Do not retain a name string for generated module maps

cc/private/cc_info.bzl

@@ -152,23 +152,91 @@ _ModuleMapInfo = provider(
     "ModuleMapInfo",
     fields = {
         "file": "The module map file.",
-        "name": "The name of the module.",
+        "name": "The name of the module or None if the module is named after the label of the target that generated the module map file (see get_module_map_name).",
     },
 )
 
-def create_module_map(*, file, name):
+def create_module_map(*, file, name = None):
     """
     Creates a module map struct.
 
     Args:
         file: The module map file.
-        name: The name of the module.
+        name: The name of the module. If None (the default), the module is
+          named after the label of the target that generated the module map
+          file. Prefer the default: it avoids retaining a name string per
+          module map as the name is derived on demand from `file.owner`.
     Returns:
         A module map struct.
     """
     check_private_api()
     return _ModuleMapInfo(file = file, name = name)
 
+def module_map_name_for_label(label):
+    """
+    Returns the module name for a module map named after the given label.
+
+    The name is the label's unambiguous canonical form, except that
+    main-repository labels do not carry the leading double-at prefix (see
+    get_module_map_name).
+
+    Args:
+        label: The Label the module is named after.
+    Returns:
+        The name of the module as a string.
+    """
+    label_string = str(label)
+
+    # buildifier: disable=canonical-repository
+    if label_string.startswith("@@//"):
+        return label_string[2:]
+    return label_string
+
+def get_module_map_name(module_map):
+    """
+    Returns the name of the module described by a module map struct.
+
+    Module maps generated for a target are named after the target's label,
+    rendered in its unambiguous canonical form, except that main-repository
+    labels do not carry the leading double-at prefix (for example "//pkg:lib"
+    for a main-repository target). Names of targets in external repositories
+    are thus valid label strings, while main-repository names match the
+    traditional module name format.
+
+    Args:
+        module_map: The module map struct.
+    Returns:
+        The name of the module as a string.
+    """
+    if module_map.name != None:
+        return module_map.name
+    return module_map_name_for_label(module_map.file.owner)
+
+def get_module_map_label(module_map):
+    """
+    Returns the label a module map struct is named after.
+
+    This is only valid for module maps whose name is (derived from) a label,
+    which is the case for all module maps generated for a target, including
+    separate module maps. It is not valid for module maps with special names
+    such as the crosstool module map.
+
+    Args:
+        module_map: The module map struct.
+    Returns:
+        The Label the module's name refers to.
+    """
+    if module_map.name == None:
+        return module_map.file.owner
+
+    # Module map names of main-repository targets lack the leading "@@" (see
+    # get_module_map_name), which has to be restored for parsing to ensure
+    # that the name is not resolved relative to this file's repository.
+    name = module_map.name
+
+    # buildifier: disable=canonical-repository
+    return Label(name if name.startswith("@") else "@@" + name)
+
 def create_separate_module_map(module_map):
     """
     Creates a separate module map struct.
@@ -178,7 +246,7 @@ def create_separate_module_map(module_map):
     Returns:
         A module map struct.
     """
-    return _ModuleMapInfo(file = module_map.file, name = module_map.name + ".sep")
+    return _ModuleMapInfo(file = module_map.file, name = get_module_map_name(module_map) + ".sep")
 
 def create_linking_context(
         *,

cc/private/compile/cc_compilation_helper.bzl

@@ -21,7 +21,7 @@ load(
     "repository_exec_path",
 )
 load("//cc/common:semantics.bzl", "STRIP_INCLUDE_PREFIX_APPLIES_TO_TEXTUAL_HEADERS", "USE_EXEC_ROOT_FOR_VIRTUAL_INCLUDES_SYMLINKS")
-load("//cc/private:cc_info.bzl", "create_compilation_context", "create_module_map")
+load("//cc/private:cc_info.bzl", "create_compilation_context", "create_module_map", "get_module_map_name", "module_map_name_for_label")
 load("//cc/private:cc_internal.bzl", _cc_internal = "cc_internal")
 
 _VIRTUAL_INCLUDES_DIR = "_virtual_includes"
@@ -254,7 +254,8 @@ _ModuleMapInfo = provider(
 def _module_map_struct_to_module_map_content(parameters, tree_expander):
     lines = []
     module_map = parameters.module_map
-    lines.append("module \"%s\" {" % module_map.name)
+    module_name = get_module_map_name(module_map)
+    lines.append("module \"%s\" {" % module_name)
     lines.append("  export *")
 
     def expanded(artifacts):
@@ -326,10 +327,10 @@ def _module_map_struct_to_module_map_content(parameters, tree_expander):
 
     dependency_module_maps = parameters.dependency_module_maps.to_list()
     for dep in dependency_module_maps:
-        lines.append("  use \"" + dep.name + "\"")
+        lines.append("  use \"" + get_module_map_name(dep) + "\"")
 
     if parameters.separate_module_headers:
-        separate_name = module_map.name + ".sep"
+        separate_name = module_name + ".sep"
         lines.append("  use \"" + separate_name + "\"")
         lines.append("}")
         lines.append("module \"" + separate_name + "\" {")
@@ -343,14 +344,14 @@ def _module_map_struct_to_module_map_content(parameters, tree_expander):
             added_paths.add(header.path)
 
         for dep in dependency_module_maps:
-            lines.append("  use \"" + dep.name + "\"")
+            lines.append("  use \"" + get_module_map_name(dep) + "\"")
 
     lines.append("}")
 
     if parameters.extern_dependencies:
         for dep in dependency_module_maps:
             lines.append(
-                "extern module \"" + dep.name + "\" \"" +
+                "extern module \"" + get_module_map_name(dep) + "\" \"" +
                 parameters.leading_periods + dep.file.path + "\"",
             )
 
@@ -565,10 +566,14 @@ def _init_cc_compilation_context(
     header_module = None
     if _enabled(feature_configuration, "module_maps"):
         if not module_map:
-            module_map = create_module_map(
-                file = actions.declare_file(label.name + ".cppmap"),
-                name = label.workspace_name + "//" + label.package + ":" + label.name,
-            )
+            file = actions.declare_file(label.name + ".cppmap")
+
+            # If compile() is called with a name that differs from the
+            # declaring target's name (e.g. by an aspect), the module name
+            # cannot be derived from the file's owner and has to be stored
+            # explicitly.
+            name = None if file.owner == label else module_map_name_for_label(label)
+            module_map = create_module_map(file = file, name = name)
 
         # There are different modes for module compilation:
         # 1. We create the module map and compile the module so that libraries depending on us can

cc/private/compile/compile.bzl

@@ -36,6 +36,8 @@ load(
     "create_cc_compilation_context_with_cpp20_modules",
     "create_compilation_context_with_extra_header_tokens",
     "create_separate_module_map",
+    "get_module_map_label",
+    "get_module_map_name",
 )
 load("//cc/private:cc_internal.bzl", _cc_internal = "cc_internal")
 load("//cc/private/compile:cc_compilation_helper.bzl", "cc_compilation_helper", "dotd_files_enabled", "serialized_diagnostics_file_enabled")
@@ -543,13 +545,10 @@ def _create_scan_deps_action(
             ),
         )
     specific_compile_build_variables = get_specific_compile_build_variables(
-        feature_configuration,
         use_pic = use_pic,
         source_file = source_artifact,
         output_file = ddi_file,
         dotd_file = dotd_file,
-        cpp_module_map = cc_compilation_context._module_map,
-        direct_module_maps = cc_compilation_context._direct_module_maps,
         user_compile_flags = get_copts(
             language = language,
             cpp_configuration = cpp_configuration,
@@ -846,7 +845,6 @@ def _create_cc_compile_actions_with_cpp20_module_helper(
             common_compile_variables = common_compile_build_variables,
             fdo_build_variables = fdo_build_variables,
             output_category = artifact_category.CLIF_OUTPUT_PROTO if cpp_source.type == CPP_SOURCE_TYPE_CLIF_INPUT_PROTO else artifact_category.OBJECT_FILE,
-            cpp_module_map = cc_compilation_context._module_map,
             add_object = True,
             enable_coverage = is_code_coverage_enabled,
             generate_dwo = should_create_per_object_debug_info(feature_configuration, cpp_configuration),
@@ -994,7 +992,6 @@ def _create_cc_compile_actions_with_cpp20_module_helper(
             common_compile_variables = common_compile_build_variables,
             fdo_build_variables = fdo_build_variables,
             output_category = artifact_category.CLIF_OUTPUT_PROTO if cpp_source.type == CPP_SOURCE_TYPE_CLIF_INPUT_PROTO else artifact_category.OBJECT_FILE,
-            cpp_module_map = cc_compilation_context._module_map,
             add_object = True,
             enable_coverage = is_code_coverage_enabled,
             generate_dwo = should_create_per_object_debug_info(feature_configuration, cpp_configuration),
@@ -1165,7 +1162,7 @@ def _create_cc_compile_actions(
 
     if _should_provide_header_modules(feature_configuration, private_headers, public_headers):
         cpp_module_map = cc_compilation_context._module_map
-        module_map_label = Label(cpp_module_map.name)
+        module_map_label = get_module_map_label(cpp_module_map)
         modules = _create_module_action(
             action_construction_context = action_construction_context,
             cc_compilation_context = cc_compilation_context,
@@ -1211,6 +1208,7 @@ def _create_cc_compile_actions(
                 fdo_build_variables = fdo_build_variables,
                 outputs = outputs,
                 cpp_module_map = separate_cpp_module_map,
+                module_name = get_module_map_name(separate_cpp_module_map),
                 language = language,
                 additional_compilation_inputs = [],
                 additional_include_scanning_roots = [],
@@ -1277,7 +1275,6 @@ def _create_cc_compile_actions(
                 common_compile_variables = common_compile_build_variables,
                 fdo_build_variables = fdo_build_variables,
                 output_category = (artifact_category.CLIF_OUTPUT_PROTO if source_type == CPP_SOURCE_TYPE_CLIF_INPUT_PROTO else artifact_category.OBJECT_FILE),
-                cpp_module_map = cc_compilation_context._module_map,
                 add_object = True,
                 enable_coverage = is_code_coverage_enabled,
                 generate_dwo = should_create_per_object_debug_info(feature_configuration, cpp_configuration),
@@ -1364,14 +1361,11 @@ def _create_cc_compile_actions(
             ),
         ) if serialized_diagnostics_file_enabled(feature_configuration) else None
         specific_compile_build_variables = get_specific_compile_build_variables(
-            feature_configuration,
             use_pic = generate_pic_action,
             source_file = source_file,
             output_file = output_file,
             dotd_file = dotd_file,
             diagnostics_file = diagnostics_file,
-            cpp_module_map = cc_compilation_context._module_map,
-            direct_module_maps = cc_compilation_context._direct_module_maps,
             user_compile_flags = get_copts(
                 language = language,
                 cpp_configuration = cpp_configuration,
@@ -1429,7 +1423,6 @@ def _create_pic_nopic_compile_source_actions(
         common_compile_variables,
         fdo_build_variables,
         output_category,
-        cpp_module_map,
         add_object,
         enable_coverage,
         generate_dwo,
@@ -1441,7 +1434,8 @@ def _create_pic_nopic_compile_source_actions(
         generate_pic_action,
         generate_no_pic_action,
         enable_dotd_files,
-        progress_message_prefix):
+        progress_message_prefix,
+        module_name = None):
     results = []
     if generate_pic_action:
         pic_object = _create_compile_source_action(
@@ -1463,7 +1457,7 @@ def _create_pic_nopic_compile_source_actions(
             common_compile_variables = common_compile_variables,
             fdo_build_variables = fdo_build_variables,
             output_category = output_category,
-            cpp_module_map = cpp_module_map,
+            module_name = module_name,
             add_object = add_object,
             enable_coverage = enable_coverage,
             generate_dwo = generate_dwo,
@@ -1500,7 +1494,7 @@ def _create_pic_nopic_compile_source_actions(
             common_compile_variables = common_compile_variables,
             fdo_build_variables = fdo_build_variables,
             output_category = output_category,
-            cpp_module_map = cpp_module_map,
+            module_name = module_name,
             add_object = add_object,
             enable_coverage = enable_coverage,
             generate_dwo = generate_dwo,
@@ -1538,7 +1532,6 @@ def _create_compile_source_action(
         common_compile_variables,
         fdo_build_variables,
         output_category,
-        cpp_module_map,
         add_object,
         enable_coverage,
         generate_dwo,
@@ -1549,6 +1542,7 @@ def _create_compile_source_action(
         additional_include_scanning_roots,
         use_pic,
         enable_dotd_files,
+        module_name = None,
         additional_build_variables = {},
         action_name = None,
         additional_outputs = [],
@@ -1651,9 +1645,7 @@ def _create_compile_source_action(
         dotd_file = dotd_file,
         diagnostics_file = diagnostics_file,
         use_pic = use_pic,
-        cpp_module_map = cpp_module_map,
-        feature_configuration = feature_configuration,
-        direct_module_maps = cc_compilation_context._direct_module_maps,
+        module_name = module_name,
         fdo_build_variables = fdo_build_variables,
         additional_build_variables = additional_build_variables,
     )
@@ -1864,9 +1856,6 @@ def _create_temps_action(
         dotd_file = preprocess_dotd_file,
         diagnostics_file = preprocess_diagnostics_file,
         use_pic = use_pic,
-        cpp_module_map = cc_compilation_context._module_map,
-        direct_module_maps = cc_compilation_context._direct_module_maps,
-        feature_configuration = feature_configuration,
         fdo_build_variables = fdo_build_variables,
         additional_build_variables = {"output_preprocess_file": preprocess_object_file.path},
     )
@@ -1883,9 +1872,6 @@ def _create_temps_action(
         dotd_file = assembly_dotd_file,
         diagnostics_file = assembly_diagnostics_file,
         use_pic = use_pic,
-        cpp_module_map = cc_compilation_context._module_map,
-        direct_module_maps = cc_compilation_context._direct_module_maps,
-        feature_configuration = feature_configuration,
         fdo_build_variables = fdo_build_variables,
         additional_build_variables = {"output_assembly_file": assembly_object_file.path},
     )
@@ -2048,9 +2034,6 @@ def _create_module_codegen_action(
         dotd_file = dotd_file,
         diagnostics_file = diagnostics_file,
         use_pic = use_pic,
-        cpp_module_map = cc_compilation_context._module_map,
-        feature_configuration = feature_configuration,
-        direct_module_maps = cc_compilation_context._direct_module_maps,
         fdo_build_variables = fdo_build_variables,
         additional_build_variables = {},
     )
@@ -2121,8 +2104,9 @@ def _create_module_action(
         additional_compilation_inputs,
         additional_include_scanning_roots,
         outputs,
-        progress_message_prefix):
-    module_map_label = Label(cpp_module_map.name)
+        progress_message_prefix,
+        module_name = None):
+    module_map_label = get_module_map_label(cpp_module_map)
     return _create_pic_nopic_compile_source_actions(
         action_construction_context = action_construction_context,
         cc_compilation_context = cc_compilation_context,
@@ -2146,7 +2130,7 @@ def _create_module_action(
         source_artifact = cpp_module_map.file,
         language = language,
         output_category = artifact_category.CPP_MODULE,
-        cpp_module_map = cpp_module_map,
+        module_name = module_name,
         add_object = False,
         enable_coverage = False,
         generate_dwo = False,

cc/private/compile/compile_action_templates.bzl

@@ -170,12 +170,9 @@ def _create_compile_action_template(
         use_pic = use_pic,
     )
     specific_compile_build_variables = get_specific_compile_build_variables(
-        feature_configuration,
         use_pic = use_pic,
         source_file = source_dir,
         output_file = output_dir,
-        cpp_module_map = cc_compilation_context._module_map,
-        direct_module_maps = cc_compilation_context._direct_module_maps,
         user_compile_flags = all_copts,
     )
     dotd_tree_artifact = _maybe_declare_dotd_tree_artifact(