Ability to explicitly specify output files in apple_core_data_model rule (#2727)

This PR contains one of the two fixes mentioned in #2726. This change
makes it possible to explicitly specify the output files that are
expected to be generated from the provided core data models. This causes
the rule to return a provider containing these individual Swift files
rather than just the containing folder.

Author: daltonclaybrook

apple/internal/resource_actions/datamodel.bzl

@@ -109,6 +109,7 @@ def generate_datamodels(
         datamodel_path,
         input_files,
         output_dir,
+        outputs,
         platform_prerequisites,
         xctoolrunner,
         swift_version = None):
@@ -119,6 +120,7 @@ def generate_datamodels(
         datamodel_path: The path to the directory containing the datamodels.
         input_files: The list of files to process for the given datamodel.
         output_dir: The output directory reference where generated datamodel classes will be.
+        outputs: The list of generated datamodel files or the directory containing those files.
         platform_prerequisites: Struct containing information on the platform being targeted.
         xctoolrunner: A files_to_run for the wrapper around the "xcrun" tool.
         swift_version: (optional) Target Swift version for generated datamodel classes.
@@ -136,9 +138,9 @@ def generate_datamodels(
         args.add("--swift-version", swift_version)
 
     args.add(xctoolrunner_support.prefixed_path(datamodel_path))
-    args.add(xctoolrunner_support.prefixed_path(output_dir.path))
+    args.add(xctoolrunner_support.prefixed_path(output_dir))
 
-    args.add("--xctoolrunner_assert_nonempty_dir", output_dir.path)
+    args.add("--xctoolrunner_assert_nonempty_dir", output_dir)
 
     apple_support.run(
         actions = actions,
@@ -147,6 +149,6 @@ def generate_datamodels(
         executable = xctoolrunner,
         inputs = input_files,
         mnemonic = "MomGenerate",
-        outputs = [output_dir],
+        outputs = outputs,
         xcode_config = platform_prerequisites.xcode_version_config,
     )

apple/internal/resource_rules/apple_core_data_model.bzl

@@ -86,6 +86,7 @@ def _apple_core_data_model_impl(ctx):
         attr = "datamodels",
     )
 
+    expected_outputs = ctx.attr.outs
     output_files = []
     for datamodel_path, files in datamodel_groups.items():
         datamodel_name = paths.replace_extension(
@@ -97,19 +98,30 @@ def _apple_core_data_model_impl(ctx):
             datamodel_name.lower(),
             ctx.label.name,
         )
-        output_dir = actions.declare_directory(dir_name)
+        output_dir_path = "{}/{}/{}".format(ctx.genfiles_dir.path, ctx.label.package, dir_name)
+        expected_file_names = expected_outputs.get(datamodel_name, [])
+        data_model_outputs = []
+        if len(expected_file_names) > 0:
+            for file_name in expected_file_names:
+                file_path = "{}/{}".format(dir_name, file_name)
+                file = actions.declare_file(file_path)
+                data_model_outputs.append(file)
+        else:
+            output_dir = actions.declare_directory(dir_name)
+            data_model_outputs.append(output_dir)
 
         resource_actions.generate_datamodels(
             actions = actions,
             datamodel_path = datamodel_path,
             input_files = files.to_list(),
-            output_dir = output_dir,
+            output_dir = output_dir_path,
+            outputs = data_model_outputs,
             platform_prerequisites = platform_prerequisites,
             swift_version = swift_version,
             xctoolrunner = apple_mac_toolchain_info.xctoolrunner,
         )
 
-        output_files.append(output_dir)
+        output_files.extend(data_model_outputs)
 
     return [DefaultInfo(files = depset(output_files))]
 
@@ -127,12 +139,31 @@ apple_core_data_model = rule(
             "swift_version": attr.string(
                 doc = "Target Swift version for generated classes.",
             ),
+            "outs": attr.string_list_dict(
+                doc = """
+A dictionary where the key is the name of a data model and the value is a
+list of source files expected to be generated from that data model. For
+example, if srcs contains one data model called "Taxonomy.xcdatamodeld" with
+a single entity called "Animal," you might provide this value:
+```
+outs = {
+    "Taxonomy": [
+        "taxonomy+CoreDataModel.swift",
+        "Animal+CoreDataProperties.swift",
+    ],
+},
+```
+If one or more files are provided for a data model, the rule will return these
+files individually as outputs. Otherwise, the rule will return the directory
+containing the sources for the data model.
+""",
+            ),
         },
     ),
     fragments = ["apple"],
     doc = """
-This rule takes a Core Data model definition from a .xcdatamodeld bundle
-and generates Swift or Objective-C source files that can be added as a
-dependency to a swift_library target.
+This rule takes one or more Core Data model definitions from .xcdatamodeld
+bundles and generates Swift or Objective-C source files that can be added
+as srcs of a swift_library target.
 """,
 )

doc/rules-resources.md

@@ -30,12 +30,12 @@ targets (i.e. `apple_resource_bundle` and `apple_resource_group`) through the
 ## apple_core_data_model
 
 <pre>
-apple_core_data_model(<a href="#apple_core_data_model-name">name</a>, <a href="#apple_core_data_model-srcs">srcs</a>, <a href="#apple_core_data_model-swift_version">swift_version</a>)
+apple_core_data_model(<a href="#apple_core_data_model-name">name</a>, <a href="#apple_core_data_model-srcs">srcs</a>, <a href="#apple_core_data_model-outs">outs</a>, <a href="#apple_core_data_model-swift_version">swift_version</a>)
 </pre>
 
-This rule takes a Core Data model definition from a .xcdatamodeld bundle
-and generates Swift or Objective-C source files that can be added as a
-dependency to a swift_library target.
+This rule takes one or more Core Data model definitions from .xcdatamodeld
+bundles and generates Swift or Objective-C source files that can be added
+as srcs of a swift_library target.
 
 **ATTRIBUTES**
 
@@ -44,6 +44,7 @@ dependency to a swift_library target.
 | :------------- | :------------- | :------------- | :------------- | :------------- |
 | <a id="apple_core_data_model-name"></a>name |  A unique name for this target.   | <a href="https://bazel.build/concepts/labels#target-names">Name</a> | required |  |
 | <a id="apple_core_data_model-srcs"></a>srcs |  -   | <a href="https://bazel.build/concepts/labels">List of labels</a> | required |  |
+| <a id="apple_core_data_model-outs"></a>outs |  A dictionary where the key is the name of a data model and the value is a list of source files expected to be generated from that data model. For example, if srcs contains one data model called "Taxonomy.xcdatamodeld" with a single entity called "Animal," you might provide this value: <pre><code>outs = {&#10;    "Taxonomy": [&#10;        "taxonomy+CoreDataModel.swift",&#10;        "Animal+CoreDataProperties.swift",&#10;    ],&#10;},</code></pre> If one or more files are provided for a data model, the rule will return these files individually as outputs. Otherwise, the rule will return the directory containing the sources for the data model.   | <a href="https://bazel.build/rules/lib/dict">Dictionary: String -> List of strings</a> | optional |  `{}`  |
 | <a id="apple_core_data_model-swift_version"></a>swift_version |  Target Swift version for generated classes.   | String | optional |  `""`  |
 
 

test/starlark_tests/apple_core_data_model_tests.bzl

@@ -61,6 +61,17 @@ def apple_core_data_model_test_suite(name):
         tags = [name],
     )
 
+    # Test outputs a list of files rather than directories
+    analysis_target_outputs_test(
+        name = "{}_outputs_explicit_swift_files_test".format(name),
+        target_under_test = "//test/starlark_tests/targets_under_test/apple:explicit_outs_data_model",
+        expected_outputs = [
+            "swift_datamodel.explicit_outs_data_model.coredata.sources/swift_datamodel+CoreDataModel.swift",
+            "swift_datamodel.explicit_outs_data_model.coredata.sources/Item+CoreDataProperties.swift",
+        ],
+        tags = [name],
+    )
+
     # Test registered actions and mnemonics for Obj-C and Swift data models.
     analysis_target_actions_test(
         name = "{}_actions_swift_test".format(name),

test/starlark_tests/targets_under_test/apple/BUILD

@@ -254,6 +254,20 @@ apple_core_data_model(
     tags = common.fixture_tags,
 )
 
+apple_core_data_model(
+    name = "explicit_outs_data_model",
+    srcs = [
+        "//test/starlark_tests/resources:swift_datamodel",
+    ],
+    outs = {
+        "swift_datamodel": [
+            "swift_datamodel+CoreDataModel.swift",
+            "Item+CoreDataProperties.swift",
+        ],
+    },
+    tags = common.fixture_tags,
+)
+
 objc_library(
     name = "fmwk_lib",
     srcs = [