Add partial_dependency method to dependencies

This adds a new method, partial_dependency to all dependencies. These
sub dependencies are copies of the original dependency, but with one or
more of the attributes replaced with an empty list. This allows creating
a sub dependency that has only cflags or drops link_arguments, for
example.

15 files changed, 356 insertions, 2 deletions

diff --git a/docs/markdown/Reference-manual.md b/docs/markdown/Reference-manual.md
index 42abe75..74e7ff2 100644
--- a/docs/markdown/Reference-manual.md
+++ b/docs/markdown/Reference-manual.md
@@ -1827,6 +1827,32 @@ an external dependency with the following methods:
 
  - `version()` is the version number as a string, for example `1.2.8`
 
+ - `partial_dependency(compile_args : false, link_args : false, links : false,
+   includes : false, source : false)` (*added 0.46.0) returns a new dependency
+   object with the same name, version, found status, type name, and methods as
+   the object that called it. This new object will only inherit other
+   attributes from its parent as controlled by keyword arguments.
+
+   If the parent has any dependencies, those will be applied to the new
+   partial dependency with the same rules. So , given:
+
+   ```meson
+   dep1 = declare_dependency(compiler_args : '-Werror=foo', link_with : 'libfoo')
+   dep2 = declare_dependency(compiler_args : '-Werror=bar', dependencies : dep1)
+   dep3 = dep2.partial_dependency(compile_args : true)
+   ```
+
+   dep3 will add `['-Werror=foo', '-Werror=bar']` to the compiler args of
+   any target it is added to, but libfoo will not be added to the link_args.
+
+   The following arguments will add the following attributes:
+
+   - compile_args: any arguments passed to the compiler
+   - link_args: any arguments passed to the linker
+   - links: anything passed via link_with or link_whole
+   - includes: any include_directories
+   - sources: any compiled or static sources the dependency has
+
 ### `disabler` object
 
 A disabler object is an object that behaves in much the same way as
diff --git a/docs/markdown/snippets/partial-dependencies.md b/docs/markdown/snippets/partial-dependencies.md
new file mode 100644
index 0000000..8d2136a
--- /dev/null
+++ b/docs/markdown/snippets/partial-dependencies.md
@@ -0,0 +1,25 @@
+## Added new partial_dependency method to dependencies and libraries
+
+It is now possible to use only part of a dependency in a target. This allows,
+for example, to only use headers with convenience libraries to avoid linking
+to the same library multiple times.
+
+```meson
+
+dep = dependency('xcb')
+
+helper = static_library(
+  'helper',
+  ['helper1.c', 'helper2.c'],
+  dependencies : dep.partial_dependency(includes : true),
+]
+
+final = shared_library(
+  'final',
+  ['final.c'],
+  dependencyes : dep,
+)
+```
+
+A partial dependency will have the same name version as the full dependency it
+is derived from, as well as any values requested.
diff --git a/mesonbuild/dependencies/base.py b/mesonbuild/dependencies/base.py
index 2a19544..27a5fcb 100644
--- a/mesonbuild/dependencies/base.py
+++ b/mesonbuild/dependencies/base.py
@@ -1,4 +1,4 @@
-# Copyright 2013-2017 The Meson development team
+# Copyright 2013-2018 The Meson development team
 
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
@@ -15,6 +15,7 @@
 # This file contains the detection logic for external dependencies.
 # Custom logic for several other packages are in separate files.
 
+import copy
 import os
 import re
 import stat
@@ -146,6 +147,23 @@ class Dependency:
     def get_configtool_variable(self, variable_name):
         raise DependencyException('{!r} is not a config-tool dependency'.format(self.name))
 
+    def get_partial_dependency(self, *, compile_args=False, link_args=False,
+                               links=False, includes=False, sources=False):
+        """Create a new dependency that contains part of the parent dependency.
+
+        The following options can be inherited:
+            links -- all link_with arguemnts
+            includes -- all include_directory and -I/-isystem calls
+            sources -- any source, header, or generated sources
+            compile_args -- any compile args
+            link_args -- any link args
+
+        Additionally the new dependency will have the version parameter of it's
+        parent (if any) and the requested values of any dependencies will be
+        added as well.
+        """
+        RuntimeError('Unreachable code in partial_dependency called')
+
 
 class InternalDependency(Dependency):
     def __init__(self, version, incdirs, compile_args, link_args, libraries, whole_libraries, sources, ext_deps):
@@ -168,6 +186,21 @@ class InternalDependency(Dependency):
         raise DependencyException('Method "get_configtool_variable()" is '
                                   'invalid for an internal dependency')
 
+    def get_partial_dependency(self, *, compile_args=False, link_args=False,
+                               links=False, includes=False, sources=False):
+        compile_args = self.compile_args.copy() if compile_args else []
+        link_args = self.link_args.copy() if link_args else []
+        libraries = self.libraries.copy() if links else []
+        whole_libraries = self.whole_libraries.copy() if links else []
+        sources = self.sources.copy() if sources else []
+        includes = self.include_directories.copy() if includes else []
+        deps = [d.get_partial_dependency(
+            compile_args=compile_args, link_args=link_args, links=links,
+            includes=includes, sources=sources) for d in self.ext_deps]
+        return InternalDependency(
+            self.version, includes, compile_args, link_args, libraries,
+            whole_libraries, sources, deps)
+
 
 class ExternalDependency(Dependency):
     def __init__(self, type_name, environment, language, kwargs):
@@ -211,6 +244,18 @@ class ExternalDependency(Dependency):
     def get_compiler(self):
         return self.compiler
 
+    def get_partial_dependency(self, *, compile_args=False, link_args=False,
+                               links=False, includes=False, sources=False):
+        new = copy.copy(self)
+        if not compile_args:
+            new.compile_args = []
+        if not link_args:
+            new.link_args = []
+        if not sources:
+            new.sources = []
+
+        return new
+
 
 class ConfigToolDependency(ExternalDependency):
 
@@ -887,6 +932,15 @@ class ExternalLibrary(ExternalDependency):
             return []
         return self.link_args
 
+    def get_partial_dependency(self, *, compile_args=False, link_args=False,
+                               links=False, includes=False, sources=False):
+        # External library only has link_args, so ignore the rest of the
+        # interface.
+        new = copy.copy(self)
+        if not link_args:
+            new.link_args = []
+        return new
+
 
 class ExtraFrameworkDependency(ExternalDependency):
     def __init__(self, name, required, path, env, lang, kwargs):
diff --git a/mesonbuild/interpreter.py b/mesonbuild/interpreter.py
index 4e4ba5c..c7841a8 100644
--- a/mesonbuild/interpreter.py
+++ b/mesonbuild/interpreter.py
@@ -275,6 +275,7 @@ class DependencyHolder(InterpreterObject, ObjectHolder):
                              'version': self.version_method,
                              'get_pkgconfig_variable': self.pkgconfig_method,
                              'get_configtool_variable': self.configtool_method,
+                             'partial_dependency': self.partial_dependency_method,
                              })
 
     def type_name_method(self, args, kwargs):
@@ -306,12 +307,18 @@ class DependencyHolder(InterpreterObject, ObjectHolder):
             raise InterpreterException('Variable name must be a string.')
         return self.held_object.get_configtool_variable(varname)
 
+    def partial_dependency_method(self, args, kwargs):
+        if args:
+            raise InterpreterException('partial_dependency takes no positional arguments')
+        return DependencyHolder(self.held_object.get_partial_dependency(**kwargs))
+
 class InternalDependencyHolder(InterpreterObject, ObjectHolder):
     def __init__(self, dep):
         InterpreterObject.__init__(self)
         ObjectHolder.__init__(self, dep)
         self.methods.update({'found': self.found_method,
                              'version': self.version_method,
+                             'partial_dependency': self.partial_dependency_method,
                              })
 
     def found_method(self, args, kwargs):
@@ -320,6 +327,11 @@ class InternalDependencyHolder(InterpreterObject, ObjectHolder):
     def version_method(self, args, kwargs):
         return self.held_object.get_version()
 
+    def partial_dependency_method(self, args, kwargs):
+        if args:
+            raise InterpreterException('get_partial_dependency takes no positional arguments')
+        return DependencyHolder(self.held_object.get_partial_dependency(**kwargs))
+
 class ExternalProgramHolder(InterpreterObject, ObjectHolder):
     def __init__(self, ep):
         InterpreterObject.__init__(self)
@@ -346,7 +358,9 @@ class ExternalLibraryHolder(InterpreterObject, ObjectHolder):
     def __init__(self, el):
         InterpreterObject.__init__(self)
         ObjectHolder.__init__(self, el)
-        self.methods.update({'found': self.found_method})
+        self.methods.update({'found': self.found_method,
+                             'partial_dependency': self.partial_dependency_method,
+                             })
 
     def found(self):
         return self.held_object.found()
@@ -366,6 +380,11 @@ class ExternalLibraryHolder(InterpreterObject, ObjectHolder):
     def get_exe_args(self):
         return self.held_object.get_exe_args()
 
+    def partial_dependency_method(self, args, kwargs):
+        if args:
+            raise InterpreterException('partial_dependency takes no positional arguments')
+        return DependencyHolder(self.held_object.get_partial_dependency(**kwargs))
+
 class GeneratorHolder(InterpreterObject, ObjectHolder):
     def __init__(self, interpreter, args, kwargs):
         InterpreterObject.__init__(self)
diff --git a/test cases/common/191 partial dependency/declare_dependency/headers/foo.c b/test cases/common/191 partial dependency/declare_dependency/headers/foo.c
new file mode 100644
index 0000000..215112c
--- /dev/null
+++ b/test cases/common/191 partial dependency/declare_dependency/headers/foo.c
@@ -0,0 +1,16 @@
+/* Copyright © 2018 Intel Corporation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#error "Included C sources that shouldn't be."
diff --git a/test cases/common/191 partial dependency/declare_dependency/headers/foo.h b/test cases/common/191 partial dependency/declare_dependency/headers/foo.h
new file mode 100644
index 0000000..28c81c9
--- /dev/null
+++ b/test cases/common/191 partial dependency/declare_dependency/headers/foo.h
@@ -0,0 +1,16 @@
+/* Copyright © 2018 Intel Corporation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+int foo(void);
diff --git a/test cases/common/191 partial dependency/declare_dependency/main.c b/test cases/common/191 partial dependency/declare_dependency/main.c
new file mode 100644
index 0000000..e9ed032
--- /dev/null
+++ b/test cases/common/191 partial dependency/declare_dependency/main.c
@@ -0,0 +1,25 @@
+/* Copyright © 2018 Intel Corporation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "foo.h"
+
+int main() {
+    int a = foo();
+    if (a == 1) {
+        return 0;
+    } else {
+        return 1;
+    }
+}
diff --git a/test cases/common/191 partial dependency/declare_dependency/meson.build b/test cases/common/191 partial dependency/declare_dependency/meson.build
new file mode 100644
index 0000000..86e2608
--- /dev/null
+++ b/test cases/common/191 partial dependency/declare_dependency/meson.build
@@ -0,0 +1,28 @@
+# Copyright © 2018 Intel Corporation
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+dec_dep = declare_dependency(
+  sources : files('headers/foo.c'),
+  include_directories : include_directories('headers'),
+)
+
+sub_dep = dec_dep.partial_dependency(includes : true)
+
+dec_exe = executable(
+  'declare_dep',
+  files('main.c', 'other.c'),
+  dependencies : sub_dep,
+)
+
+test('Declare Dependency', dec_exe)
diff --git a/test cases/common/191 partial dependency/declare_dependency/other.c b/test cases/common/191 partial dependency/declare_dependency/other.c
new file mode 100644
index 0000000..b1e199e
--- /dev/null
+++ b/test cases/common/191 partial dependency/declare_dependency/other.c
@@ -0,0 +1,20 @@
+/* Copyright © 2018 Intel Corporation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "foo.h"
+
+int foo(void) {
+    return 1;
+}
diff --git a/test cases/common/191 partial dependency/meson.build b/test cases/common/191 partial dependency/meson.build
new file mode 100644
index 0000000..e908487
--- /dev/null
+++ b/test cases/common/191 partial dependency/meson.build
@@ -0,0 +1,17 @@
+# Copyright © 2018 Intel Corporation
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+project('partial dependency', ['c', 'cpp'])
+
+subdir('declare_dependency')
diff --git a/test cases/frameworks/1 boost/meson.build b/test cases/frameworks/1 boost/meson.build
index df55b30..9399598 100644
--- a/test cases/frameworks/1 boost/meson.build
+++ b/test cases/frameworks/1 boost/meson.build
@@ -31,3 +31,5 @@ test('Boost statictest', staticexe)
 test('Boost UTF test', unitexe)
 test('Boost nomod', nomodexe)
 test('Boost extralib test', extralibexe)
+
+subdir('partial_dep')
diff --git a/test cases/frameworks/1 boost/partial_dep/foo.cpp b/test cases/frameworks/1 boost/partial_dep/foo.cpp
new file mode 100644
index 0000000..da58703
--- /dev/null
+++ b/test cases/frameworks/1 boost/partial_dep/foo.cpp
@@ -0,0 +1,20 @@
+/* Copyright © 2018 Intel Corporation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "foo.hpp"
+
+vec Foo::vector() {
+    return myvec;
+}
diff --git a/test cases/frameworks/1 boost/partial_dep/foo.hpp b/test cases/frameworks/1 boost/partial_dep/foo.hpp
new file mode 100644
index 0000000..393d3f6
--- /dev/null
+++ b/test cases/frameworks/1 boost/partial_dep/foo.hpp
@@ -0,0 +1,27 @@
+/* Copyright © 2018 Intel Corporation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <boost/fusion/container/vector.hpp>
+
+typedef boost::fusion::vector<int> vec;
+
+
+class Foo {
+    public:
+        Foo() {};
+        vec vector();
+    private:
+        const vec myvec = vec(4);
+};
diff --git a/test cases/frameworks/1 boost/partial_dep/main.cpp b/test cases/frameworks/1 boost/partial_dep/main.cpp
new file mode 100644
index 0000000..5138f5c
--- /dev/null
+++ b/test cases/frameworks/1 boost/partial_dep/main.cpp
@@ -0,0 +1,28 @@
+/* Copyright © 2018 Intel Corporation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <iostream>
+#include <boost/fusion/include/at_c.hpp>
+#include "foo.hpp"
+
+
+int main() {
+    auto foo = Foo();
+    vec v = foo.vector();
+    std::cout << boost::fusion::at_c<0>(v) << std::endl;
+
+    return 0;
+}
+
diff --git a/test cases/frameworks/1 boost/partial_dep/meson.build b/test cases/frameworks/1 boost/partial_dep/meson.build
new file mode 100644
index 0000000..9d481bb
--- /dev/null
+++ b/test cases/frameworks/1 boost/partial_dep/meson.build
@@ -0,0 +1,31 @@
+# Copyright © 2018 Intel Corporation
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+dep_boost = dependency('boost')
+dep_boost_headers = dep_boost.partial_dependency(compile_args : true)
+
+libfoo = static_library(
+  'foo',
+  'foo.cpp',
+  dependencies : dep_boost_headers,
+)
+
+exe_external_dep = executable(
+  'external_dep',
+  'main.cpp',
+  dependencies : dep_boost,
+  link_with : libfoo
+)
+
+test('External Dependency', exe_external_dep)