Add a mechanism to provide a list of protocol names for constant valu…

…e extraction. (#1170)

This cherry-picks support for producing const values produced via the
compiler flags `-emit-const-values-path` and
`-const-gather-protocols-file`. rules_apple will start using this
feature in bazelbuild/rules_apple#2418.

---------

Co-authored-by: Tony Allevato <allevato@google.com>
Co-authored-by: Keith Smiley <keithbsmiley@gmail.com>

.bazelci/presubmit.yml

@@ -30,6 +30,12 @@ x_defaults:
       - "//examples/..."
       - "//test/..."
       - "-//examples/apple/..."
+      # The following tests require Swift >5.8.
+      - "-//test:const_values_empty_const_values_multiple_files"
+      - "-//test:const_values_empty_const_values_single_file"
+      - "-//test:const_values_expected_argv"
+      - "-//test:const_values_wmo_single_values_file"
+      - "-//test:output_file_map_default"
   windows_common: &windows_common
     platform: windows
     build_flags:

doc/api.md

@@ -140,6 +140,9 @@ A tuple containing three elements:
           contains the symbol graph data generated by the compiler if the
           `"swift.emit_symbol_graph"` 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.
 
 
 <a id="swift_common.compile_module_interface"></a>
@@ -325,7 +328,8 @@ A tuple of `(CcLinkingContext, CcLinkingOutputs)` containing the linking
 ## swift_common.create_module
 
 <pre>
-swift_common.create_module(<a href="#swift_common.create_module-name">name</a>, <a href="#swift_common.create_module-clang">clang</a>, <a href="#swift_common.create_module-compilation_context">compilation_context</a>, <a href="#swift_common.create_module-is_system">is_system</a>, <a href="#swift_common.create_module-swift">swift</a>)
+swift_common.create_module(<a href="#swift_common.create_module-name">name</a>, <a href="#swift_common.create_module-clang">clang</a>, <a href="#swift_common.create_module-const_gather_protocols">const_gather_protocols</a>, <a href="#swift_common.create_module-compilation_context">compilation_context</a>, <a href="#swift_common.create_module-is_system">is_system</a>,
+                           <a href="#swift_common.create_module-swift">swift</a>)
 </pre>
 
 Creates a value containing Clang/Swift module artifacts of a dependency.
@@ -354,6 +358,7 @@ the set of transitive module names that are propagated by dependencies
 | :------------- | :------------- | :------------- |
 | <a id="swift_common.create_module-name"></a>name |  The name of the module.   |  none |
 | <a id="swift_common.create_module-clang"></a>clang |  A value returned by `swift_common.create_clang_module` that contains artifacts related to Clang modules, such as a module map or precompiled module. This may be `None` if the module is a pure Swift module with no generated Objective-C interface.   |  `None` |
+| <a id="swift_common.create_module-const_gather_protocols"></a>const_gather_protocols |  A list of protocol names from which constant values should be extracted from source code that takes this module as a *direct* dependency.   |  `[]` |
 | <a id="swift_common.create_module-compilation_context"></a>compilation_context |  A value returned from `swift_common.create_compilation_context` that contains the context needed to compile the module being built. This may be `None` if the module wasn't compiled from sources.   |  `None` |
 | <a id="swift_common.create_module-is_system"></a>is_system |  Indicates whether the module is a system module. The default value is `False`. System modules differ slightly from non-system modules in the way that they are passed to the compiler. For example, non-system modules have their Clang module maps passed to the compiler in both implicit and explicit module builds. System modules, on the other hand, do not have their module maps passed to the compiler in implicit module builds because there is currently no way to indicate that modules declared in a file passed via `-fmodule-map-file` should be treated as system modules even if they aren't declared with the `[system]` attribute, and some system modules may not build cleanly with respect to warnings otherwise. Therefore, it is assumed that any module with `is_system == True` must be able to be found using import search paths in order for implicit module builds to succeed.   |  `False` |
 | <a id="swift_common.create_module-swift"></a>swift |  A value returned by `swift_common.create_swift_module` that contains artifacts related to Swift modules, such as the `.swiftmodule`, `.swiftdoc`, and/or `.swiftinterface` files emitted by the compiler. This may be `None` if the module is a pure C/Objective-C module.   |  `None` |
@@ -460,7 +465,7 @@ A provider whose type/layout is an implementation detail and should not
 <pre>
 swift_common.create_swift_module(<a href="#swift_common.create_swift_module-swiftdoc">swiftdoc</a>, <a href="#swift_common.create_swift_module-swiftmodule">swiftmodule</a>, <a href="#swift_common.create_swift_module-ast_files">ast_files</a>, <a href="#swift_common.create_swift_module-defines">defines</a>, <a href="#swift_common.create_swift_module-indexstore">indexstore</a>, <a href="#swift_common.create_swift_module-plugins">plugins</a>,
                                  <a href="#swift_common.create_swift_module-swiftsourceinfo">swiftsourceinfo</a>, <a href="#swift_common.create_swift_module-swiftinterface">swiftinterface</a>, <a href="#swift_common.create_swift_module-private_swiftinterface">private_swiftinterface</a>,
-                                 <a href="#swift_common.create_swift_module-symbol_graph">symbol_graph</a>)
+                                 <a href="#swift_common.create_swift_module-const_protocols_to_gather">const_protocols_to_gather</a>, <a href="#swift_common.create_swift_module-symbol_graph">symbol_graph</a>)
 </pre>
 
 Creates a value representing a Swift module use as a Swift dependency.
@@ -479,6 +484,7 @@ Creates a value representing a Swift module use as a Swift dependency.
 | <a id="swift_common.create_swift_module-swiftsourceinfo"></a>swiftsourceinfo |  The `.swiftsourceinfo` file emitted by the compiler for this module. May be `None` if no source info file was emitted.   |  `None` |
 | <a id="swift_common.create_swift_module-swiftinterface"></a>swiftinterface |  The `.swiftinterface` file emitted by the compiler for this module. May be `None` if no module interface file was emitted.   |  `None` |
 | <a id="swift_common.create_swift_module-private_swiftinterface"></a>private_swiftinterface |  The `.private.swiftinterface` file emitted by the compiler for this module. May be `None` if no private module interface file was emitted.   |  `None` |
+| <a id="swift_common.create_swift_module-const_protocols_to_gather"></a>const_protocols_to_gather |  A list of protocol names from which constant values should be extracted from source code that takes this module as a *direct* dependency.   |  `[]` |
 | <a id="swift_common.create_swift_module-symbol_graph"></a>symbol_graph |  A `File` representing the directory that contains the symbol graph data generated by the compiler if the `"swift.emit_symbol_graph"` feature is enabled, otherwise this will be `None`.   |  `None` |
 
 **RETURNS**

doc/providers.md

@@ -84,11 +84,11 @@ Propagates Swift-specific information about a `proto_library`.
 ## SwiftToolchainInfo
 
 <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-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>)
+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>)
 </pre>
 
 Propagates information about a Swift toolchain to compilation and linking rules
@@ -102,6 +102,7 @@ that use the toolchain.
 | <a id="SwiftToolchainInfo-action_configs"></a>action_configs |  This field is an internal implementation detail of the build rules.    |
 | <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-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.    |