From ff0551c58b185c769ace0d8747a0e8a2985a1412 Mon Sep 17 00:00:00 2001
From: Jussi Pakkanen <jpakkane@gmail.com>
Date: Sat, 15 Oct 2016 15:21:55 +0300
Subject: [PATCH] Can query pkg-config variables from the system. Closes #726.

---
 mesonbuild/dependencies.py                    |  8 +++++---
 mesonbuild/interpreter.py                     | 14 +++++++++++++-
 mesonbuild/modules/gnome.py                   |  4 ++--
 test cases/linuxlike/1 pkg-config/meson.build |  4 ++++
 4 files changed, 24 insertions(+), 6 deletions(-)

diff --git a/mesonbuild/dependencies.py b/mesonbuild/dependencies.py
index 6a4c32c7a2b5..6f7af5842c12 100644
--- a/mesonbuild/dependencies.py
+++ b/mesonbuild/dependencies.py
@@ -59,6 +59,9 @@ def get_exe_args(self):
     def need_threads(self):
         return False
 
+    def get_pkgconfig_variable(self, variable_name):
+        raise MesonException('Tried to get a pkg-config variable from a non-pkgconfig dependency.')
+
 class InternalDependency(Dependency):
     def __init__(self, version, incdirs, compile_args, link_args, libraries, sources, ext_deps):
         super().__init__()
@@ -186,7 +189,7 @@ def _set_libs(self):
                 self.is_libtool = True
             self.libs.append(lib)
 
-    def get_variable(self, variable_name):
+    def get_pkgconfig_variable(self, variable_name):
         ret, out = self._call_pkgbin(['--variable=' + variable_name, self.name])
         variable = ''
         if ret != 0:
@@ -195,8 +198,7 @@ def get_variable(self, variable_name):
                                           (self.type_string, self.name))
         else:
             variable = out.strip()
-        mlog.debug('return of subprocess : %s' % variable)
-
+        mlog.debug('Got pkgconfig variable %s : %s' % (variable_name, variable))
         return variable
 
     def get_modversion(self):
diff --git a/mesonbuild/interpreter.py b/mesonbuild/interpreter.py
index e486ee980939..455c9302c0d2 100644
--- a/mesonbuild/interpreter.py
+++ b/mesonbuild/interpreter.py
@@ -278,7 +278,9 @@ def __init__(self, dep):
         InterpreterObject.__init__(self)
         self.held_object = dep
         self.methods.update({'found' : self.found_method,
-                             'version': self.version_method})
+                             'version': self.version_method,
+                             'get_pkgconfig_variable': self.pkgconfig_method,
+                             })
 
     def found_method(self, args, kwargs):
         return self.held_object.found()
@@ -286,6 +288,16 @@ def found_method(self, args, kwargs):
     def version_method(self, args, kwargs):
         return self.held_object.get_version()
 
+    def pkgconfig_method(self, args, kwargs):
+        if not isinstance(args, list):
+            args = [args]
+        if len(args) != 1:
+            raise InterpreterException('get_pkgconfig_variable takes exactly one argument.')
+        varname = args[0]
+        if not isinstance(varname, str):
+            raise InterpreterException('Variable name must be a string.')
+        return self.held_object.get_pkgconfig_variable(varname)
+
 class InternalDependencyHolder(InterpreterObject):
     def __init__(self, dep):
         InterpreterObject.__init__(self)
diff --git a/mesonbuild/modules/gnome.py b/mesonbuild/modules/gnome.py
index be111ea7dd60..a5181d3236f5 100644
--- a/mesonbuild/modules/gnome.py
+++ b/mesonbuild/modules/gnome.py
@@ -180,7 +180,7 @@ def get_dependencies_flags(self, deps, state, depends=None):
                     ldflags.update([lib])
 
                 if isinstance(dep, dependencies.PkgConfigDependency):
-                    girdir = dep.get_variable("girdir")
+                    girdir = dep.get_pkgconfig_variable("girdir")
                     if girdir:
                         gi_includes.update([girdir])
             elif isinstance(dep, (build.StaticLibrary, build.SharedLibrary)):
@@ -335,7 +335,7 @@ def generate_gir(self, state, args, kwargs):
                             )
                         ]
             elif isinstance(dep, dependencies.PkgConfigDependency):
-                girdir = dep.get_variable("girdir")
+                girdir = dep.get_pkgconfig_variable("girdir")
                 if girdir:
                     typelib_cmd += ["--includedir=%s" % (girdir, )]
 
diff --git a/test cases/linuxlike/1 pkg-config/meson.build b/test cases/linuxlike/1 pkg-config/meson.build
index a18acc5cee44..13361a7f36e4 100644
--- a/test cases/linuxlike/1 pkg-config/meson.build	
+++ b/test cases/linuxlike/1 pkg-config/meson.build	
@@ -9,6 +9,10 @@ assert(dep.version().version_compare('>=1.2.8'), 'Pkg-config version numbers exp
 
 test('zlibtest', exe)
 
+zprefix = dep.get_pkgconfig_variable('prefix') # Always set but we can't be sure what the value is.
+# pkg-config returns empty string for not defined variables
+assert(dep.get_pkgconfig_variable('nonexisting') == '', 'Value of unknown variable is not empty.')
+
 # Test that dependencies of dependencies work.
 dep2 = declare_dependency(dependencies : dep)
 exe2 = executable('zlibprog2', 'prog.c', dependencies : dep2)