From a87506f5e8a88c0dc925d90970021d47e7e2a359 Mon Sep 17 00:00:00 2001
From: Jeongik Cha <jeongik@google.com>
Date: Thu, 1 Jun 2023 23:16:41 +0900
Subject: [PATCH] Use HINT_FROM_SOONG if ninja_log doesn't exist

In non-incremental build, there is no ninja_log. For this case, use
HINT_FROM_SOONG as an alternative solution.

Bug: 273947040
Test: 1.m after removing out/.ninja_log
      2.check if non-incremental CI build uses HINT_FROM_SOOONG
      3.check if incremental CI build uses NINJA_LOG
      4.check if there is no regression in CUJ
Change-Id: I00cd216df096cb2288eeab233729acefb0d1b73c
---
 cmd/soong_build/main.go | 17 +++++++++++++++--
 ui/build/config.go      | 21 +++++++++++++++++++--
 2 files changed, 34 insertions(+), 4 deletions(-)

diff --git a/cmd/soong_build/main.go b/cmd/soong_build/main.go
index d589925c9..2e6b6d44a 100644
--- a/cmd/soong_build/main.go
+++ b/cmd/soong_build/main.go
@@ -16,6 +16,7 @@ package main
 
 import (
 	"bytes"
+	"errors"
 	"flag"
 	"fmt"
 	"os"
@@ -135,12 +136,24 @@ func runMixedModeBuild(ctx *android.Context, extraNinjaDeps []string) string {
 
 	writeDepFile(cmdlineArgs.OutFile, ctx.EventHandler, ninjaDeps)
 
-	if ctx.Config().IsEnvTrue("SOONG_GENERATES_NINJA_HINT") {
+	if needToWriteNinjaHint(ctx) {
 		writeNinjaHint(ctx)
 	}
 	return cmdlineArgs.OutFile
 }
 
+func needToWriteNinjaHint(ctx *android.Context) bool {
+	switch ctx.Config().GetenvWithDefault("SOONG_GENERATES_NINJA_HINT", "") {
+	case "always":
+		return true
+	case "depend":
+		if _, err := os.Stat(filepath.Join(ctx.Config().OutDir(), ".ninja_log")); errors.Is(err, os.ErrNotExist) {
+			return true
+		}
+	}
+	return false
+}
+
 // Run the code-generation phase to convert BazelTargetModules to BUILD files.
 func runQueryView(queryviewDir, queryviewMarker string, ctx *android.Context) {
 	ctx.EventHandler.Begin("queryview")
@@ -460,7 +473,7 @@ func runSoongOnlyBuild(ctx *android.Context, extraNinjaDeps []string) string {
 		// The actual output (build.ninja) was written in the RunBlueprint() call
 		// above
 		writeDepFile(cmdlineArgs.OutFile, ctx.EventHandler, ninjaDeps)
-		if ctx.Config().IsEnvTrue("SOONG_GENERATES_NINJA_HINT") {
+		if needToWriteNinjaHint(ctx) {
 			writeNinjaHint(ctx)
 		}
 		return cmdlineArgs.OutFile
diff --git a/ui/build/config.go b/ui/build/config.go
index 711774a8a..697cc6611 100644
--- a/ui/build/config.go
+++ b/ui/build/config.go
@@ -16,6 +16,7 @@ package build
 
 import (
 	"encoding/json"
+	"errors"
 	"fmt"
 	"io/ioutil"
 	"math/rand"
@@ -136,6 +137,9 @@ const (
 	EXTERNAL_FILE
 	// ninja uses a prioritized module list from Soong
 	HINT_FROM_SOONG
+	// If ninja log exists, use NINJA_LOG, if not, use HINT_FROM_SOONG instead.
+	// We can assume it is an incremental build if ninja log exists.
+	DEFAULT
 )
 const srcDirFileCheck = "build/soong/root.bp"
 
@@ -233,7 +237,7 @@ func NewConfig(ctx Context, args ...string) Config {
 	ret := &configImpl{
 		environ:               OsEnvironment(),
 		sandboxConfig:         &SandboxConfig{},
-		ninjaWeightListSource: NINJA_LOG,
+		ninjaWeightListSource: DEFAULT,
 	}
 
 	// Default matching ninja
@@ -244,8 +248,21 @@ func NewConfig(ctx Context, args ...string) Config {
 	ret.parseArgs(ctx, args)
 
 	if ret.ninjaWeightListSource == HINT_FROM_SOONG {
-		ret.environ.Set("SOONG_GENERATES_NINJA_HINT", "true")
+		ret.environ.Set("SOONG_GENERATES_NINJA_HINT", "always")
+	} else if ret.ninjaWeightListSource == DEFAULT {
+		defaultNinjaWeightListSource := NINJA_LOG
+		if _, err := os.Stat(filepath.Join(ret.OutDir(), ninjaLogFileName)); errors.Is(err, os.ErrNotExist) {
+			ctx.Verboseln("$OUT/.ninja_log doesn't exist, use HINT_FROM_SOONG instead")
+			defaultNinjaWeightListSource = HINT_FROM_SOONG
+		} else {
+			ctx.Verboseln("$OUT/.ninja_log exist, use NINJA_LOG")
+		}
+		ret.ninjaWeightListSource = defaultNinjaWeightListSource
+		// soong_build generates ninja hint depending on ninja log existence.
+		// Set it "depend" to avoid soong re-run due to env variable change.
+		ret.environ.Set("SOONG_GENERATES_NINJA_HINT", "depend")
 	}
+
 	// Make sure OUT_DIR is set appropriately
 	if outDir, ok := ret.environ.Get("OUT_DIR"); ok {
 		ret.environ.Set("OUT_DIR", filepath.Clean(outDir))