Support swift_{binary,test} generating a .dSYM bundle as an output when --apple_generate_dsym is set

doc/providers.md

@@ -84,10 +84,11 @@ Propagates Swift-specific information about a `proto_library`.
 
 <pre>
 SwiftToolchainInfo(<a href="#SwiftToolchainInfo-action_configs">action_configs</a>, <a href="#SwiftToolchainInfo-cc_toolchain_info">cc_toolchain_info</a>, <a href="#SwiftToolchainInfo-clang_implicit_deps_providers">clang_implicit_deps_providers</a>,
-                   <a href="#SwiftToolchainInfo-const_protocols_to_gather">const_protocols_to_gather</a>, <a href="#SwiftToolchainInfo-developer_dirs">developer_dirs</a>, <a href="#SwiftToolchainInfo-entry_point_linkopts_provider">entry_point_linkopts_provider</a>,
-                   <a href="#SwiftToolchainInfo-feature_allowlists">feature_allowlists</a>, <a href="#SwiftToolchainInfo-generated_header_module_implicit_deps_providers">generated_header_module_implicit_deps_providers</a>,
-                   <a href="#SwiftToolchainInfo-implicit_deps_providers">implicit_deps_providers</a>, <a href="#SwiftToolchainInfo-package_configurations">package_configurations</a>, <a href="#SwiftToolchainInfo-requested_features">requested_features</a>, <a href="#SwiftToolchainInfo-root_dir">root_dir</a>,
-                   <a href="#SwiftToolchainInfo-swift_worker">swift_worker</a>, <a href="#SwiftToolchainInfo-test_configuration">test_configuration</a>, <a href="#SwiftToolchainInfo-tool_configs">tool_configs</a>, <a href="#SwiftToolchainInfo-unsupported_features">unsupported_features</a>)
+                   <a href="#SwiftToolchainInfo-const_protocols_to_gather">const_protocols_to_gather</a>, <a href="#SwiftToolchainInfo-debug_outputs_provider">debug_outputs_provider</a>, <a href="#SwiftToolchainInfo-developer_dirs">developer_dirs</a>,
+                   <a href="#SwiftToolchainInfo-entry_point_linkopts_provider">entry_point_linkopts_provider</a>, <a href="#SwiftToolchainInfo-feature_allowlists">feature_allowlists</a>,
+                   <a href="#SwiftToolchainInfo-generated_header_module_implicit_deps_providers">generated_header_module_implicit_deps_providers</a>, <a href="#SwiftToolchainInfo-implicit_deps_providers">implicit_deps_providers</a>,
+                   <a href="#SwiftToolchainInfo-package_configurations">package_configurations</a>, <a href="#SwiftToolchainInfo-requested_features">requested_features</a>, <a href="#SwiftToolchainInfo-root_dir">root_dir</a>, <a href="#SwiftToolchainInfo-swift_worker">swift_worker</a>,
+                   <a href="#SwiftToolchainInfo-test_configuration">test_configuration</a>, <a href="#SwiftToolchainInfo-tool_configs">tool_configs</a>, <a href="#SwiftToolchainInfo-unsupported_features">unsupported_features</a>)
 </pre>
 
 Propagates information about a Swift toolchain to compilation and linking rules
@@ -102,6 +103,7 @@ that use the toolchain.
 | <a id="SwiftToolchainInfo-cc_toolchain_info"></a>cc_toolchain_info |  The `cc_common.CcToolchainInfo` provider from the Bazel C++ toolchain that this Swift toolchain depends on.    |
 | <a id="SwiftToolchainInfo-clang_implicit_deps_providers"></a>clang_implicit_deps_providers |  A `struct` with the following fields, which represent providers from targets that should be added as implicit dependencies of any precompiled explicit C/Objective-C modules:<br><br>*   `cc_infos`: A list of `CcInfo` providers from targets specified as the     toolchain's implicit dependencies. *   `objc_infos`: A list of `apple_common.Objc` providers from targets specified     as the toolchain's implicit dependencies. *   `swift_infos`: A list of `SwiftInfo` providers from targets specified as the     toolchain's implicit dependencies.<br><br>For ease of use, this field is never `None`; it will always be a valid `struct` containing the fields described above, even if those lists are empty.    |
 | <a id="SwiftToolchainInfo-const_protocols_to_gather"></a>const_protocols_to_gather |  `File`. A JSON file specifying a list of protocols for extraction of conformances' const values.    |
+| <a id="SwiftToolchainInfo-debug_outputs_provider"></a>debug_outputs_provider |  An optional function that provides toolchain-specific logic around the handling of additional debug outputs for `swift_binary` and `swift_test` targets. If specified, this function must take the following keyword arguments: *   `ctx`: The rule context of the calling binary or test rule. It must return a `struct` with the following fields: *   `additional_outputs`: Additional outputs expected from the linking action. *   `variables_extension`: A dictionary of additional crosstool variables to     pass to the linking action.    |
 | <a id="SwiftToolchainInfo-developer_dirs"></a>developer_dirs |  A list of `structs` containing the following fields:*   `developer_path_label`: A `string` representing the type of developer path. *   `path`: A `string` representing the path to the developer framework.    |
 | <a id="SwiftToolchainInfo-entry_point_linkopts_provider"></a>entry_point_linkopts_provider |  A function that returns flags that should be passed to the linker to control the name of the entry point of a linked binary for rules that customize their entry point. This function must take the following keyword arguments: *   `entry_point_name`: The name of the entry point function, as was passed to     the Swift compiler using the `-entry-point-function-name` flag. It must return a `struct` with the following fields: *   `linkopts`: A list of strings that will be passed as additional linker flags     when linking a binary with a custom entry point.    |
 | <a id="SwiftToolchainInfo-feature_allowlists"></a>feature_allowlists |  A list of `SwiftFeatureAllowlistInfo` providers that allow or prohibit packages from requesting or disabling features.    |

swift/internal/linking.bzl

@@ -568,19 +568,22 @@ def new_objc_provider(
     return apple_common.new_objc_provider(**kwargs)
 
 def register_link_binary_action(
+        *,
         actions,
-        additional_inputs,
-        additional_linking_contexts,
+        additional_inputs = [],
+        additional_linking_contexts = [],
+        additional_outputs = [],
         compilation_outputs,
         deps,
         feature_configuration,
         name,
-        module_contexts,
+        module_contexts = [],
         output_type,
         owner,
         stamp,
         swift_toolchain,
-        user_link_flags):
+        user_link_flags = [],
+        variables_extension = {}):
     """Registers an action that invokes the linker to produce a binary.
 
     Args:
@@ -590,6 +593,8 @@ def register_link_binary_action(
             scripts, and so forth.
         additional_linking_contexts: Additional linking contexts that provide
             libraries or flags that should be linked into the executable.
+        additional_outputs: Additional files that are outputs of the linking
+            action but which are not among the return value of `cc_common.link`.
         compilation_outputs: A `CcCompilationOutputs` object containing object
             files that will be passed to the linker.
         deps: A list of targets representing additional libraries that will be
@@ -611,6 +616,8 @@ def register_link_binary_action(
         user_link_flags: Additional flags passed to the linker. Any
             `$(location ...)` placeholders are assumed to have already been
             expanded.
+        variables_extension: A dictionary containing additional crosstool
+            variables that should be set for the linking action.
 
     Returns:
         A `CcLinkingOutputs` object that contains the `executable` or
@@ -749,6 +756,7 @@ def register_link_binary_action(
     return cc_common.link(
         actions = actions,
         additional_inputs = additional_inputs,
+        additional_outputs = additional_outputs,
         cc_toolchain = swift_toolchain.cc_toolchain_info,
         compilation_outputs = compilation_outputs,
         feature_configuration = get_cc_feature_configuration(
@@ -760,4 +768,5 @@ def register_link_binary_action(
         link_deps_statically = True,
         output_type = output_type,
         stamp = stamp,
+        variables_extension = variables_extension,
     )

swift/providers.bzl

@@ -223,6 +223,16 @@ containing the fields described above, even if those lists are empty.
         "const_protocols_to_gather": """\
 `File`. A JSON file specifying a list of protocols for extraction of
 conformances' const values.
+""",
+        "debug_outputs_provider": """\
+An optional function that provides toolchain-specific logic around the handling
+of additional debug outputs for `swift_binary` and `swift_test` targets.
+If specified, this function must take the following keyword arguments:
+*   `ctx`: The rule context of the calling binary or test rule.
+It must return a `struct` with the following fields:
+*   `additional_outputs`: Additional outputs expected from the linking action.
+*   `variables_extension`: A dictionary of additional crosstool variables to
+    pass to the linking action.
 """,
         "developer_dirs": """
 A list of `structs` containing the following fields:\

swift/swift_binary.bzl

@@ -116,6 +116,17 @@ def _swift_binary_impl(ctx):
 
     additional_linking_contexts.append(malloc_linking_context(ctx))
 
+    # Apply the optional debugging outputs extension if the toolchain defines
+    # one.
+    debug_outputs_provider = swift_toolchain.debug_outputs_provider
+    if debug_outputs_provider:
+        debug_extension = debug_outputs_provider(ctx = ctx)
+        additional_debug_outputs = debug_extension.additional_outputs
+        variables_extension = debug_extension.variables_extension
+    else:
+        additional_debug_outputs = []
+        variables_extension = {}
+
     if swift_common.is_enabled(
         feature_configuration = feature_configuration,
         feature_name = SWIFT_FEATURE_ADD_TARGET_NAME_TO_OUTPUT,
@@ -128,6 +139,7 @@ def _swift_binary_impl(ctx):
         actions = ctx.actions,
         additional_inputs = ctx.files.swiftc_inputs,
         additional_linking_contexts = additional_linking_contexts,
+        additional_outputs = additional_debug_outputs,
         feature_configuration = feature_configuration,
         compilation_outputs = compilation_outputs,
         deps = ctx.attr.deps,
@@ -142,11 +154,15 @@ def _swift_binary_impl(ctx):
             ctx.attr.linkopts,
             ctx.attr.swiftc_inputs,
         ) + ctx.fragments.cpp.linkopts,
+        variables_extension = variables_extension,
     )
 
     return [
         DefaultInfo(
             executable = linking_outputs.executable,
+            files = depset(
+                [linking_outputs.executable] + additional_debug_outputs,
+            ),
             runfiles = ctx.runfiles(
                 collect_data = True,
                 collect_default = True,

swift/swift_test.bzl

@@ -494,6 +494,17 @@ def _swift_test_impl(ctx):
     # Mach-O type `MH_BUNDLE` instead of `MH_EXECUTE`.
     extra_linkopts = ["-Wl,-bundle"] if is_bundled else []
 
+    # Apply the optional debugging outputs extension if the toolchain defines
+    # one.
+    debug_outputs_provider = swift_toolchain.debug_outputs_provider
+    if debug_outputs_provider:
+        debug_extension = debug_outputs_provider(ctx = ctx)
+        additional_debug_outputs = debug_extension.additional_outputs
+        variables_extension = debug_extension.variables_extension
+    else:
+        additional_debug_outputs = []
+        variables_extension = {}
+
     if swift_common.is_enabled(
         feature_configuration = feature_configuration,
         feature_name = SWIFT_FEATURE_ADD_TARGET_NAME_TO_OUTPUT,
@@ -506,6 +517,7 @@ def _swift_test_impl(ctx):
         actions = ctx.actions,
         additional_inputs = ctx.files.swiftc_inputs,
         additional_linking_contexts = additional_linking_contexts,
+        additional_outputs = additional_debug_outputs,
         compilation_outputs = compilation_outputs,
         deps = all_deps,
         feature_configuration = feature_configuration,
@@ -520,6 +532,7 @@ def _swift_test_impl(ctx):
             ctx.attr.linkopts,
             ctx.attr.swiftc_inputs,
         ) + extra_linkopts + ctx.fragments.cpp.linkopts,
+        variables_extension = variables_extension,
     )
 
     # If the tests are to be bundled, create the bundle and the test runner
@@ -552,7 +565,10 @@ def _swift_test_impl(ctx):
     return [
         DefaultInfo(
             executable = executable,
-            files = depset(direct = [executable] + additional_test_outputs),
+            files = depset(
+                [executable] + additional_test_outputs +
+                additional_debug_outputs,
+            ),
             runfiles = ctx.runfiles(
                 collect_data = True,
                 collect_default = True,

swift/toolchains/swift_toolchain.bzl

@@ -519,6 +519,7 @@ def _swift_toolchain_impl(ctx):
         clang_implicit_deps_providers = (
             collect_implicit_deps_providers([])
         ),
+        debug_outputs_provider = None,
         developer_dirs = [],
         entry_point_linkopts_provider = _entry_point_linkopts_provider,
         feature_allowlists = [

swift/toolchains/xcode_swift_toolchain.bzl

@@ -630,6 +630,25 @@ def _entry_point_linkopts_provider(*, entry_point_name):
         linkopts = ["-Wl,-alias,_{},_main".format(entry_point_name)],
     )
 
+def _dsym_provider(*, ctx):
+    """Apple-specific linking extension to generate .dSYM binaries.
+
+    This extension generates a minimal dSYM bundle that LLDB can find next to
+    the built binary.
+    """
+    dsym_file = ctx.actions.declare_file(
+        "{name}.dSYM/Contents/Resources/DWARF/{name}".format(
+            name = ctx.label.name,
+        ),
+    )
+    variables_extension = {
+        "dsym_path": dsym_file.path,
+    }
+    return struct(
+        additional_outputs = [dsym_file],
+        variables_extension = variables_extension,
+    )
+
 def _xcode_swift_toolchain_impl(ctx):
     cpp_fragment = ctx.fragments.cpp
     apple_toolchain = apple_common.apple_toolchain()
@@ -778,6 +797,11 @@ def _xcode_swift_toolchain_impl(ctx):
             target[SwiftFeatureAllowlistInfo]
             for target in ctx.attr.feature_allowlists
         ],
+        debug_outputs_provider = (
+            # This function unconditionally declares the output file, so we
+            # should only use it if a .dSYM is being requested during the build.
+            _dsym_provider if cpp_fragment.apple_generate_dsym else None
+        ),
         generated_header_module_implicit_deps_providers = (
             collect_implicit_deps_providers(
                 ctx.attr.generated_header_module_implicit_deps,