Initial support for code coverage. (#505)

* `kt_jvm_test` supports coverage collection.
* `kt_jvm_library` propagates transitive coverage information.

This provides coverage support of Java code in `java_library` + `android_library` targets through `kt_jvm_test.`

It also provides coverage support of Java code in `kt_jvm_library` when experimental_use_abi_jars is enabled.

TODO: Instrument Kotlin code for coverage.

kotlin/internal/jvm/compile.bzl

@@ -617,8 +617,17 @@ def kt_jvm_produce_jar_actions(ctx, rule_kind):
         exports = [_java_info(d) for d in getattr(ctx.attr, "exports", [])],
         neverlink = getattr(ctx.attr, "neverlink", False),
     )
+
+    instrumented_files = coverage_common.instrumented_files_info(
+        ctx,
+        source_attributes = ["srcs"],
+        dependency_attributes = ["deps", "exports", "associates", "friends"],
+        extensions = ["kt", "java"],
+    )
+
     return struct(
         java = java_info,
+        instrumented_files = instrumented_files,
         kt = _KtJvmInfo(
             srcs = ctx.files.srcs,
             module_name = associates.module_name,
@@ -891,4 +900,10 @@ def export_only_providers(ctx, actions, attr, outputs):
                 getattr(attr, "exports", []),
             ),
         ),
+        instrumented_files = coverage_common.instrumented_files_info(
+            ctx,
+            source_attributes = ["srcs"],
+            dependency_attributes = ["deps", "exports", "associates", "friends"],
+            extensions = ["kt", "java"],
+        )
     )

kotlin/internal/jvm/impl.bzl

@@ -20,6 +20,7 @@ load(
     "//kotlin/internal:defs.bzl",
     _KtCompilerPluginInfo = "KtCompilerPluginInfo",
     _KtJvmInfo = "KtJvmInfo",
+    _TOOLCHAIN_TYPE = "TOOLCHAIN_TYPE",
 )
 load(
     "//kotlin/internal/utils:utils.bzl",
@@ -34,6 +35,7 @@ def _make_providers(ctx, providers, transitive_files = depset(order = "default")
         providers = [
             providers.java,
             providers.kt,
+            providers.instrumented_files,
             DefaultInfo(
                 files = depset([ctx.outputs.jar, ctx.outputs.jdeps]),
                 runfiles = ctx.runfiles(
@@ -56,11 +58,69 @@ def _write_launcher_action(ctx, rjars, main_class, jvm_flags, args = "", wrapper
         jvm_flags: The flags that should be passed to the jvm.
         args: Args that should be passed to the Binary.
     """
-    classpath = ":".join(["${RUNPATH}%s" % (j.short_path) for j in rjars.to_list()])
     jvm_flags = " ".join([ctx.expand_location(f, ctx.attr.data) for f in jvm_flags])
     template = ctx.attr._java_stub_template.files.to_list()[0]
     java_bin_path = ctx.attr._java_runtime[java_common.JavaRuntimeInfo].java_executable_exec_path
 
+    if ctx.configuration.coverage_enabled:
+        jacocorunner = ctx.toolchains[_TOOLCHAIN_TYPE].jacocorunner
+        classpath = ctx.configuration.host_path_separator.join(
+            ["${RUNPATH}%s" % (j.short_path) for j in rjars.to_list() + jacocorunner.files.to_list()],
+        )
+        jacoco_metadata_file = ctx.actions.declare_file(
+            "%s.jacoco_metadata.txt" % ctx.attr.name,
+            sibling = ctx.outputs.executable,
+        )
+        ctx.actions.write(jacoco_metadata_file, "\n".join([
+            jar.short_path.replace("../", "external/")
+            for jar in rjars.to_list()
+        ]))
+        ctx.actions.expand_template(
+            template = template,
+            output = ctx.outputs.executable,
+            substitutions = {
+                "%classpath%": classpath,
+                "%runfiles_manifest_only%": "",
+                "%java_start_class%": "com.google.testing.coverage.JacocoCoverageRunner",
+                "%javabin%": "JAVABIN=" + java_bin_path,
+                "%jvm_flags%": jvm_flags,
+                "%set_jacoco_metadata%": "export JACOCO_METADATA_JAR=\"$JAVA_RUNFILES/{}/{}\"".format(ctx.workspace_name, jacoco_metadata_file.short_path),
+                "%set_jacoco_main_class%": """export JACOCO_MAIN_CLASS={}""".format(main_class),
+                "%set_jacoco_java_runfiles_root%": """export JACOCO_JAVA_RUNFILES_ROOT=$JAVA_RUNFILES/{}/""".format(ctx.workspace_name),
+                "%set_java_coverage_new_implementation%": """export JAVA_COVERAGE_NEW_IMPLEMENTATION=YES""",
+                "%workspace_prefix%": ctx.workspace_name + "/",
+                "%test_runtime_classpath_file%": "export TEST_RUNTIME_CLASSPATH_FILE=${JAVA_RUNFILES}",
+                "%needs_runfiles%": "0" if paths.is_absolute(java_bin_path) else "1"
+            },
+            is_executable = True,
+        )
+        return [jacoco_metadata_file]
+
+    else:
+        classpath = ctx.configuration.host_path_separator.join(
+            ["${RUNPATH}%s" % (j.short_path) for j in rjars.to_list()],
+        )
+        ctx.actions.expand_template(
+            template = template,
+            output = ctx.outputs.executable,
+            substitutions = {
+                "%classpath%": classpath,
+                "%runfiles_manifest_only%": "",
+                "%java_start_class%": main_class,
+                "%javabin%": "JAVABIN=" + java_bin_path,
+                "%jvm_flags%": jvm_flags,
+                "%set_jacoco_metadata%": "",
+                "%set_jacoco_main_class%": "",
+                "%set_jacoco_java_runfiles_root%": "",
+                "%set_java_coverage_new_implementation%": """export JAVA_COVERAGE_NEW_IMPLEMENTATION=NO""",
+                "%workspace_prefix%": ctx.workspace_name + "/",
+                "%test_runtime_classpath_file%": "export TEST_RUNTIME_CLASSPATH_FILE=${JAVA_RUNFILES}",
+                "%needs_runfiles%": "0" if paths.is_absolute(java_bin_path) else "1"
+            },
+            is_executable = True,
+        )
+        return []
+
     ctx.actions.expand_template(
         template = template,
         output = ctx.outputs.executable,
@@ -211,6 +271,11 @@ def kt_jvm_junit_test_impl(ctx):
     providers = _kt_jvm_produce_jar_actions(ctx, "kt_jvm_test")
     runtime_jars = depset(ctx.files._bazel_test_runner, transitive = [providers.java.transitive_runtime_jars])
 
+    coverage_runfiles = []
+    if ctx.configuration.coverage_enabled:
+        jacocorunner = ctx.toolchains[_TOOLCHAIN_TYPE].jacocorunner
+        coverage_runfiles = jacocorunner.files.to_list()
+
     test_class = ctx.attr.test_class
 
     # If no test_class, do a best-effort attempt to infer one.
@@ -223,7 +288,7 @@ def kt_jvm_junit_test_impl(ctx):
                         test_class = elements[1].split(".")[0].replace("/", ".")
                         break
 
-    _write_launcher_action(
+    coverage_metadata = _write_launcher_action(
         ctx,
         runtime_jars,
         main_class = ctx.attr.main_class,
@@ -238,7 +303,7 @@ def kt_jvm_junit_test_impl(ctx):
         providers,
         depset(
             order = "default",
-            transitive = [runtime_jars],
+            transitive = [runtime_jars, depset(coverage_runfiles), depset(coverage_metadata)],
             direct = ctx.files._java_runtime,
         ),
         # adds common test variables, including TEST_WORKSPACE.

kotlin/internal/jvm/jvm.bzl

@@ -349,6 +349,9 @@ kt_jvm_test = rule(
             default = "",
         ),
         "main_class": attr.string(default = "com.google.testing.junit.runner.BazelTestRunner"),
+        "_lcov_merger": attr.label(
+            default = Label("@bazel_tools//tools/test/CoverageOutputGenerator/java/com/google/devtools/coverageoutputgenerator:Main"),
+        ),
     }),
     executable = True,
     outputs = _common_outputs,

kotlin/internal/toolchains.bzl

@@ -91,6 +91,7 @@ def _kotlin_toolchain_impl(ctx):
         kotlinc_options = ctx.attr.kotlinc_options[KotlincOptions] if ctx.attr.kotlinc_options else None,
         empty_jar = ctx.file._empty_jar,
         empty_jdeps = ctx.file._empty_jdeps,
+        jacocorunner = ctx.attr.jacocorunner
     )
 
     return [
@@ -248,6 +249,9 @@ _kt_toolchain = rule(
             cfg = "target",
             default = Label("//third_party:empty.jdeps"),
         ),
+        "jacocorunner": attr.label(
+            default = Label("@bazel_tools//tools/jdk:JacocoCoverage"),
+        ),
     },
     implementation = _kotlin_toolchain_impl,
     provides = [platform_common.ToolchainInfo],
@@ -268,7 +272,8 @@ def define_kt_toolchain(
         experimental_reduce_classpath_mode = None,
         experimental_multiplex_workers = None,
         javac_options = None,
-        kotlinc_options = None):
+        kotlinc_options = None,
+        jacocorunner = None):
     """Define the Kotlin toolchain."""
     impl_name = name + "_impl"
 
@@ -298,6 +303,7 @@ def define_kt_toolchain(
         javac_options = javac_options,
         kotlinc_options = kotlinc_options,
         visibility = ["//visibility:public"],
+        jacocorunner = jacocorunner,
     )
     native.toolchain(
         name = name,