Add --module-name argument to cython command

It can be useful to specify the module name for the output file
directly, rather than working it out from the enclosing file tree -
particularly for out of tree build systems, like Meson.

See: rgommers/scipy#31 (comment)
for background.

Cython/Compiler/CmdLine.py

@@ -145,6 +145,11 @@ def create_cython_argparser():
                       dest='compile_time_env', type=str,
                       action=ParseCompileTimeEnvAction,
                       help='Provides compile time env like DEF would do.')
+    parser.add_argument("--module-name",
+                      dest='module_name', type=str, action='store',
+                      help='Fully qualified module name. If not given, is '
+                           'deduced from the import path if source file is in '
+                           'a package, or equals the filename otherwise.')
     parser.add_argument('sources', nargs='*', default=[])
 
     # TODO: add help
@@ -222,5 +227,14 @@ def parse_command_line(args):
     if len(sources) == 0 and not options.show_version:
         parser.error("cython: Need at least one source file\n")
     if Options.embed and len(sources) > 1:
-        parser.error("cython: Only one source file allowed when using -embed\n")
+        parser.error(
+            "cython: Only one source file allowed when using --embed\n")
+    if options.module_name:
+        if options.timestamps:
+            parser.error(
+                "cython: Cannot use --module-name with --timestamps\n")
+        if len(sources) > 1:
+            parser.error(
+                "cython: Only one source file allowed when using "
+                "--module-name\n")
     return options, sources

Cython/Compiler/Main.py

@@ -584,6 +584,9 @@ def compile_multiple(sources, options):
     a CompilationResultSet. Performs timestamp checking and/or recursion
     if these are specified in the options.
     """
+    if len(sources) > 1 and options.module_name:
+        raise RuntimeError('Full module name can only be set '
+                           'for single source compilation')
     # run_pipeline creates the context
     # context = Context.from_options(options)
     sources = [os.path.abspath(source) for source in sources]
@@ -602,8 +605,9 @@ def compile_multiple(sources, options):
             if (not timestamps) or out_of_date:
                 if verbose:
                     sys.stderr.write("Compiling %s\n" % source)
-
-                result = run_pipeline(source, options, context=context)
+                result = run_pipeline(source, options,
+                                      full_module_name=options.module_name,
+                                      context=context)
                 results.add(source, result)
                 # Compiling multiple sources in one context doesn't quite
                 # work properly yet.

Cython/Compiler/Options.py

@@ -735,6 +735,7 @@ def to_fingerprint(item):
     formal_grammar=False,
     gdb_debug=False,
     compile_time_env=None,
+    module_name=None,
     common_utility_include_dir=None,
     output_dir=None,
     build_dir=None,

Cython/Compiler/Tests/TestCmdLine.py

@@ -495,6 +495,21 @@ def test_warning_extra_dont_overwrite(self):
         self.check_default_global_options()
         self.check_default_options(options, ['compiler_directives'])
 
+    def test_module_name(self):
+        options, sources = parse_command_line([
+            'source.pyx'
+        ])
+        self.assertEqual(options.module_name, None)
+        self.check_default_global_options()
+        self.check_default_options(options)
+        options, sources = parse_command_line([
+            '--module-name', 'foo.bar',
+            'source.pyx'
+        ])
+        self.assertEqual(options.module_name, 'foo.bar')
+        self.check_default_global_options()
+        self.check_default_options(options, ['module_name'])
+
     def test_errors(self):
         def error(*args):
             old_stderr = sys.stderr
@@ -505,7 +520,6 @@ def error(*args):
                 sys.stderr = old_stderr
             self.assertTrue(stderr.getvalue())
 
-        error('-1')
         error('-I')
         error('--version=-a')
         error('--version=--annotate=true')
@@ -514,3 +528,9 @@ def error(*args):
         error('--verbose=1')
         error('--cleanup')
         error('--debug-disposal-code-wrong-name', 'file3.pyx')
+        # No source file (source file appears to be module name).
+        error('--module-name', 'foo.pyx')
+        # Cannot use --module-name with more than one source file.
+        error('--module-name', 'foo.bar', 'foo.pyx', 'bar.pyx')
+        # Cannot use --module-name with --timestamps
+        error('--module-name', 'foo.bar', '--timestamps', 'foo.pyx')