Add index-while-building support (back) to the Swift build rules

When the `swift.index_while_building` feature is set, targets will emit an indexstore directory to the "indexstore" output group.

Unlike the original implementation, this one is focused on the remote indexing use case, so we don't support the old behavior meant for local builds of scanning `--swiftcopt` for a manually-specified path that would be the destination for all index data. Users who want to do that should just pass _all_ of the indexing flags to `--swiftcopt` instead of using this feature.

PiperOrigin-RevId: 459613898
(cherry picked from commit 8150427)

---

Cherry-pick notes: we never removed this. This is mainly just moving things around to make future cherry-picks easier. Though, we did take the `--swiftcopt` change by removing `_is_index_store_path_overridden` (which is a breaking change).

Signed-off-by: Brentley Jones <github@brentleyjones.com>

doc/api.md

@@ -122,28 +122,39 @@ Compiles a Swift module.
 
 **RETURNS**
 
-A tuple containing three elements:
-
-  1.  A Swift module context (as returned by `swift_common.create_module`)
-      that contains the Swift (and potentially C/Objective-C) compilation
-      prerequisites of the compiled module. This should typically be
-      propagated by a `SwiftInfo` provider of the calling rule, and the
-      `CcCompilationContext` inside the Clang module substructure should
-      be propagated by the `CcInfo` provider of the calling rule.
-  2.  A `CcCompilationOutputs` object (as returned by
-      `cc_common.create_compilation_outputs`) that contains the compiled
-      object files.
-  3.  A struct containing:
+A `struct` with the following fields:
+
+  *   `module_context`: A Swift module context (as returned by
+      `swift_common.create_module`) that contains the Swift (and
+      potentially C/Objective-C) compilation prerequisites of the compiled
+      module. This should typically be propagated by a `SwiftInfo`
+      provider of the calling rule, and the `CcCompilationContext` inside
+      the Clang module substructure should be propagated by the `CcInfo`
+      provider of the calling rule.
+
+  *   `compilation_outputs`: A `CcCompilationOutputs` object (as returned
+      by `cc_common.create_compilation_outputs`) that contains the
+      compiled object files.
+
+  *   `supplemental_outputs`: A `struct` representing supplemental,
+      optional outputs. Its fields are:
+
       *   `ast_files`: A list of `File`s output from the `DUMP_AST`
           action.
-      *   `indexstore`: A `File` representing the directory that contains
-          the index store data generated by the compiler if the
-          `"swift.index_while_building"` feature is enabled, otherwise
-          this will be `None`.
+
       *   `const_values_files`: A list of `File`s that contains JSON
           representations of constant values extracted from the source
           files, if requested via a direct dependency.
 
+      *   `indexstore_directory`: A directory-type `File` that represents
+          the indexstore output files created when the feature
+          `swift.index_while_building` is enabled.
+
+      *   `macro_expansion_directory`: A directory-type `File` that
+          represents the location where macro expansion files were written
+          (only in debug/fastbuild and only when the toolchain supports
+          macros).
+
 
 <a id="swift_common.compile_module_interface"></a>
 

proto/swift_proto_utils.bzl

@@ -267,7 +267,7 @@ def compile_swift_protos_for_target(
 
     # Compile the generated Swift source files as a module:
     include_dev_srch_paths = include_developer_search_paths(attr)
-    module_context, cc_compilation_outputs, supplemental_outputs = swift_common.compile(
+    compile_result = swift_common.compile(
         actions = ctx.actions,
         cc_infos = get_providers(compiler_deps, CcInfo),
         copts = ["-parse-as-library"],
@@ -283,11 +283,15 @@ def compile_swift_protos_for_target(
         workspace_name = ctx.workspace_name,
     )
 
+    module_context = compile_result.module_context
+    compilation_outputs = compile_result.compilation_outputs
+    supplemental_outputs = compile_result.supplemental_outputs
+
     # Create the linking context from the compilation outputs:
     linking_context, linking_output = (
         swift_common.create_linking_context_from_compilation_outputs(
             actions = ctx.actions,
-            compilation_outputs = cc_compilation_outputs,
+            compilation_outputs = compilation_outputs,
             feature_configuration = feature_configuration,
             include_dev_srch_paths = include_dev_srch_paths,
             label = target_label,

swift/internal/compiling.bzl

@@ -439,27 +439,38 @@ def compile(
              outputs.
 
     Returns:
-        A tuple containing three elements:
-
-        1.  A Swift module context (as returned by `swift_common.create_module`)
-            that contains the Swift (and potentially C/Objective-C) compilation
-            prerequisites of the compiled module. This should typically be
-            propagated by a `SwiftInfo` provider of the calling rule, and the
-            `CcCompilationContext` inside the Clang module substructure should
-            be propagated by the `CcInfo` provider of the calling rule.
-        2.  A `CcCompilationOutputs` object (as returned by
-            `cc_common.create_compilation_outputs`) that contains the compiled
-            object files.
-        3.  A struct containing:
+        A `struct` with the following fields:
+
+        *   `module_context`: A Swift module context (as returned by
+            `swift_common.create_module`) that contains the Swift (and
+            potentially C/Objective-C) compilation prerequisites of the compiled
+            module. This should typically be propagated by a `SwiftInfo`
+            provider of the calling rule, and the `CcCompilationContext` inside
+            the Clang module substructure should be propagated by the `CcInfo`
+            provider of the calling rule.
+
+        *   `compilation_outputs`: A `CcCompilationOutputs` object (as returned
+            by `cc_common.create_compilation_outputs`) that contains the
+            compiled object files.
+
+        *   `supplemental_outputs`: A `struct` representing supplemental,
+            optional outputs. Its fields are:
+
             *   `ast_files`: A list of `File`s output from the `DUMP_AST`
                 action.
-            *   `indexstore`: A `File` representing the directory that contains
-                the index store data generated by the compiler if the
-                `"swift.index_while_building"` feature is enabled, otherwise
-                this will be `None`.
+
             *   `const_values_files`: A list of `File`s that contains JSON
                 representations of constant values extracted from the source
                 files, if requested via a direct dependency.
+
+            *   `indexstore_directory`: A directory-type `File` that represents
+                the indexstore output files created when the feature
+                `swift.index_while_building` is enabled.
+
+            *   `macro_expansion_directory`: A directory-type `File` that
+                represents the location where macro expansion files were written
+                (only in debug/fastbuild and only when the toolchain supports
+                macros).
     """
 
     # Collect the `SwiftInfo` providers that represent the dependencies of the
@@ -815,20 +826,22 @@ to use swift_common.compile(include_dev_srch_paths = ...) instead.\
         ),
     )
 
-    cc_compilation_outputs = cc_common.create_compilation_outputs(
+    compilation_outputs = cc_common.create_compilation_outputs(
         objects = depset(compile_outputs.object_files),
         pic_objects = depset(compile_outputs.object_files),
     )
 
-    other_compilation_outputs = struct(
-        ast_files = compile_outputs.ast_files,
-        indexstore = compile_outputs.indexstore_directory,
-        macro_expansion_directory = compile_outputs.macro_expansion_directory,
-        const_values_files = compile_outputs.const_values_files,
+    return struct(
+        module_context = module_context,
+        compilation_outputs = compilation_outputs,
+        supplemental_outputs = struct(
+            ast_files = compile_outputs.ast_files,
+            const_values_files = compile_outputs.const_values_files,
+            indexstore_directory = compile_outputs.indexstore_directory,
+            macro_expansion_directory = compile_outputs.macro_expansion_directory,
+        ),
     )
 
-    return module_context, cc_compilation_outputs, other_compilation_outputs
-
 def precompile_clang_module(
         *,
         actions,

swift/internal/feature_names.bzl

@@ -69,6 +69,16 @@ SWIFT_FEATURE_FILE_PREFIX_MAP = "swift.file_prefix_map"
 # graph.
 SWIFT_FEATURE_EMIT_C_MODULE = "swift.emit_c_module"
 
+# If enabled, the compilation action for a target will produce an index store.
+# https://docs.google.com/document/d/1cH2sTpgSnJZCkZtJl1aY-rzy4uGPcrI-6RrUpdATO2Q/
+SWIFT_FEATURE_INDEX_WHILE_BUILDING = "swift.index_while_building"
+
+# If enabled the compilation action will not produce indexes for system modules.
+SWIFT_FEATURE_DISABLE_SYSTEM_INDEX = "swift.disable_system_index"
+
+# Index while building - using a global index store cache
+SWIFT_FEATURE_USE_GLOBAL_INDEX_STORE = "swift.use_global_index_store"
+
 # If enabled, when compiling an explicit C or Objectve-C module, every header
 # included by the module being compiled must belong to one of the modules listed
 # in its dependencies. This is ignored for system modules.
@@ -107,16 +117,6 @@ SWIFT_FEATURE_FULL_DEBUG_INFO = "swift.full_debug_info"
 # Use CodeView debug information, which enables generation of PDBs for debugging.
 SWIFT_FEATURE_CODEVIEW_DEBUG_INFO = "swift.codeview_debug_info"
 
-# If enabled, the compilation action for a target will produce an index store.
-# https://docs.google.com/document/d/1cH2sTpgSnJZCkZtJl1aY-rzy4uGPcrI-6RrUpdATO2Q/
-SWIFT_FEATURE_INDEX_WHILE_BUILDING = "swift.index_while_building"
-
-# If enabled the compilation action will not produce indexes for system modules.
-SWIFT_FEATURE_DISABLE_SYSTEM_INDEX = "swift.disable_system_index"
-
-# Index while building - using a global index store cache
-SWIFT_FEATURE_USE_GLOBAL_INDEX_STORE = "swift.use_global_index_store"
-
 # If enabled, compilation actions and module map generation will assume that the
 # header paths in module maps are relative to the current working directory
 # (i.e., the workspace root); if disabled, header paths in module maps are

swift/internal/output_groups.bzl

@@ -41,8 +41,8 @@ def supplemental_compilation_output_groups(*supplemental_outputs):
             ast_files.extend(outputs.ast_files)
         if outputs.const_values_files:
             const_values_files.extend(outputs.const_values_files)
-        if outputs.indexstore:
-            indexstore_files.append(outputs.indexstore)
+        if outputs.indexstore_directory:
+            indexstore_files.append(outputs.indexstore_directory)
         if outputs.macro_expansion_directory:
             macro_expansions_files.append(outputs.macro_expansion_directory)
 

swift/swift_binary.bzl

@@ -69,9 +69,9 @@ def _swift_binary_impl(ctx):
     )
 
     srcs = ctx.files.srcs
+    output_groups = {}
     module_contexts = []
     additional_linking_contexts = []
-    all_supplemental_outputs = []
 
     # If the binary has sources, compile those first and collect the outputs to
     # be passed to the linker.
@@ -82,7 +82,7 @@ def _swift_binary_impl(ctx):
 
         include_dev_srch_paths = include_developer_search_paths(ctx.attr)
 
-        module_context, cc_compilation_outputs, supplemental_outputs = swift_common.compile(
+        compile_result = swift_common.compile(
             actions = ctx.actions,
             additional_inputs = ctx.files.swiftc_inputs,
             cc_infos = get_providers(ctx.attr.deps, CcInfo),
@@ -104,16 +104,21 @@ def _swift_binary_impl(ctx):
             target_name = ctx.label.name,
             workspace_name = ctx.workspace_name,
         )
+        module_context = compile_result.module_context
         module_contexts.append(module_context)
-        all_supplemental_outputs.append(supplemental_outputs)
+        compilation_outputs = compile_result.compilation_outputs
+        supplemental_outputs = compile_result.supplemental_outputs
+        output_groups = supplemental_compilation_output_groups(
+            supplemental_outputs,
+        )
 
         # Unlike `upstream`, we create a linking_context in order to support
         # `autolink-extract`. See `a1395155c6a27d76aab5e1a93455259a0ac10b2f` and
         # `93219a3b21390f212f5fd013e8db3654fd09814c`.
         linking_context, _ = swift_common.create_linking_context_from_compilation_outputs(
             actions = ctx.actions,
             alwayslink = True,
-            compilation_outputs = cc_compilation_outputs,
+            compilation_outputs = compilation_outputs,
             feature_configuration = feature_configuration,
             include_dev_srch_paths = include_dev_srch_paths,
             label = ctx.label,
@@ -126,8 +131,6 @@ def _swift_binary_impl(ctx):
             swift_toolchain = swift_toolchain,
         )
         additional_linking_contexts.append(linking_context)
-    else:
-        cc_compilation_outputs = cc_common.create_compilation_outputs()
 
     additional_linking_contexts.append(malloc_linking_context(ctx))
 
@@ -172,11 +175,7 @@ def _swift_binary_impl(ctx):
                 files = ctx.files.data,
             ),
         ),
-        OutputGroupInfo(
-            **supplemental_compilation_output_groups(
-                *all_supplemental_outputs
-            )
-        ),
+        OutputGroupInfo(**output_groups),
         swift_common.create_swift_info(
             modules = [
                 swift_common.create_module(

swift/swift_compiler_plugin.bzl

@@ -70,7 +70,7 @@ def _swift_compiler_plugin_impl(ctx):
         module_name = derive_swift_module_name(ctx.label)
     entry_point_function_name = "{}_main".format(module_name)
 
-    module_context, cc_compilation_outputs, supplemental_outputs = swift_common.compile(
+    compile_result = swift_common.compile(
         actions = ctx.actions,
         additional_inputs = ctx.files.swiftc_inputs,
         cc_infos = get_providers(deps, CcInfo),
@@ -103,9 +103,9 @@ def _swift_compiler_plugin_impl(ctx):
         target_name = ctx.label.name,
         workspace_name = ctx.workspace_name,
     )
-    output_groups = supplemental_compilation_output_groups(
-        supplemental_outputs,
-    )
+    module_context = compile_result.module_context
+    compilation_outputs = compile_result.compilation_outputs
+    supplemental_outputs = compile_result.supplemental_outputs
 
     cc_feature_configuration = swift_common.cc_feature_configuration(
         feature_configuration = feature_configuration,
@@ -116,7 +116,7 @@ def _swift_compiler_plugin_impl(ctx):
         additional_inputs = ctx.files.swiftc_inputs,
         additional_linking_contexts = [malloc_linking_context(ctx)],
         cc_feature_configuration = cc_feature_configuration,
-        compilation_outputs = cc_compilation_outputs,
+        compilation_outputs = compilation_outputs,
         deps = deps,
         name = ctx.label.name,
         output_type = "executable",
@@ -141,7 +141,7 @@ def _swift_compiler_plugin_impl(ctx):
             actions = ctx.actions,
             additional_inputs = ctx.files.swiftc_inputs,
             alwayslink = True,
-            compilation_outputs = cc_compilation_outputs,
+            compilation_outputs = compilation_outputs,
             feature_configuration = feature_configuration,
             label = ctx.label,
             include_dev_srch_paths = ctx.attr.testonly,
@@ -166,7 +166,9 @@ def _swift_compiler_plugin_impl(ctx):
                 files = ctx.files.data,
             ),
         ),
-        OutputGroupInfo(**output_groups),
+        OutputGroupInfo(
+            **supplemental_compilation_output_groups(supplemental_outputs)
+        ),
         SwiftCompilerPluginInfo(
             cc_info = CcInfo(
                 compilation_context = module_context.clang.compilation_context,

swift/swift_library.bzl

@@ -183,7 +183,7 @@ def _swift_library_impl(ctx):
 
     include_dev_srch_paths = include_developer_search_paths(ctx.attr)
 
-    module_context, cc_compilation_outputs, supplemental_outputs = swift_common.compile(
+    compile_result = swift_common.compile(
         actions = ctx.actions,
         additional_inputs = additional_inputs,
         cc_infos = get_providers(ctx.attr.deps, CcInfo),
@@ -204,12 +204,16 @@ def _swift_library_impl(ctx):
         workspace_name = ctx.workspace_name,
     )
 
+    module_context = compile_result.module_context
+    compilation_outputs = compile_result.compilation_outputs
+    supplemental_outputs = compile_result.supplemental_outputs
+
     linking_context, linking_output = (
         swift_common.create_linking_context_from_compilation_outputs(
             actions = ctx.actions,
             additional_inputs = additional_inputs,
             alwayslink = ctx.attr.alwayslink,
-            compilation_outputs = cc_compilation_outputs,
+            compilation_outputs = compilation_outputs,
             feature_configuration = feature_configuration,
             include_dev_srch_paths = include_dev_srch_paths,
             label = ctx.label,
@@ -255,9 +259,6 @@ def _swift_library_impl(ctx):
                 files = ctx.files.data,
             ),
         ),
-        OutputGroupInfo(**supplemental_compilation_output_groups(
-            supplemental_outputs,
-        )),
         CcInfo(
             compilation_context = module_context.clang.compilation_context,
             linking_context = linking_context,
@@ -274,6 +275,9 @@ def _swift_library_impl(ctx):
             # not propagate.
             swift_infos = swift_infos,
         ),
+        OutputGroupInfo(
+            **supplemental_compilation_output_groups(supplemental_outputs)
+        ),
     ]
 
     # Propagate an `apple_common.Objc` provider with linking info about the