Add an option to dependencies called 'method'. This can be used to

configure a detection method, for those types of dependencies that have
more than one means of detection.

The default detection methods are unchanged if 'method' is not
specified, and all dependencies support the method 'auto', which is the
same as not specifying a method.

The dependencies which do support multiple detection methods
additionally support other values, depending on the dependency.

4 files changed, 174 insertions, 107 deletions

diff --git a/mesonbuild/dependencies.py b/mesonbuild/dependencies.py
index 2b110bb..f3e00ce 100644
--- a/mesonbuild/dependencies.py
+++ b/mesonbuild/dependencies.py
@@ -34,10 +34,20 @@ class DependencyException(MesonException):
     '''Exceptions raised while trying to find dependencies'''
 
 class Dependency:
-    def __init__(self, type_name='unknown'):
+    def __init__(self, type_name, kwargs):
         self.name = "null"
         self.is_found = False
         self.type_name = type_name
+        method = kwargs.get('method', 'auto')
+
+        # Set the detection method. If the method is set to auto, use any available method.
+        # If method is set to a specific string, allow only that detection method.
+        if method == "auto":
+            self.methods = self.get_methods()
+        elif method in self.get_methods():
+            self.methods = [method]
+        else:
+            raise MesonException('Unsupported detection method: {}, allowed methods are {}'.format(method, mlog.format_list(["auto"] + self.get_methods())))
 
     def __repr__(self):
         s = '<{0} {1}: {2}>'
@@ -57,6 +67,9 @@ class Dependency:
         As an example, gtest-all.cc when using GTest."""
         return []
 
+    def get_methods(self):
+        return ['auto']
+
     def get_name(self):
         return self.name
 
@@ -71,7 +84,7 @@ class Dependency:
 
 class InternalDependency(Dependency):
     def __init__(self, version, incdirs, compile_args, link_args, libraries, sources, ext_deps):
-        super().__init__('internal')
+        super().__init__('internal', {})
         self.version = version
         self.include_directories = incdirs
         self.compile_args = compile_args
@@ -95,7 +108,7 @@ class PkgConfigDependency(Dependency):
     class_pkgbin = None
 
     def __init__(self, name, environment, kwargs):
-        Dependency.__init__(self, 'pkgconfig')
+        Dependency.__init__(self, 'pkgconfig', kwargs)
         self.is_libtool = False
         self.required = kwargs.get('required', True)
         self.static = kwargs.get('static', False)
@@ -254,6 +267,9 @@ class PkgConfigDependency(Dependency):
     def get_link_args(self):
         return self.libs
 
+    def get_methods(self):
+        return ['pkgconfig']
+
     def check_pkgconfig(self):
         evar = 'PKG_CONFIG'
         if evar in os.environ:
@@ -322,7 +338,7 @@ class WxDependency(Dependency):
     wx_found = None
 
     def __init__(self, environment, kwargs):
-        Dependency.__init__(self, 'wx')
+        Dependency.__init__(self, 'wx', kwargs)
         self.is_found = False
         self.modversion = 'none'
         if WxDependency.wx_found is None:
@@ -542,7 +558,7 @@ class ExternalLibrary(Dependency):
     # TODO: Add `lang` to the parent Dependency object so that dependencies can
     # be expressed for languages other than C-like
     def __init__(self, name, link_args=None, language=None, silent=False):
-        super().__init__('external')
+        super().__init__('external', {})
         self.name = name
         self.is_found = False
         self.link_args = []
@@ -582,7 +598,7 @@ class BoostDependency(Dependency):
     name2lib = {'test': 'unit_test_framework'}
 
     def __init__(self, environment, kwargs):
-        Dependency.__init__(self, 'boost')
+        Dependency.__init__(self, 'boost', kwargs)
         self.name = 'boost'
         self.environment = environment
         self.libdir = ''
@@ -805,7 +821,7 @@ class BoostDependency(Dependency):
 
 class GTestDependency(Dependency):
     def __init__(self, environment, kwargs):
-        Dependency.__init__(self, 'gtest')
+        Dependency.__init__(self, 'gtest', kwargs)
         self.main = kwargs.get('main', False)
         self.name = 'gtest'
         self.libname = 'libgtest.so'
@@ -882,7 +898,7 @@ class GTestDependency(Dependency):
 
 class GMockDependency(Dependency):
     def __init__(self, environment, kwargs):
-        Dependency.__init__(self, 'gmock')
+        Dependency.__init__(self, 'gmock', kwargs)
         # GMock may be a library or just source.
         # Work with both.
         self.name = 'gmock'
@@ -937,7 +953,7 @@ class GMockDependency(Dependency):
 
 class QtBaseDependency(Dependency):
     def __init__(self, name, env, kwargs):
-        Dependency.__init__(self, name)
+        Dependency.__init__(self, name, kwargs)
         self.name = name
         self.qtname = name.capitalize()
         self.qtver = name[-1]
@@ -964,26 +980,32 @@ class QtBaseDependency(Dependency):
         type_text = 'cross' if env.is_cross_build() else 'native'
         found_msg = '{} {} {{}} dependency (modules: {}) found:' \
                     ''.format(self.qtname, type_text, ', '.join(mods))
-        from_text = '`pkg-config`'
+        from_text = 'pkg-config'
+
+        # Keep track of the detection methods used, for logging purposes.
+        methods = []
         # Prefer pkg-config, then fallback to `qmake -query`
-        self._pkgconfig_detect(mods, env, kwargs)
-        if not self.is_found:
+        if 'pkgconfig' in self.methods:
+            self._pkgconfig_detect(mods, env, kwargs)
+            methods.append('pkgconfig')
+        if not self.is_found and 'qmake' in self.methods:
             from_text = self._qmake_detect(mods, env, kwargs)
-            if not self.is_found:
-                # Reset compile args and link args
-                self.cargs = []
-                self.largs = []
-                from_text = '(checked pkg-config, qmake-{}, and qmake)' \
-                            ''.format(self.name)
-                self.version = 'none'
-                if self.required:
-                    err_msg = '{} {} dependency not found {}' \
-                              ''.format(self.qtname, type_text, from_text)
-                    raise DependencyException(err_msg)
-                if not self.silent:
-                    mlog.log(found_msg.format(from_text), mlog.red('NO'))
-                return
-            from_text = '`{}`'.format(from_text)
+            methods.append('qmake-' + self.name)
+            methods.append('qmake')
+        if not self.is_found:
+            # Reset compile args and link args
+            self.cargs = []
+            self.largs = []
+            from_text = '(checked {})'.format(mlog.format_list(methods))
+            self.version = 'none'
+            if self.required:
+                err_msg = '{} {} dependency not found {}' \
+                          ''.format(self.qtname, type_text, from_text)
+                raise DependencyException(err_msg)
+            if not self.silent:
+                mlog.log(found_msg.format(from_text), mlog.red('NO'))
+            return
+        from_text = '`{}`'.format(from_text)
         if not self.silent:
             mlog.log(found_msg.format(from_text), mlog.green('YES'))
 
@@ -1053,6 +1075,7 @@ class QtBaseDependency(Dependency):
             return
         self.version = re.search(self.qtver + '(\.\d+)+', stdo).group(0)
         # Query library path, header path, and binary path
+        mlog.log("Found qmake:", mlog.bold(self.qmake.get_name()), '(%s)' % self.version)
         stdo = Popen_safe(self.qmake.get_command() + ['-query'])[1]
         qvars = {}
         for line in stdo.split('\n'):
@@ -1092,7 +1115,7 @@ class QtBaseDependency(Dependency):
         libdir = qvars['QT_INSTALL_LIBS']
         for m in modules:
             fname = 'Qt' + m
-            fwdep = ExtraFrameworkDependency(fname, kwargs.get('required', True), libdir)
+            fwdep = ExtraFrameworkDependency(fname, kwargs.get('required', True), libdir, kwargs)
             self.cargs.append('-F' + libdir)
             if fwdep.found():
                 self.is_found = True
@@ -1113,6 +1136,9 @@ class QtBaseDependency(Dependency):
     def get_link_args(self):
         return self.largs
 
+    def get_methods(self):
+        return ['pkgconfig', 'qmake']
+
     def found(self):
         return self.is_found
 
@@ -1150,7 +1176,7 @@ class Qt4Dependency(QtBaseDependency):
 
 class GnuStepDependency(Dependency):
     def __init__(self, environment, kwargs):
-        Dependency.__init__(self, 'gnustep')
+        Dependency.__init__(self, 'gnustep', kwargs)
         self.required = kwargs.get('required', True)
         self.modules = kwargs.get('modules', [])
         self.detect()
@@ -1248,7 +1274,7 @@ why. As a hack filter out everything that is not a flag."""
 
 class AppleFrameworks(Dependency):
     def __init__(self, environment, kwargs):
-        Dependency.__init__(self, 'appleframeworks')
+        Dependency.__init__(self, 'appleframeworks', kwargs)
         modules = kwargs.get('modules', [])
         if isinstance(modules, str):
             modules = [modules]
@@ -1271,31 +1297,33 @@ class AppleFrameworks(Dependency):
 
 class GLDependency(Dependency):
     def __init__(self, environment, kwargs):
-        Dependency.__init__(self, 'gl')
+        Dependency.__init__(self, 'gl', kwargs)
         self.is_found = False
         self.cargs = []
         self.linkargs = []
-        try:
-            pcdep = PkgConfigDependency('gl', environment, kwargs)
-            if pcdep.found():
-                self.type_name = 'pkgconfig'
+        if 'pkgconfig' in self.methods:
+            try:
+                pcdep = PkgConfigDependency('gl', environment, kwargs)
+                if pcdep.found():
+                    self.type_name = 'pkgconfig'
+                    self.is_found = True
+                    self.cargs = pcdep.get_compile_args()
+                    self.linkargs = pcdep.get_link_args()
+                    self.version = pcdep.get_version()
+                    return
+            except Exception:
+                pass
+        if 'system' in self.methods:
+            if mesonlib.is_osx():
                 self.is_found = True
-                self.cargs = pcdep.get_compile_args()
-                self.linkargs = pcdep.get_link_args()
-                self.version = pcdep.get_version()
+                self.linkargs = ['-framework', 'OpenGL']
+                self.version = '1' # FIXME
+                return
+            if mesonlib.is_windows():
+                self.is_found = True
+                self.linkargs = ['-lopengl32']
+                self.version = '1' # FIXME: unfixable?
                 return
-        except Exception:
-            pass
-        if mesonlib.is_osx():
-            self.is_found = True
-            self.linkargs = ['-framework', 'OpenGL']
-            self.version = '1' # FIXME
-            return
-        if mesonlib.is_windows():
-            self.is_found = True
-            self.linkargs = ['-lopengl32']
-            self.version = '1' # FIXME: unfixable?
-            return
 
     def get_link_args(self):
         return self.linkargs
@@ -1303,48 +1331,57 @@ class GLDependency(Dependency):
     def get_version(self):
         return self.version
 
+    def get_methods(self):
+        if mesonlib.is_osx() or mesonlib.is_windows():
+            return ['pkgconfig', 'system']
+        else:
+            return ['pkgconfig']
+
 # There are three different ways of depending on SDL2:
 # sdl2-config, pkg-config and OSX framework
 class SDL2Dependency(Dependency):
     def __init__(self, environment, kwargs):
-        Dependency.__init__(self, 'sdl2')
+        Dependency.__init__(self, 'sdl2', kwargs)
         self.is_found = False
         self.cargs = []
         self.linkargs = []
-        try:
-            pcdep = PkgConfigDependency('sdl2', environment, kwargs)
-            if pcdep.found():
-                self.type_name = 'pkgconfig'
-                self.is_found = True
-                self.cargs = pcdep.get_compile_args()
-                self.linkargs = pcdep.get_link_args()
-                self.version = pcdep.get_version()
-                return
-        except Exception as e:
-            mlog.debug('SDL 2 not found via pkgconfig. Trying next, error was:', str(e))
-            pass
-        sdlconf = shutil.which('sdl2-config')
-        if sdlconf:
-            stdo = Popen_safe(['sdl2-config', '--cflags'])[1]
-            self.cargs = stdo.strip().split()
-            stdo = Popen_safe(['sdl2-config', '--libs'])[1]
-            self.linkargs = stdo.strip().split()
-            stdo = Popen_safe(['sdl2-config', '--version'])[1]
-            self.version = stdo.strip()
-            self.is_found = True
-            mlog.log('Dependency', mlog.bold('sdl2'), 'found:', mlog.green('YES'),
-                     self.version, '(%s)' % sdlconf)
-            return
-        mlog.debug('Could not find sdl2-config binary, trying next.')
-        if mesonlib.is_osx():
-            fwdep = ExtraFrameworkDependency('sdl2', kwargs.get('required', True))
-            if fwdep.found():
+        if 'pkgconfig' in self.methods:
+            try:
+                pcdep = PkgConfigDependency('sdl2', environment, kwargs)
+                if pcdep.found():
+                    self.type_name = 'pkgconfig'
+                    self.is_found = True
+                    self.cargs = pcdep.get_compile_args()
+                    self.linkargs = pcdep.get_link_args()
+                    self.version = pcdep.get_version()
+                    return
+            except Exception as e:
+                mlog.debug('SDL 2 not found via pkgconfig. Trying next, error was:', str(e))
+                pass
+        if 'sdlconfig' in self.methods:
+            sdlconf = shutil.which('sdl2-config')
+            if sdlconf:
+                stdo = Popen_safe(['sdl2-config', '--cflags'])[1]
+                self.cargs = stdo.strip().split()
+                stdo = Popen_safe(['sdl2-config', '--libs'])[1]
+                self.linkargs = stdo.strip().split()
+                stdo = Popen_safe(['sdl2-config', '--version'])[1]
+                self.version = stdo.strip()
                 self.is_found = True
-                self.cargs = fwdep.get_compile_args()
-                self.linkargs = fwdep.get_link_args()
-                self.version = '2' # FIXME
+                mlog.log('Dependency', mlog.bold('sdl2'), 'found:', mlog.green('YES'),
+                         self.version, '(%s)' % sdlconf)
                 return
-        mlog.log('Dependency', mlog.bold('sdl2'), 'found:', mlog.red('NO'))
+            mlog.debug('Could not find sdl2-config binary, trying next.')
+        if 'extraframework' in self.methods:
+            if mesonlib.is_osx():
+                fwdep = ExtraFrameworkDependency('sdl2', kwargs.get('required', True), None, kwargs)
+                if fwdep.found():
+                    self.is_found = True
+                    self.cargs = fwdep.get_compile_args()
+                    self.linkargs = fwdep.get_link_args()
+                    self.version = '2' # FIXME
+                    return
+            mlog.log('Dependency', mlog.bold('sdl2'), 'found:', mlog.red('NO'))
 
     def get_compile_args(self):
         return self.cargs
@@ -1358,9 +1395,15 @@ class SDL2Dependency(Dependency):
     def get_version(self):
         return self.version
 
+    def get_methods(self):
+        if mesonlib.is_osx():
+            return ['pkgconfig', 'sdlconfig', 'extraframework']
+        else:
+            return ['pkgconfig', 'sdlconfig']
+
 class ExtraFrameworkDependency(Dependency):
-    def __init__(self, name, required, path=None):
-        Dependency.__init__(self, 'extraframeworks')
+    def __init__(self, name, required, path, kwargs):
+        Dependency.__init__(self, 'extraframeworks', kwargs)
         self.name = None
         self.detect(name, path)
         if self.found():
@@ -1404,7 +1447,7 @@ class ExtraFrameworkDependency(Dependency):
 
 class ThreadDependency(Dependency):
     def __init__(self, environment, kwargs):
-        super().__init__('threads')
+        super().__init__('threads', {})
         self.name = 'threads'
         self.is_found = True
         mlog.log('Dependency', mlog.bold(self.name), 'found:', mlog.green('YES'))
@@ -1417,28 +1460,29 @@ class ThreadDependency(Dependency):
 
 class Python3Dependency(Dependency):
     def __init__(self, environment, kwargs):
-        super().__init__('python3')
+        super().__init__('python3', kwargs)
         self.name = 'python3'
         self.is_found = False
         # We can only be sure that it is Python 3 at this point
         self.version = '3'
-        try:
-            pkgdep = PkgConfigDependency('python3', environment, kwargs)
-            if pkgdep.found():
-                self.cargs = pkgdep.cargs
-                self.libs = pkgdep.libs
-                self.version = pkgdep.get_version()
-                self.is_found = True
-                return
-        except Exception:
-            pass
+        if 'pkgconfig' in self.methods:
+            try:
+                pkgdep = PkgConfigDependency('python3', environment, kwargs)
+                if pkgdep.found():
+                    self.cargs = pkgdep.cargs
+                    self.libs = pkgdep.libs
+                    self.version = pkgdep.get_version()
+                    self.is_found = True
+                    return
+            except Exception:
+                pass
         if not self.is_found:
-            if mesonlib.is_windows():
+            if mesonlib.is_windows() and 'sysconfig' in self.methods:
                 self._find_libpy3_windows(environment)
-            elif mesonlib.is_osx():
+            elif mesonlib.is_osx() and 'extraframework' in self.methods:
                 # In OSX the Python 3 framework does not have a version
                 # number in its name.
-                fw = ExtraFrameworkDependency('python', False)
+                fw = ExtraFrameworkDependency('python', False, None, kwargs)
                 if fw.found():
                     self.cargs = fw.get_compile_args()
                     self.libs = fw.get_link_args()
@@ -1490,6 +1534,14 @@ class Python3Dependency(Dependency):
     def get_link_args(self):
         return self.libs
 
+    def get_methods(self):
+        if mesonlib.is_windows():
+            return ['pkgconfig', 'sysconfig']
+        elif mesonlib.is_osx():
+            return ['pkgconfig', 'extraframework']
+        else:
+            return ['pkgconfig']
+
     def get_version(self):
         return self.version
 
@@ -1537,7 +1589,7 @@ def find_external_dependency(name, environment, kwargs):
     except Exception as e:
         pkg_exc = e
     if mesonlib.is_osx():
-        fwdep = ExtraFrameworkDependency(name, required)
+        fwdep = ExtraFrameworkDependency(name, required, None, kwargs)
         if required and not fwdep.found():
             m = 'Dependency {!r} not found, tried Extra Frameworks ' \
                 'and Pkg-Config:\n\n' + str(pkg_exc)
diff --git a/mesonbuild/mlog.py b/mesonbuild/mlog.py
index bad756a..82ee6ba 100644
--- a/mesonbuild/mlog.py
+++ b/mesonbuild/mlog.py
@@ -99,3 +99,16 @@ def log(*args, **kwargs):
 
 def warning(*args, **kwargs):
     log(yellow('WARNING:'), *args, **kwargs)
+
+# Format a list for logging purposes as a string. It separates
+# all but the last item with commas, and the last with 'and'.
+def format_list(list):
+    l = len(list)
+    if l > 2:
+        return ' and '.join([', '.join(list[:-1]), list[-1]])
+    elif l == 2:
+        return ' and '.join(list)
+    elif l == 1:
+        return list[0]
+    else:
+        return ''
diff --git a/mesonbuild/modules/qt4.py b/mesonbuild/modules/qt4.py
index 7146739..0386291 100644
--- a/mesonbuild/modules/qt4.py
+++ b/mesonbuild/modules/qt4.py
@@ -24,14 +24,14 @@ from . import ModuleReturnValue
 class Qt4Module(ExtensionModule):
     tools_detected = False
 
-    def _detect_tools(self, env):
+    def _detect_tools(self, env, method):
         if self.tools_detected:
             return
         mlog.log('Detecting Qt4 tools')
         # FIXME: We currently require Qt4 to exist while importing the module.
         # We should make it gracefully degrade and not create any targets if
         # the import is marked as 'optional' (not implemented yet)
-        kwargs = {'required': 'true', 'modules': 'Core', 'silent': 'true'}
+        kwargs = {'required': 'true', 'modules': 'Core', 'silent': 'true', 'method': method}
         qt4 = Qt4Dependency(env, kwargs)
         # Get all tools and then make sure that they are the right version
         self.moc, self.uic, self.rcc = qt4.compilers_detect()
@@ -113,7 +113,8 @@ class Qt4Module(ExtensionModule):
         if not isinstance(sources, list):
             sources = [sources]
         sources += args[1:]
-        self._detect_tools(state.environment)
+        method = kwargs.get('method', 'auto')
+        self._detect_tools(state.environment, method)
         err_msg = "{0} sources specified and couldn't find {1}, " \
                   "please check your qt4 installation"
         if len(moc_headers) + len(moc_sources) > 0 and not self.moc.found():
diff --git a/mesonbuild/modules/qt5.py b/mesonbuild/modules/qt5.py
index 2a87a80..6497694 100644
--- a/mesonbuild/modules/qt5.py
+++ b/mesonbuild/modules/qt5.py
@@ -24,14 +24,14 @@ from . import ModuleReturnValue
 class Qt5Module(ExtensionModule):
     tools_detected = False
 
-    def _detect_tools(self, env):
+    def _detect_tools(self, env, method):
         if self.tools_detected:
             return
         mlog.log('Detecting Qt5 tools')
         # FIXME: We currently require Qt5 to exist while importing the module.
         # We should make it gracefully degrade and not create any targets if
         # the import is marked as 'optional' (not implemented yet)
-        kwargs = {'required': 'true', 'modules': 'Core', 'silent': 'true'}
+        kwargs = {'required': 'true', 'modules': 'Core', 'silent': 'true', 'method': method}
         qt5 = Qt5Dependency(env, kwargs)
         # Get all tools and then make sure that they are the right version
         self.moc, self.uic, self.rcc = qt5.compilers_detect()
@@ -119,7 +119,8 @@ class Qt5Module(ExtensionModule):
         if not isinstance(sources, list):
             sources = [sources]
         sources += args[1:]
-        self._detect_tools(state.environment)
+        method = kwargs.get('method', 'auto')
+        self._detect_tools(state.environment, method)
         err_msg = "{0} sources specified and couldn't find {1}, " \
                   "please check your qt5 installation"
         if len(moc_headers) + len(moc_sources) > 0 and not self.moc.found():