Add current api check as validation for from-text stub generation

Currently, there is no build action ensuring that the API text files are
up to date, unless a user runs `m checkapi` or `m update-api`. This
means that the user must run `m update-api` after making a change that
modifies api surface(s), so that the API text file reflects the local
change. This adds additional layer of action to developers, and it is
not guaranteed that the developer will always run `m update-api` after
making an api surface-affecting changes.

To prevent such mistake, this change adds droidstub-level api check as
validation for from-text stub generation. With this change, the build
will fail if the API text file is not up to date and the user must run
`m update-api` when making api surface-affecting local changes.

The validation is done by adding all droidstubs modules associated with
the java_api_contributions passed to java_api_library via
`api_contributions` as dependency and setting the current api timestamp
files as the validations for the from-text stubs generating build rule.

The full api surface libraries will not run the validations to avoid
circular dependency. However, all java_sdk_library generated
java_api_library modules will run validations, mapped to the droidstubs
in the same api domaion.

If the user sets the environment variable `DISABLE_STUB_VALIDATION=true`, validation
actions are not run. Validation actions run by default.

Test: m nothing --build-from-text-stub and run ninja query to verify `check_current_api.timestamp`s are listed as validation \
      DISABLE_STUB_VALIDATION=true m nothing --build-from-text-stub and run ninja query to verify that validation actions are not added
Bug: 288624417
Change-Id: I329e6438fe8f3ac30d8c6a971d57853ed6b0d150
diff --git a/java/core-libraries/Android.bp b/java/core-libraries/Android.bp
index 4380f4f..8b7387a 100644
--- a/java/core-libraries/Android.bp
+++ b/java/core-libraries/Android.bp
@@ -66,6 +66,7 @@
     libs: [
         "stub-annotations",
     ],
+    enable_validation: false,
 }
 
 java_library {
diff --git a/java/droidstubs.go b/java/droidstubs.go
index 5432ce7..8ab2f2a 100644
--- a/java/droidstubs.go
+++ b/java/droidstubs.go
@@ -171,6 +171,10 @@
 	ApiStubsSrcProvider
 }
 
+type currentApiTimestampProvider interface {
+	CurrentApiTimestamp() android.Path
+}
+
 // droidstubs passes sources files through Metalava to generate stub .java files that only contain the API to be
 // documented, filtering out hidden classes and methods.  The resulting .java files are intended to be passed to
 // a droiddoc module to generate documentation.
@@ -238,10 +242,15 @@
 	return d.stubsSrcJar
 }
 
+func (d *Droidstubs) CurrentApiTimestamp() android.Path {
+	return d.checkCurrentApiTimestamp
+}
+
 var metalavaMergeAnnotationsDirTag = dependencyTag{name: "metalava-merge-annotations-dir"}
 var metalavaMergeInclusionAnnotationsDirTag = dependencyTag{name: "metalava-merge-inclusion-annotations-dir"}
 var metalavaAPILevelsAnnotationsDirTag = dependencyTag{name: "metalava-api-levels-annotations-dir"}
 var metalavaAPILevelsModuleTag = dependencyTag{name: "metalava-api-levels-module-tag"}
+var metalavaCurrentApiTimestampTag = dependencyTag{name: "metalava-current-api-timestamp-tag"}
 
 func (d *Droidstubs) DepsMutator(ctx android.BottomUpMutatorContext) {
 	d.Javadoc.addDeps(ctx)
diff --git a/java/droidstubs_test.go b/java/droidstubs_test.go
index e149b98..f86e1ac 100644
--- a/java/droidstubs_test.go
+++ b/java/droidstubs_test.go
@@ -392,7 +392,7 @@
 						removed_api_file: "A/removed.txt",
 					}
 				},
-				visibility: ["//a"],
+				visibility: ["//a", "//b"],
 			}
 		`,
 		map[string][]byte{
diff --git a/java/java.go b/java/java.go
index 35fd7c2..1cb7943 100644
--- a/java/java.go
+++ b/java/java.go
@@ -1664,6 +1664,8 @@
 	extractedSrcJar           android.WritablePath
 	// .dex of stubs, used for hiddenapi processing
 	dexJarFile OptionalDexJarPath
+
+	validationPaths android.Paths
 }
 
 type JavaApiLibraryProperties struct {
@@ -1699,6 +1701,12 @@
 	// The jar will also be passed to metalava as a classpath to
 	// generate compilable stubs.
 	System_modules *string
+
+	// If true, the module runs validation on the API signature files provided
+	// by the modules passed via api_contributions by checking if the files are
+	// in sync with the source Java files. However, the environment variable
+	// DISABLE_STUB_VALIDATION has precedence over this property.
+	Enable_validation *bool
 }
 
 func ApiLibraryFactory() android.Module {
@@ -1787,6 +1795,12 @@
 	}
 }
 
+func (al *ApiLibrary) addValidation(ctx android.ModuleContext, cmd *android.RuleBuilderCommand, validationPaths android.Paths) {
+	for _, validationPath := range validationPaths {
+		cmd.Validation(validationPath)
+	}
+}
+
 // This method extracts the stub class files from the stub jar file provided
 // from full_api_surface_stub module instead of compiling the srcjar generated from invoking metalava.
 // This method is used because metalava can generate compilable from-text stubs only when
@@ -1823,8 +1837,28 @@
 
 func (al *ApiLibrary) DepsMutator(ctx android.BottomUpMutatorContext) {
 	apiContributions := al.properties.Api_contributions
+	addValidations := !ctx.Config().IsEnvTrue("DISABLE_STUB_VALIDATION") &&
+		proptools.BoolDefault(al.properties.Enable_validation, true)
 	for _, apiContributionName := range apiContributions {
 		ctx.AddDependency(ctx.Module(), javaApiContributionTag, apiContributionName)
+
+		// Add the java_api_contribution module generating droidstubs module
+		// as dependency when validation adding conditions are met and
+		// the java_api_contribution module name has ".api.contribution" suffix.
+		// All droidstubs-generated modules possess the suffix in the name,
+		// but there is no such guarantee for tests.
+		if addValidations {
+			if strings.HasSuffix(apiContributionName, ".api.contribution") {
+				ctx.AddDependency(ctx.Module(), metalavaCurrentApiTimestampTag, strings.TrimSuffix(apiContributionName, ".api.contribution"))
+			} else {
+				ctx.ModuleErrorf("Validation is enabled for module %s but a "+
+					"current timestamp provider is not found for the api "+
+					"contribution %s",
+					ctx.ModuleName(),
+					apiContributionName,
+				)
+			}
+		}
 	}
 	ctx.AddVariationDependencies(nil, libTag, al.properties.Libs...)
 	ctx.AddVariationDependencies(nil, staticLibTag, al.properties.Static_libs...)
@@ -1862,8 +1896,7 @@
 		android.PathForModuleOut(ctx, "metalava.sbox.textproto")).
 		SandboxInputs()
 
-	var stubsDir android.OptionalPath
-	stubsDir = android.OptionalPathForPath(android.PathForModuleOut(ctx, "metalava", "stubsDir"))
+	stubsDir := android.OptionalPathForPath(android.PathForModuleOut(ctx, "metalava", "stubsDir"))
 	rule.Command().Text("rm -rf").Text(stubsDir.String())
 	rule.Command().Text("mkdir -p").Text(stubsDir.String())
 
@@ -1895,6 +1928,10 @@
 		case systemModulesTag:
 			module := dep.(SystemModulesProvider)
 			systemModulesPaths = append(systemModulesPaths, module.HeaderJars()...)
+		case metalavaCurrentApiTimestampTag:
+			if currentApiTimestampProvider, ok := dep.(currentApiTimestampProvider); ok {
+				al.validationPaths = append(al.validationPaths, currentApiTimestampProvider.CurrentApiTimestamp())
+			}
 		}
 	})
 
@@ -1918,6 +1955,8 @@
 		cmd.FlagWithInput("--migrate-nullness ", previousApi)
 	}
 
+	al.addValidation(ctx, cmd, al.validationPaths)
+
 	al.stubsSrcJar = android.PathForModuleOut(ctx, "metalava", ctx.ModuleName()+"-"+"stubs.srcjar")
 	al.stubsJarWithoutStaticLibs = android.PathForModuleOut(ctx, "metalava", "stubs.jar")
 	al.stubsJar = android.PathForModuleOut(ctx, ctx.ModuleName(), fmt.Sprintf("%s.jar", ctx.ModuleName()))
diff --git a/java/java_test.go b/java/java_test.go
index 6b8b735..c4fc55b 100644
--- a/java/java_test.go
+++ b/java/java_test.go
@@ -1847,9 +1847,17 @@
 }
 
 func TestJavaApiContributionEmptyApiFile(t *testing.T) {
-	testJavaError(t,
+	android.GroupFixturePreparers(
+		prepareForJavaTest,
+		android.FixtureMergeEnv(
+			map[string]string{
+				"DISABLE_STUB_VALIDATION": "true",
+			},
+		),
+	).ExtendWithErrorHandler(android.FixtureExpectsAtLeastOneErrorMatchingPattern(
 		"Error: foo has an empty api file.",
-		`java_api_contribution {
+	)).RunTestWithBp(t, `
+		java_api_contribution {
 			name: "foo",
 		}
 		java_api_library {
@@ -1874,7 +1882,20 @@
 		api_surface: "public",
 	}
 	`
-	ctx, _ := testJavaWithFS(t, `
+	ctx := android.GroupFixturePreparers(
+		prepareForJavaTest,
+		android.FixtureMergeMockFs(
+			map[string][]byte{
+				"a/Android.bp": []byte(provider_bp_a),
+				"b/Android.bp": []byte(provider_bp_b),
+			},
+		),
+		android.FixtureMergeEnv(
+			map[string]string{
+				"DISABLE_STUB_VALIDATION": "true",
+			},
+		),
+	).RunTestWithBp(t, `
 		java_api_library {
 			name: "bar1",
 			api_surface: "public",
@@ -1886,11 +1907,7 @@
 			api_surface: "system",
 			api_contributions: ["foo1", "foo2"],
 		}
-		`,
-		map[string][]byte{
-			"a/Android.bp": []byte(provider_bp_a),
-			"b/Android.bp": []byte(provider_bp_b),
-		})
+	`)
 
 	testcases := []struct {
 		moduleName         string
@@ -1944,7 +1961,22 @@
 		api_surface: "system",
 	}
 	`
-	ctx, _ := testJavaWithFS(t, `
+	ctx := android.GroupFixturePreparers(
+		prepareForJavaTest,
+		android.FixtureMergeMockFs(
+			map[string][]byte{
+				"a/Android.bp": []byte(provider_bp_a),
+				"b/Android.bp": []byte(provider_bp_b),
+				"c/Android.bp": []byte(provider_bp_c),
+				"d/Android.bp": []byte(provider_bp_d),
+			},
+		),
+		android.FixtureMergeEnv(
+			map[string]string{
+				"DISABLE_STUB_VALIDATION": "true",
+			},
+		),
+	).RunTestWithBp(t, `
 		java_defaults {
 			name: "baz1",
 			api_surface: "public",
@@ -1975,13 +2007,7 @@
 			defaults:["baz1", "baz2"],
 			api_contributions: ["foo4"],
 		}
-		`,
-		map[string][]byte{
-			"a/Android.bp": []byte(provider_bp_a),
-			"b/Android.bp": []byte(provider_bp_b),
-			"c/Android.bp": []byte(provider_bp_c),
-			"d/Android.bp": []byte(provider_bp_d),
-		})
+	`)
 
 	testcases := []struct {
 		moduleName         string
@@ -2026,7 +2052,20 @@
 		api_surface: "public",
 	}
 	`
-	ctx, _ := testJavaWithFS(t, `
+	ctx := android.GroupFixturePreparers(
+		prepareForJavaTest,
+		android.FixtureMergeMockFs(
+			map[string][]byte{
+				"a/Android.bp": []byte(provider_bp_a),
+				"b/Android.bp": []byte(provider_bp_b),
+			},
+		),
+		android.FixtureMergeEnv(
+			map[string]string{
+				"DISABLE_STUB_VALIDATION": "true",
+			},
+		),
+	).RunTestWithBp(t, `
 		java_api_library {
 			name: "bar1",
 			api_surface: "public",
@@ -2038,11 +2077,7 @@
 			api_surface: "system",
 			api_contributions: ["foo1", "foo2"],
 		}
-		`,
-		map[string][]byte{
-			"a/Android.bp": []byte(provider_bp_a),
-			"b/Android.bp": []byte(provider_bp_b),
-		})
+	`)
 
 	testcases := []struct {
 		moduleName    string
@@ -2094,7 +2129,24 @@
 	}
 	`
 
-	ctx, _ := testJavaWithFS(t, `
+	ctx := android.GroupFixturePreparers(
+		prepareForJavaTest,
+		android.FixtureMergeMockFs(
+			map[string][]byte{
+				"a/Android.bp": []byte(provider_bp_a),
+				"b/Android.bp": []byte(provider_bp_b),
+				"c/Android.bp": []byte(lib_bp_a),
+				"c/Lib.java":   {},
+				"d/Android.bp": []byte(lib_bp_b),
+				"d/Lib.java":   {},
+			},
+		),
+		android.FixtureMergeEnv(
+			map[string]string{
+				"DISABLE_STUB_VALIDATION": "true",
+			},
+		),
+	).RunTestWithBp(t, `
 		java_api_library {
 			name: "bar1",
 			api_surface: "public",
@@ -2108,15 +2160,7 @@
 			api_contributions: ["foo1", "foo2"],
 			libs: ["lib1", "lib2", "bar1"],
 		}
-		`,
-		map[string][]byte{
-			"a/Android.bp": []byte(provider_bp_a),
-			"b/Android.bp": []byte(provider_bp_b),
-			"c/Android.bp": []byte(lib_bp_a),
-			"c/Lib.java":   {},
-			"d/Android.bp": []byte(lib_bp_b),
-			"d/Lib.java":   {},
-		})
+	`)
 
 	testcases := []struct {
 		moduleName        string
@@ -2171,7 +2215,24 @@
 	}
 	`
 
-	ctx, _ := testJavaWithFS(t, `
+	ctx := android.GroupFixturePreparers(
+		prepareForJavaTest,
+		android.FixtureMergeMockFs(
+			map[string][]byte{
+				"a/Android.bp": []byte(provider_bp_a),
+				"b/Android.bp": []byte(provider_bp_b),
+				"c/Android.bp": []byte(lib_bp_a),
+				"c/Lib.java":   {},
+				"d/Android.bp": []byte(lib_bp_b),
+				"d/Lib.java":   {},
+			},
+		),
+		android.FixtureMergeEnv(
+			map[string]string{
+				"DISABLE_STUB_VALIDATION": "true",
+			},
+		),
+	).RunTestWithBp(t, `
 		java_api_library {
 			name: "bar1",
 			api_surface: "public",
@@ -2185,15 +2246,7 @@
 			api_contributions: ["foo1", "foo2"],
 			static_libs: ["lib1", "lib2", "bar1"],
 		}
-		`,
-		map[string][]byte{
-			"a/Android.bp": []byte(provider_bp_a),
-			"b/Android.bp": []byte(provider_bp_b),
-			"c/Android.bp": []byte(lib_bp_a),
-			"c/Lib.java":   {},
-			"d/Android.bp": []byte(lib_bp_b),
-			"d/Lib.java":   {},
-		})
+	`)
 
 	testcases := []struct {
 		moduleName        string
@@ -2242,19 +2295,28 @@
 	}
 	`
 
-	ctx, _ := testJavaWithFS(t, `
+	ctx := android.GroupFixturePreparers(
+		prepareForJavaTest,
+		android.FixtureMergeMockFs(
+			map[string][]byte{
+				"a/Android.bp": []byte(provider_bp_a),
+				"b/Android.bp": []byte(provider_bp_b),
+				"c/Android.bp": []byte(lib_bp_a),
+			},
+		),
+		android.FixtureMergeEnv(
+			map[string]string{
+				"DISABLE_STUB_VALIDATION": "true",
+			},
+		),
+	).RunTestWithBp(t, `
 		java_api_library {
 			name: "bar1",
 			api_surface: "public",
 			api_contributions: ["foo1"],
 			full_api_surface_stub: "lib1",
 		}
-		`,
-		map[string][]byte{
-			"a/Android.bp": []byte(provider_bp_a),
-			"b/Android.bp": []byte(provider_bp_b),
-			"c/Android.bp": []byte(lib_bp_a),
-		})
+	`)
 
 	m := ctx.ModuleForTests("bar1", "android_common")
 	manifest := m.Output("metalava.sbox.textproto")
@@ -2402,7 +2464,14 @@
 }
 
 func TestJavaApiContributionImport(t *testing.T) {
-	ctx, _ := testJava(t, `
+	ctx := android.GroupFixturePreparers(
+		prepareForJavaTest,
+		android.FixtureMergeEnv(
+			map[string]string{
+				"DISABLE_STUB_VALIDATION": "true",
+			},
+		),
+	).RunTestWithBp(t, `
 		java_api_library {
 			name: "foo",
 			api_contributions: ["bar"],
@@ -2483,3 +2552,50 @@
 	classPathFlag := "--classpath __SBOX_SANDBOX_DIR__/out/.intermediates/bar/android_common/turbine-combined/bar.jar"
 	android.AssertStringDoesContain(t, "command expected to contain classpath flag", manifestCommand, classPathFlag)
 }
+
+func TestApiLibraryDroidstubsDependency(t *testing.T) {
+	result := android.GroupFixturePreparers(
+		prepareForJavaTest,
+		PrepareForTestWithJavaSdkLibraryFiles,
+		FixtureWithLastReleaseApis("foo"),
+		android.FixtureModifyConfig(func(config android.Config) {
+			config.SetApiLibraries([]string{"foo"})
+		}),
+		android.FixtureMergeMockFs(
+			map[string][]byte{
+				"A.java": nil,
+			},
+		),
+	).RunTestWithBp(t, `
+		java_api_library {
+			name: "foo",
+			api_contributions: [
+				"api-stubs-docs-non-updatable.api.contribution",
+			],
+			enable_validation: true,
+		}
+		java_api_library {
+			name: "bar",
+			api_contributions: [
+				"api-stubs-docs-non-updatable.api.contribution",
+			],
+			enable_validation: false,
+		}
+	`)
+
+	currentApiTimestampPath := "api-stubs-docs-non-updatable/android_common/metalava/check_current_api.timestamp"
+	foo := result.ModuleForTests("foo", "android_common").Module().(*ApiLibrary)
+	fooValidationPathsString := strings.Join(foo.validationPaths.Strings(), " ")
+	bar := result.ModuleForTests("bar", "android_common").Module().(*ApiLibrary)
+	barValidationPathsString := strings.Join(bar.validationPaths.Strings(), " ")
+	android.AssertStringDoesContain(t,
+		"Module expected to have validation",
+		fooValidationPathsString,
+		currentApiTimestampPath,
+	)
+	android.AssertStringDoesNotContain(t,
+		"Module expected to not have validation",
+		barValidationPathsString,
+		currentApiTimestampPath,
+	)
+}
diff --git a/java/sdk_library.go b/java/sdk_library.go
index 78e3102..041aeb7 100644
--- a/java/sdk_library.go
+++ b/java/sdk_library.go
@@ -1838,6 +1838,7 @@
 		Static_libs           []string
 		Full_api_surface_stub *string
 		System_modules        *string
+		Enable_validation     *bool
 	}{}
 
 	props.Name = proptools.StringPtr(module.apiLibraryModuleName(apiScope))
@@ -1885,6 +1886,7 @@
 	}
 
 	props.System_modules = module.deviceProperties.System_modules
+	props.Enable_validation = proptools.BoolPtr(true)
 
 	mctx.CreateModule(ApiLibraryFactory, &props)
 }