 'default_value' was provided
+that value will be returned, if 'default_value' was not provided then an
+error will be raised.
 
 # Declaring your own
 
@@ -289,16 +291,16 @@ libraries that have been compiled for single-threaded use instead.
 
 *(added 0.53.0)*
 
-Enables compiling and linking against the CUDA Toolkit. The `version` 
-and `modules` keywords may be passed to request the use of a specific 
+Enables compiling and linking against the CUDA Toolkit. The `version`
+and `modules` keywords may be passed to request the use of a specific
 CUDA Toolkit version and/or additional CUDA libraries, correspondingly:
 
 ```meson
 dep = dependency('cuda', version : '>=10', modules : ['cublas'])
 ```
 
-Note that explicitly adding this dependency is only necessary if you are 
-using CUDA Toolkit from a C/C++ file or project, or if you are utilizing 
+Note that explicitly adding this dependency is only necessary if you are
+using CUDA Toolkit from a C/C++ file or project, or if you are utilizing
 additional toolkit libraries that need to be explicitly linked to.
 
 ## CUPS
diff --git a/docs/markdown/Reference-manual.md b/docs/markdown/Reference-manual.md
index 6699d75..57fc1f7 100644
--- a/docs/markdown/Reference-manual.md
+++ b/docs/markdown/Reference-manual.md
@@ -413,6 +413,9 @@ keyword arguments.
   - `sources`, sources to add to targets (or generated header files
     that should be built before sources including them are built)
   - `version`, the version of this dependency, such as `1.2.3`
+  - `variables`, a dictionary of arbitrary strings, this is meant to be used
+    in subprojects where special variables would be provided via cmake or
+    pkg-config. Since 0.54.0
 
 ### dependency()
 
@@ -2373,14 +2376,16 @@ an external dependency with the following methods:
    - sources: any compiled or static sources the dependency has
 
  - `get_variable(cmake : str, pkgconfig : str, configtool : str,
-   default_value : str, pkgconfig_define : [str, str])` *(Added in
-   0.51.0)* A generic variable getter method, which replaces the
+   internal: str, default_value : str, pkgconfig_define : [str, str])`
+   *(Added in 0.51.0)* A generic variable getter method, which replaces the
    get_*type*_variable methods. This allows one to get the variable
    from a dependency without knowing specifically how that dependency
    was found. If default_value is set and the value cannot be gotten
    from the object then default_value is returned, if it is not set
    then an error is raised.
 
+   *New in 0.54.0, the `internal` keyword*
+
 ### `disabler` object
 
 A disabler object is an object that behaves in much the same way as
diff --git a/docs/markdown/Subprojects.md b/docs/markdown/Subprojects.md
index 91b1843..8232da9 100644
--- a/docs/markdown/Subprojects.md
+++ b/docs/markdown/Subprojects.md
@@ -55,6 +55,28 @@ should be named as `<project_name>_dep` (e.g. `gtest_dep`), and others can have
 
 There may be exceptions to these rules where common sense should be applied.
 
+### Adding variables to the dependency
+
+*New in 0.54.0*
+
+In some cases a project may define special variables via pkg-config or cmake
+that a caller needs to know about. Meson provides a `dependency.get_variable`
+method to hide what kind of dependency is provided, and this is available to
+subprojects as well. Use the `variables` keyword to add a dict of strings:
+
+```meson
+my_dep = declare_dependency(..., variables : {'var': 'value', 'number': '3'})
+```
+
+Which another project can access via:
+
+```meson
+var = my_dep.get_variable(internal : 'var', cmake : 'CMAKE_VAR')
+```
+
+The values of the dict must be strings, as pkg-config and cmake will return
+variables as strings.
+
 ### Build options in subproject
 
 All Meson features of the subproject, such as project options keep
diff --git a/mesonbuild/build.py b/mesonbuild/build.py
index 0eb930b..1db930e 100644
--- a/mesonbuild/build.py
+++ b/mesonbuild/build.py
@@ -1053,7 +1053,7 @@ This will become a hard error in a future Meson release.''')
                                                               [],
                                                               dep.get_compile_args(),
                                                               dep.get_link_args(),
-                                                              [], [], [], [])
+                                                              [], [], [], [], {})
                     self.external_deps.append(extpart)
                 # Deps of deps.
                 self.add_deps(dep.ext_deps)
diff --git a/mesonbuild/dependencies/base.py b/mesonbuild/dependencies/base.py
index 282c314..e9cf9ac 100644
--- a/mesonbuild/dependencies/base.py
+++ b/mesonbuild/dependencies/base.py
@@ -223,7 +223,8 @@ class Dependency:
         self.ext_deps.append(dep_type(env, kwargs))
 
     def get_variable(self, *, cmake: T.Optional[str] = None, pkgconfig: T.Optional[str] = None,
-                     configtool: T.Optional[str] = None, default_value: T.Optional[str] = None,
+                     configtool: T.Optional[str] = None, internal: T.Optional[str] = None,
+                     default_value: T.Optional[str] = None,
                      pkgconfig_define: T.Optional[T.List[str]] = None) -> T.Union[str, T.List[str]]:
         if default_value is not None:
             return default_value
@@ -235,7 +236,8 @@ class Dependency:
         return new_dep
 
 class InternalDependency(Dependency):
-    def __init__(self, version, incdirs, compile_args, link_args, libraries, whole_libraries, sources, ext_deps):
+    def __init__(self, version, incdirs, compile_args, link_args, libraries,
+                 whole_libraries, sources, ext_deps, variables: T.Dict[str, T.Any]):
         super().__init__('internal', {})
         self.version = version
         self.is_found = True
@@ -246,6 +248,7 @@ class InternalDependency(Dependency):
         self.whole_libraries = whole_libraries
         self.sources = sources
         self.ext_deps = ext_deps
+        self.variables = variables
 
     def get_pkgconfig_variable(self, variable_name, kwargs):
         raise DependencyException('Method "get_pkgconfig_variable()" is '
@@ -270,7 +273,17 @@ class InternalDependency(Dependency):
         return InternalDependency(
             self.version, final_includes, final_compile_args,
             final_link_args, final_libraries, final_whole_libraries,
-            final_sources, final_deps)
+            final_sources, final_deps, self.variables)
+
+    def get_variable(self, *, cmake: T.Optional[str] = None, pkgconfig: T.Optional[str] = None,
+                     configtool: T.Optional[str] = None, internal: T.Optional[str] = None,
+                     default_value: T.Optional[str] = None,
+                     pkgconfig_define: T.Optional[T.List[str]] = None) -> T.Union[str, T.List[str]]:
+        val = self.variables.get(internal, default_value)
+        if val is not None:
+            return val
+        raise DependencyException('Could not get an internal variable and no default provided for {!r}'.format(self))
+
 
 class HasNativeKwarg:
     def __init__(self, kwargs):
@@ -554,7 +567,8 @@ class ConfigToolDependency(ExternalDependency):
         return self.type_name
 
     def get_variable(self, *, cmake: T.Optional[str] = None, pkgconfig: T.Optional[str] = None,
-                     configtool: T.Optional[str] = None, default_value: T.Optional[str] = None,
+                     configtool: T.Optional[str] = None, internal: T.Optional[str] = None,
+                     default_value: T.Optional[str] = None,
                      pkgconfig_define: T.Optional[T.List[str]] = None) -> T.Union[str, T.List[str]]:
         if configtool:
             # In the not required case '' (empty string) will be returned if the
@@ -1013,7 +1027,8 @@ class PkgConfigDependency(ExternalDependency):
         return self.type_name
 
     def get_variable(self, *, cmake: T.Optional[str] = None, pkgconfig: T.Optional[str] = None,
-                     configtool: T.Optional[str] = None, default_value: T.Optional[str] = None,
+                     configtool: T.Optional[str] = None, internal: T.Optional[str] = None,
+                     default_value: T.Optional[str] = None,
                      pkgconfig_define: T.Optional[T.List[str]] = None) -> T.Union[str, T.List[str]]:
         if pkgconfig:
             kwargs = {}
@@ -1550,7 +1565,8 @@ project(MesonTemp LANGUAGES {})
         return ''
 
     def get_variable(self, *, cmake: T.Optional[str] = None, pkgconfig: T.Optional[str] = None,
-                     configtool: T.Optional[str] = None, default_value: T.Optional[str] = None,
+                     configtool: T.Optional[str] = None, internal: T.Optional[str] = None,
+                     default_value: T.Optional[str] = None,
                      pkgconfig_define: T.Optional[T.List[str]] = None) -> T.Union[str, T.List[str]]:
         if cmake:
             try:
diff --git a/mesonbuild/interpreter.py b/mesonbuild/interpreter.py
index f1ed2d4..908a555 100644
--- a/mesonbuild/interpreter.py
+++ b/mesonbuild/interpreter.py
@@ -483,7 +483,8 @@ class DependencyHolder(InterpreterObject, ObjectHolder):
 
     @FeatureNew('dep.get_variable', '0.51.0')
     @noPosargs
-    @permittedKwargs({'cmake', 'pkgconfig', 'configtool', 'default_value', 'pkgconfig_define'})
+    @permittedKwargs({'cmake', 'pkgconfig', 'configtool', 'internal', 'default_value', 'pkgconfig_define'})
+    @FeatureNewKwargs('dep.get_variable', '0.54.0', ['internal'])
     def variable_method(self, args, kwargs):
         return self.held_object.get_variable(**kwargs)
 
@@ -2087,6 +2088,7 @@ permitted_kwargs = {'add_global_arguments': {'language', 'native'},
                                            'link_args',
                                            'link_whole',
                                            'version',
+                                           'variables',
                                            },
                     'executable': build.known_exe_kwargs,
                     'find_program': {'required', 'native', 'version', 'dirs'},
@@ -2385,6 +2387,7 @@ class Interpreter(InterpreterBase):
         return [mesonlib.File.from_source_file(self.environment.source_dir, self.subdir, fname) for fname in args]
 
     @FeatureNewKwargs('declare_dependency', '0.46.0', ['link_whole'])
+    @FeatureNewKwargs('declare_dependency', '0.54.0', ['variables'])
     @permittedKwargs(permitted_kwargs['declare_dependency'])
     @noPosargs
     def func_declare_dependency(self, node, args, kwargs):
@@ -2399,6 +2402,12 @@ class Interpreter(InterpreterBase):
         deps = extract_as_list(kwargs, 'dependencies', unholder=True)
         compile_args = mesonlib.stringlistify(kwargs.get('compile_args', []))
         link_args = mesonlib.stringlistify(kwargs.get('link_args', []))
+        variables = kwargs.get('variables', {})
+        if not isinstance(variables, dict):
+            raise InterpreterException('variables must be a dict.')
+        if not all(isinstance(v, str) for v in variables.values()):
+            # Because that is how they will come from pkg-config and cmake
+            raise InterpreterException('variables values be strings.')
         final_deps = []
         for d in deps:
             try:
@@ -2413,7 +2422,8 @@ class Interpreter(InterpreterBase):
                 raise InterpreterException('''Entries in "link_with" may only be self-built targets,
 external dependencies (including libraries) must go to "dependencies".''')
         dep = dependencies.InternalDependency(version, incs, compile_args,
-                                              link_args, libs, libs_whole, sources, final_deps)
+                                              link_args, libs, libs_whole, sources, final_deps,
+                                              variables)
         return DependencyHolder(dep, self.subproject)
 
     @noKwargs
diff --git a/mesonbuild/modules/gnome.py b/mesonbuild/modules/gnome.py
index 9bd7a99..3d5d718 100644
--- a/mesonbuild/modules/gnome.py
+++ b/mesonbuild/modules/gnome.py
@@ -1692,7 +1692,7 @@ G_END_DECLS'''
         # - add relevant directories to include dirs
         incs = [build.IncludeDirs(state.subdir, ['.'] + vapi_includes, False)]
         sources = [vapi_target] + vapi_depends
-        rv = InternalDependency(None, incs, [], [], link_with, [], sources, [])
+        rv = InternalDependency(None, incs, [], [], link_with, [], sources, [], {})
         created_values.append(rv)
         return ModuleReturnValue(rv, created_values)
 
diff --git a/test cases/common/218 dependency get_variable method/meson.build b/test cases/common/218 dependency get_variable method/meson.build
index 72e65ee..8c189bb 100644
--- a/test cases/common/218 dependency get_variable method/meson.build
+++ b/test cases/common/218 dependency get_variable method/meson.build
@@ -47,6 +47,15 @@ else
         'cmake config-tool got default when we shouldn\'t have.')
 endif
 
+idep = declare_dependency(variables : {'foo' : 'value'})
+assert(idep.get_variable(pkgconfig : 'foo', cmake : 'foo', configtool : 'foo',
+                         internal : 'foo', default_value : default) == 'value',
+       'internal got default when it shouldn\'t have.')
+assert(idep.get_variable(pkgconfig : 'foo', cmake : 'foo', configtool : 'foo',
+                         internal : 'bar', default_value : default) == default,
+       'internal didn\'t default when it should have.')
+
 idep = declare_dependency()
-assert(idep.get_variable(pkgconfig : 'foo', cmake : 'foo', configtool : 'foo', default_value : default) == default,
-       'Got something other than default from an internal dependency')
+assert(idep.get_variable(pkgconfig : 'foo', cmake : 'foo', configtool : 'foo',
+                         default_value : default) == default,
+       'something went wrong with an InternalDependency with no variables.')