Allow user to specify subproject directory in project definition

project() now takes an optional keyword argument `subproject_dir` which specifies
the directory in which Meson will look for subproject. This argument is ignored
in subprojects as all subprojects are owned by the top level project.

subproject() now looks for the subproject in ${MESON_SOURCE_ROOT}/${SUBPROJECT_DIR}/foo
where SUBPROJECT_DIR can be assigned using project() in the top level project.

interpreter.py

@@ -723,15 +723,16 @@ class MesonMain(InterpreterObject):
         return self.build.environment.coredata.unity
 
     def is_subproject_method(self, args, kwargs):
-        return self.interpreter.subproject != ''
+        return self.interpreter.is_subproject()
 
 class Interpreter():
 
-    def __init__(self, build, subproject='', subdir=''):
+    def __init__(self, build, subproject='', subdir='', subproject_dir='subprojects'):
         self.build = build
         self.subproject = subproject
         self.subdir = subdir
         self.source_root = build.environment.get_source_dir()
+        self.subproject_dir = subproject_dir
         option_file = os.path.join(self.source_root, self.subdir, 'meson_options.txt')
         if os.path.exists(option_file):
             oi = optinterpreter.OptionInterpreter(self.subproject,\
@@ -1040,7 +1041,7 @@ class Interpreter():
         dirname = args[0]
         if self.subdir != '':
             segs = os.path.split(self.subdir)
-            if len(segs) != 2 or segs[0] != 'subprojects':
+            if len(segs) != 2 or segs[0] != self.subproject_dir:
                 raise InterpreterException('Subprojects must be defined at the root directory.')
         if dirname in self.subproject_stack:
             fullstack = self.subproject_stack + [dirname]
@@ -1048,16 +1049,16 @@ class Interpreter():
             raise InterpreterException('Recursive include of subprojects: %s.' % incpath)
         if dirname in self.subprojects:
             return self.subprojects[dirname]
-        subdir = os.path.join('subprojects', dirname)
-        r = wrap.Resolver(os.path.join(self.build.environment.get_source_dir(), 'subprojects'))
+        subdir = os.path.join(self.subproject_dir, dirname)
+        r = wrap.Resolver(os.path.join(self.build.environment.get_source_dir(), self.subproject_dir))
         resolved = r.resolve(dirname)
         if resolved is None:
             raise InterpreterException('Subproject directory does not exist and can not be downloaded.')
-        subdir = os.path.join('subprojects', resolved)
+        subdir = os.path.join(self.subproject_dir, resolved)
         os.makedirs(os.path.join(self.build.environment.get_build_dir(), subdir), exist_ok=True)
         self.global_args_frozen = True
         mlog.log('\nExecuting subproject ', mlog.bold(dirname), '.\n', sep='')
-        subi = Interpreter(self.build, dirname, subdir)
+        subi = Interpreter(self.build, dirname, subdir, self.subproject_dir)
         subi.subprojects = self.subprojects
 
         subi.subproject_stack = self.subproject_stack + [dirname]
@@ -1075,7 +1076,7 @@ class Interpreter():
         if len(args) != 1:
             raise InterpreterException('Argument required for get_option.')
         optname = args[0]
-        if self.subproject != '':
+        if self.is_subproject():
             optname = self.subproject + ':' + optname
         try:
             return self.environment.get_coredata().get_builtin_option(optname)
@@ -1092,14 +1093,19 @@ class Interpreter():
         return ConfigurationDataHolder()
 
     @stringArgs
-    @noKwargs
     def func_project(self, node, args, kwargs):
         if len(args)< 2:
             raise InvalidArguments('Not enough arguments to project(). Needs at least the project name and one language')
-        if self.subproject == '':
+        if list(kwargs.keys()) != ['subproject_dir'] and len(kwargs) != 0:
+            raise InvalidArguments('project() only accepts the keyword argument "subproject_dir"')
+
+        if not self.is_subproject():
             self.build.project_name = args[0]
         if self.subproject in self.build.projects:
             raise InvalidCode('Second call to project().')
+        if not self.is_subproject() and 'subproject_dir' in kwargs:
+            self.subproject_dir = kwargs['subproject_dir']
+
         self.build.projects[self.subproject] = args[0]
         mlog.log('Project name: ', mlog.bold(args[0]), sep='')
         self.add_languages(node, args[1:])
@@ -1377,7 +1383,7 @@ class Interpreter():
         self.validate_arguments(args, 1, [str])
         if '..' in args[0]:
             raise InvalidArguments('Subdir contains ..')
-        if self.subdir == '' and args[0] == 'subprojects':
+        if self.subdir == '' and args[0] == self.subproject_dir:
             raise InvalidArguments('Must not go into subprojects dir with subdir(), use subproject() instead.')
         prev_subdir = self.subdir
         subdir = os.path.join(prev_subdir, args[0])
@@ -1830,3 +1836,6 @@ class Interpreter():
         if len(kwargs) > 0:
             raise InvalidCode('Keyword arguments are invalid in array construction.')
         return arguments
+
+    def is_subproject(self):
+        return self.subproject != ''

test cases/common/82 custom subproject dir/a.c

@@ -0,0 +1,13 @@
+#include<assert.h>
+char func_b();
+char func_c();
+
+int main(int argc, char **argv) {
+    if(func_b() != 'b') {
+        return 1;
+    }
+    if(func_c() != 'c') {
+        return 2;
+    }
+    return 0;
+}

test cases/common/82 custom subproject dir/custom_subproject_dir/B/b.c

@@ -0,0 +1,9 @@
+#include<stdlib.h>
+char func_c();
+
+char func_b() {
+    if(func_c() != 'c') {
+        exit(3);
+    }
+    return 'b';
+}

test cases/common/82 custom subproject dir/custom_subproject_dir/B/meson.build

@@ -0,0 +1,4 @@
+project('B', 'c')
+C = subproject('C')
+c = C.get_variable('c')
+b = shared_library('b', 'b.c', link_with : c)

test cases/common/82 custom subproject dir/custom_subproject_dir/C/c.c

@@ -0,0 +1,3 @@
+char func_c() {
+    return 'c';
+}

test cases/common/82 custom subproject dir/custom_subproject_dir/C/meson.build

@@ -0,0 +1,2 @@
+project('C', 'c')
+c = shared_library('c', 'c.c')

test cases/common/82 custom subproject dir/meson.build

@@ -0,0 +1,10 @@
+project('A', 'c', subproject_dir:'custom_subproject_dir')
+
+B = subproject('B')
+b = B.get_variable('b')
+
+C = subproject('C')
+c = C.get_variable('c')
+
+a = executable('a', 'a.c', link_with : [b, c])
+test('a test', a)