Test for dangling rules in make checkbuild

Get a list of leaf nodes in the dependency graph
from ninja, and make sure none of them are in the
output directory.  This ensures that there are no
rules that depend on a file in the output directory
that doesn't have rule to generate it.  The check
will catch a common set of build failures where
a rule to generate a file is deleted (either by
deleting a module in an Android.mk file, or by
modifying the build system incorrectly).  These
failures are often not caught by a local incremental
build because the previously built files are still
present in the output directory.

Bug: 36843214
Bug: 68062417
Test: manual
Change-Id: I4933187e8b72f2ef0c32d18ffea756e2c6fa417c

cmd/soong_ui/main.go

@@ -114,7 +114,11 @@ func main() {
 	} else if os.Args[1] == "--dumpvars-mode" {
 		dumpVars(buildCtx, config, os.Args[2:])
 	} else {
-		build.Build(buildCtx, config, build.BuildAll)
+		toBuild := build.BuildAll
+		if config.Checkbuild() {
+			toBuild |= build.RunBuildTests
+		}
+		build.Build(buildCtx, config, toBuild)
 	}
 }
 

ui/build/Android.bp

@@ -36,6 +36,7 @@ bootstrap_go_package {
         "proc_sync.go",
         "signal.go",
         "soong.go",
+        "test_build.go",
         "util.go",
     ],
     testSrcs: [

ui/build/build.go

@@ -68,6 +68,7 @@ const (
 	BuildSoong         = 1 << iota
 	BuildKati          = 1 << iota
 	BuildNinja         = 1 << iota
+	RunBuildTests      = 1 << iota
 	BuildAll           = BuildProductConfig | BuildSoong | BuildKati | BuildNinja
 )
 
@@ -172,14 +173,18 @@ func Build(ctx Context, config Config, what int) {
 		}
 	}
 
+	// Write combined ninja file
+	createCombinedBuildNinjaFile(ctx, config)
+
+	if what&RunBuildTests != 0 {
+		testForDanglingRules(ctx, config)
+	}
+
 	if what&BuildNinja != 0 {
 		if !config.SkipMake() {
 			installCleanIfNecessary(ctx, config)
 		}
 
-		// Write combined ninja file
-		createCombinedBuildNinjaFile(ctx, config)
-
 		// Run ninja
 		runNinja(ctx, config)
 	}

ui/build/config.go

@@ -37,6 +37,7 @@ type configImpl struct {
 	parallel   int
 	keepGoing  int
 	verbose    bool
+	checkbuild bool
 	dist       bool
 	skipMake   bool
 
@@ -206,6 +207,8 @@ func (c *configImpl) parseArgs(ctx Context, args []string) {
 		} else {
 			if arg == "dist" {
 				c.dist = true
+			} else if arg == "checkbuild" {
+				c.checkbuild = true
 			}
 			c.arguments = append(c.arguments, arg)
 		}
@@ -313,6 +316,12 @@ func (c *configImpl) KatiSuffix() string {
 	panic("SetKatiSuffix has not been called")
 }
 
+// Checkbuild returns true if "checkbuild" was one of the build goals, which means that the
+// user is interested in additional checks at the expense of build time.
+func (c *configImpl) Checkbuild() bool {
+	return c.checkbuild
+}
+
 func (c *configImpl) Dist() bool {
 	return c.dist
 }

ui/build/test_build.go

@@ -0,0 +1,78 @@
+// Copyright 2017 Google Inc. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package build
+
+import (
+	"bufio"
+	"path/filepath"
+	"strings"
+)
+
+// Checks for files in the out directory that have a rule that depends on them but no rule to
+// create them. This catches a common set of build failures where a rule to generate a file is
+// deleted (either by deleting a module in an Android.mk file, or by modifying the build system
+// incorrectly).  These failures are often not caught by a local incremental build because the
+// previously built files are still present in the output directory.
+func testForDanglingRules(ctx Context, config Config) {
+	ctx.BeginTrace("test for dangling rules")
+	defer ctx.EndTrace()
+
+	// Get a list of leaf nodes in the dependency graph from ninja
+	executable := config.PrebuiltBuildTool("ninja")
+
+	args := []string{}
+	args = append(args, config.NinjaArgs()...)
+	args = append(args, "-f", config.CombinedNinjaFile())
+	args = append(args, "-t", "targets", "rule")
+
+	cmd := Command(ctx, config, "ninja", executable, args...)
+	stdout, err := cmd.StdoutPipe()
+	if err != nil {
+		ctx.Fatal(err)
+	}
+
+	cmd.StartOrFatal()
+
+	outDir := config.OutDir()
+	bootstrapDir := filepath.Join(outDir, "soong", ".bootstrap")
+	miniBootstrapDir := filepath.Join(outDir, "soong", ".minibootstrap")
+
+	var danglingRules []string
+
+	scanner := bufio.NewScanner(stdout)
+	for scanner.Scan() {
+		line := scanner.Text()
+		if !strings.HasPrefix(line, outDir) {
+			// Leaf node is not in the out directory.
+			continue
+		}
+		if strings.HasPrefix(line, bootstrapDir) || strings.HasPrefix(line, miniBootstrapDir) {
+			// Leaf node is in one of Soong's bootstrap directories, which do not have
+			// full build rules in the primary build.ninja file.
+			continue
+		}
+		danglingRules = append(danglingRules, line)
+	}
+
+	cmd.WaitOrFatal()
+
+	if len(danglingRules) > 0 {
+		ctx.Println("Dependencies in out found with no rule to create them:")
+		for _, dep := range danglingRules {
+			ctx.Println(dep)
+		}
+		ctx.Fatal("")
+	}
+}