Check that API is up-to-date when building java_sdk_library

Previously, the checked in version of an API was only checked to make
sure it was up-to-date when running the checkapi target. This change
adds a validation dependency to the ninja rule that generates the API
from source so that up-to-date check is always performed every time
the API is generated. However, because it is a validation dependency
it does not lengthen the build's critical path.

Bug: 234113632
Test: echo > packages/modules/SdkExtensions/java/android/os/ext/api/current.txt
      m framework-sdkextension
      # Passes without this change even though the checked in API is
      # not up-to-date.
      # With this change the build fails reporting correctly that the
      # checked in API is not up-to-date.
Change-Id: I8e65cf716d94aecd61bd943f1485468664ad4a22
diff --git a/java/droidstubs.go b/java/droidstubs.go
index 115388b..932fb19 100644
--- a/java/droidstubs.go
+++ b/java/droidstubs.go
@@ -697,87 +697,16 @@
 
 	zipSyncCleanupCmd(rule, srcJarDir)
 
-	rule.Build("metalava", "metalava merged")
-
 	if apiCheckEnabled(ctx, d.properties.Check_api.Current, "current") {
+		d.generateCheckCurrentCheckedInApiIsUpToDateBuildRules(ctx)
 
-		if len(d.Javadoc.properties.Out) > 0 {
-			ctx.PropertyErrorf("out", "out property may not be combined with check_api")
-		}
-
-		apiFile := android.PathForModuleSrc(ctx, String(d.properties.Check_api.Current.Api_file))
-		removedApiFile := android.PathForModuleSrc(ctx, String(d.properties.Check_api.Current.Removed_api_file))
-		baselineFile := android.OptionalPathForModuleSrc(ctx, d.properties.Check_api.Current.Baseline_file)
-
-		if baselineFile.Valid() {
-			ctx.PropertyErrorf("baseline_file", "current API check can't have a baseline file. (module %s)", ctx.ModuleName())
-		}
-
-		d.checkCurrentApiTimestamp = android.PathForModuleOut(ctx, "metalava", "check_current_api.timestamp")
-
-		rule := android.NewRuleBuilder(pctx, ctx)
-
-		// Diff command line.
-		// -F matches the closest "opening" line, such as "package android {"
-		// and "  public class Intent {".
-		diff := `diff -u -F '{ *$'`
-
-		rule.Command().Text("( true")
-		rule.Command().
-			Text(diff).
-			Input(apiFile).Input(d.apiFile)
-
-		rule.Command().
-			Text(diff).
-			Input(removedApiFile).Input(d.removedApiFile)
-
-		msg := fmt.Sprintf(`\n******************************\n`+
-			`You have tried to change the API from what has been previously approved.\n\n`+
-			`To make these errors go away, you have two choices:\n`+
-			`   1. You can add '@hide' javadoc comments (and remove @SystemApi/@TestApi/etc)\n`+
-			`      to the new methods, etc. shown in the above diff.\n\n`+
-			`   2. You can update current.txt and/or removed.txt by executing the following command:\n`+
-			`         m %s-update-current-api\n\n`+
-			`      To submit the revised current.txt to the main Android repository,\n`+
-			`      you will need approval.\n`+
-			`******************************\n`, ctx.ModuleName())
-
-		rule.Command().
-			Text("touch").Output(d.checkCurrentApiTimestamp).
-			Text(") || (").
-			Text("echo").Flag("-e").Flag(`"` + msg + `"`).
-			Text("; exit 38").
-			Text(")")
-
-		rule.Build("metalavaCurrentApiCheck", "check current API")
-
-		d.updateCurrentApiTimestamp = android.PathForModuleOut(ctx, "metalava", "update_current_api.timestamp")
-
-		// update API rule
-		rule = android.NewRuleBuilder(pctx, ctx)
-
-		rule.Command().Text("( true")
-
-		rule.Command().
-			Text("cp").Flag("-f").
-			Input(d.apiFile).Flag(apiFile.String())
-
-		rule.Command().
-			Text("cp").Flag("-f").
-			Input(d.removedApiFile).Flag(removedApiFile.String())
-
-		msg = "failed to update public API"
-
-		rule.Command().
-			Text("touch").Output(d.updateCurrentApiTimestamp).
-			Text(") || (").
-			Text("echo").Flag("-e").Flag(`"` + msg + `"`).
-			Text("; exit 38").
-			Text(")")
-
-		rule.Build("metalavaCurrentApiUpdate", "update current API")
+		// Make sure that whenever the API stubs are generated that the current checked in API files are
+		// checked to make sure that they are up-to-date.
+		cmd.Validation(d.checkCurrentApiTimestamp)
 	}
 
+	rule.Build("metalava", "metalava merged")
+
 	if String(d.properties.Check_nullability_warnings) != "" {
 		if d.nullabilityWarningsFile == nil {
 			ctx.PropertyErrorf("check_nullability_warnings",
@@ -814,6 +743,84 @@
 	}
 }
 
+func (d *Droidstubs) generateCheckCurrentCheckedInApiIsUpToDateBuildRules(ctx android.ModuleContext) {
+	if len(d.Javadoc.properties.Out) > 0 {
+		ctx.PropertyErrorf("out", "out property may not be combined with check_api")
+	}
+
+	apiFile := android.PathForModuleSrc(ctx, String(d.properties.Check_api.Current.Api_file))
+	removedApiFile := android.PathForModuleSrc(ctx, String(d.properties.Check_api.Current.Removed_api_file))
+	baselineFile := android.OptionalPathForModuleSrc(ctx, d.properties.Check_api.Current.Baseline_file)
+
+	if baselineFile.Valid() {
+		ctx.PropertyErrorf("baseline_file", "current API check can't have a baseline file. (module %s)", ctx.ModuleName())
+	}
+
+	d.checkCurrentApiTimestamp = android.PathForModuleOut(ctx, "metalava", "check_current_api.timestamp")
+
+	rule := android.NewRuleBuilder(pctx, ctx)
+
+	// Diff command line.
+	// -F matches the closest "opening" line, such as "package android {"
+	// and "  public class Intent {".
+	diff := `diff -u -F '{ *$'`
+
+	rule.Command().Text("( true")
+	rule.Command().
+		Text(diff).
+		Input(apiFile).Input(d.apiFile)
+
+	rule.Command().
+		Text(diff).
+		Input(removedApiFile).Input(d.removedApiFile)
+
+	msg := fmt.Sprintf(`\n******************************\n`+
+		`You have tried to change the API from what has been previously approved.\n\n`+
+		`To make these errors go away, you have two choices:\n`+
+		`   1. You can add '@hide' javadoc comments (and remove @SystemApi/@TestApi/etc)\n`+
+		`      to the new methods, etc. shown in the above diff.\n\n`+
+		`   2. You can update current.txt and/or removed.txt by executing the following command:\n`+
+		`         m %s-update-current-api\n\n`+
+		`      To submit the revised current.txt to the main Android repository,\n`+
+		`      you will need approval.\n`+
+		`******************************\n`, ctx.ModuleName())
+
+	rule.Command().
+		Text("touch").Output(d.checkCurrentApiTimestamp).
+		Text(") || (").
+		Text("echo").Flag("-e").Flag(`"` + msg + `"`).
+		Text("; exit 38").
+		Text(")")
+
+	rule.Build("metalavaCurrentApiCheck", "check current API")
+
+	d.updateCurrentApiTimestamp = android.PathForModuleOut(ctx, "metalava", "update_current_api.timestamp")
+
+	// update API rule
+	rule = android.NewRuleBuilder(pctx, ctx)
+
+	rule.Command().Text("( true")
+
+	rule.Command().
+		Text("cp").Flag("-f").
+		Input(d.apiFile).Flag(apiFile.String())
+
+	rule.Command().
+		Text("cp").Flag("-f").
+		Input(d.removedApiFile).Flag(removedApiFile.String())
+
+	msg = "failed to update public API"
+
+	rule.Command().
+		Text("touch").Output(d.updateCurrentApiTimestamp).
+		Text(") || (").
+		Text("echo").Flag("-e").Flag(`"` + msg + `"`).
+		Text("; exit 38").
+		Text(")")
+
+	rule.Build("metalavaCurrentApiUpdate", "update current API")
+}
+
 func StubsDefaultsFactory() android.Module {
 	module := &DocDefaults{}