Add include() function

docs/markdown/Reference-manual.md

@@ -674,6 +674,23 @@ hypothetical `testmod` module.
     tmod.do_something()
 ```
 
+### include()
+
+``` meson
+    void include(file, ...)
+```
+
+Executes the `file`. Once that is done, it returns and execution continues on the
+line following this `include()` command. Variables defined in that
+`file` are then available for use in later parts of the
+current build file and in all subsequent build files executed with `subdir()`.
+
+This function has one keyword argument.
+
+ - `if_found` takes one or several dependency objects and will only
+   execute the file if they all return `true` when queried with
+   `.found()`
+
 ### include_directories()
 
 ``` meson
@@ -1165,7 +1182,7 @@ the invocation. All steps executed up to this point are valid and will
 be executed by meson. This means that all targets defined before the call
 of `subdir_done` will be build.
 
-If the current script was called by `subdir` the execution returns to the
+If the current script was called by `subdir` or `include` the execution returns to the
 calling directory and continues as if the script had reached the end.
 If the current script is the top level script meson configures the project
 as defined up to this point.

mesonbuild/interpreter.py

@@ -1666,6 +1666,7 @@ def get_cross_property_method(self, args, kwargs):
                     'executable': build.known_exe_kwargs,
                     'find_program': {'required', 'native'},
                     'generator': {'arguments', 'output', 'depfile', 'capture', 'preserve_path_from'},
+                    'include': {'if_found'},
                     'include_directories': {'is_system'},
                     'install_data': {'install_dir', 'install_mode', 'rename', 'sources'},
                     'install_headers': {'install_dir', 'subdir'},
@@ -1711,6 +1712,7 @@ def __init__(self, build, backend, subproject='', subdir='', subproject_dir='sub
         self.builtin.update({'meson': MesonMain(build, self)})
         self.generators = []
         self.visited_subdirs = {}
+        self.included_files = set()
         self.project_args_frozen = False
         self.global_args_frozen = False  # implies self.project_args_frozen
         self.subprojects = {}
@@ -1761,6 +1763,7 @@ def build_func_dict(self):
                            'files': self.func_files,
                            'find_library': self.func_find_library,
                            'find_program': self.func_find_program,
+                           'include': self.func_include,
                            'include_directories': self.func_include_directories,
                            'import': self.func_import,
                            'install_data': self.func_install_data,
@@ -3226,6 +3229,45 @@ def func_configure_file(self, node, args, kwargs):
             self.build.data.append(build.Data([cfile], idir))
         return mesonlib.File.from_built_file(self.subdir, output)
 
+    @permittedKwargs(permitted_kwargs['include'])
+    def func_include(self, node, args, kwargs):
+        self.validate_arguments(args, 1, [str])
+        mesonlib.check_direntry_issues(args)
+        for i in mesonlib.extract_as_list(kwargs, 'if_found'):
+            if not hasattr(i, 'found_method'):
+                raise InterpreterException('Object used in if_found does not have a found method.')
+            if not i.found_method([], {}):
+                return
+        if os.path.isabs(args[0]):
+            absname = os.path.abspath(args[0])
+        else:
+            absname = os.path.abspath(os.path.join(self.environment.get_source_dir(), self.subdir, args[0]))
+        prev_current_file = self.current_file
+        if absname in self.included_files:
+            raise InvalidArguments('Tried to include file "%s", which has already been included.'
+                                   % absname)
+        self.included_files.add(absname)
+        if absname not in self.build_def_files:
+            self.build_def_files.append(absname)
+        if not os.path.isfile(absname):
+            raise InterpreterException('Non-existent build file {!r}'.format(absname))
+        with open(absname, encoding='utf8') as f:
+            code = f.read()
+        assert(isinstance(code, str))
+        try:
+            codeblock = mparser.Parser(code, self.subdir).parse()
+        except mesonlib.MesonException as me:
+            me.file = self.current_file
+            raise me
+        self.current_file = absname
+        try:
+            self.evaluate_codeblock(codeblock)
+        except mesonlib.MesonException as me:
+            me.file = self.current_file
+            raise me
+        self.included_files.clear()
+        self.current_file = prev_current_file
+
     @permittedKwargs(permitted_kwargs['include_directories'])
     @stringArgs
     def func_include_directories(self, node, args, kwargs):

mesonbuild/interpreterbase.py

@@ -181,12 +181,14 @@ def __init__(self, source_root, subdir):
         self.funcs = {}
         self.builtin = {}
         self.subdir = subdir
+        self.current_file = ''
         self.variables = {}
         self.argument_depth = 0
         self.current_lineno = -1
 
     def load_root_meson_file(self):
         mesonfile = os.path.join(self.source_root, self.subdir, environment.build_filename)
+        self.current_file = mesonfile
         if not os.path.isfile(mesonfile):
             raise InvalidArguments('Missing Meson file in %s' % mesonfile)
         with open(mesonfile, encoding='utf8') as mf:

test cases/common/199 include/included_file

@@ -0,0 +1,2 @@
+executable('test_include', 'main.c')
+

test cases/common/199 include/incr_variable

@@ -0,0 +1 @@
+variable += 1

test cases/common/199 include/main.c

@@ -0,0 +1,5 @@
+int main(int argc, char **argv)
+{
+    return 0;
+}
+

test cases/common/199 include/meson.build

@@ -0,0 +1,18 @@
+# Should read instructions given in included_file
+
+project('example include', 'c')
+
+variable = 1
+
+assert(variable == 1, 'variable doesn\'t have correct value')
+
+# Check whether it's possible to include the same file several times
+include('incr_variable')
+include('incr_variable')
+include('incr_variable')
+
+assert(variable == 4, 'variable doesn\'t have correct value')
+
+# An executable is declared in included_file
+include('included_file')
+

test cases/common/200 include if_found/included_file

@@ -0,0 +1 @@
+variable = 5

test cases/common/200 include if_found/meson.build

@@ -0,0 +1,8 @@
+project('subdir if found', 'c')
+
+not_found_dep = dependency('nonexisting', required : false)
+
+variable = 3
+
+include('included_file', if_found : not_found_dep)
+assert(variable == 3, 'included_file was unexpectedly included.')

test cases/failing/75 missing included file/meson.build

@@ -0,0 +1,6 @@
+# Should fail because included_file is missing
+
+project('missing included file', 'c')
+
+include('included_file')
+

test cases/failing/76 included file detected cyclic dependency/included_file1

@@ -0,0 +1 @@
+include('included_file2')

test cases/failing/76 included file detected cyclic dependency/included_file2

@@ -0,0 +1 @@
+include('included_file1')

test cases/failing/76 included file detected cyclic dependency/meson.build

@@ -0,0 +1,7 @@
+# Should fail because included_file1 includes included_file2 and
+# included_file2 includes included_file1
+
+project('included file detected cyclic dependency', 'c')
+
+include('included_file2')
+