Revert "Revert "Test for dangling rules in make checkbuild""

This reverts commit fb941913a351eca744e8da8251b191a05bccc3a1.

Reapplies I4933187e8b72f2ef0c32d18ffea756e2c6fa417c with fixes
to disable the check for mac builds, where many modules are
disabled and the check is just going to cause more problems.

Test: m checkbuild
Change-Id: If6712c90ececd5d015fcdcdeefe0c3d4f5590711

4 files changed, 108 insertions, 8 deletions

diff --git a/ui/build/Android.bp b/ui/build/Android.bp
index d1b49438..58098943 100644
--- a/ui/build/Android.bp
+++ b/ui/build/Android.bp
@@ -36,6 +36,7 @@ bootstrap_go_package {
         "proc_sync.go",
         "signal.go",
         "soong.go",
+        "test_build.go",
         "util.go",
     ],
     testSrcs: [
diff --git a/ui/build/build.go b/ui/build/build.go
index 0df22b34..78eb6a32 100644
--- a/ui/build/build.go
+++ b/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)
 	}
diff --git a/ui/build/config.go b/ui/build/config.go
index 6e5559d0..df97d803 100644
--- a/ui/build/config.go
+++ b/ui/build/config.go
@@ -34,11 +34,12 @@ type configImpl struct {
 	environ   *Environment
 
 	// From the arguments
-	parallel  int
-	keepGoing int
-	verbose   bool
-	dist      bool
-	skipMake  bool
+	parallel   int
+	keepGoing  int
+	verbose    bool
+	checkbuild bool
+	dist       bool
+	skipMake   bool
 
 	// From the product config
 	katiArgs     []string
@@ -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
 }
diff --git a/ui/build/test_build.go b/ui/build/test_build.go
new file mode 100644
index 00000000..940f0c89
--- /dev/null
+++ b/ui/build/test_build.go
@@ -0,0 +1,85 @@
+// 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"
+	"runtime"
+	"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) {
+	// Many modules are disabled on mac.  Checking for dangling rules would cause lots of build
+	// breakages, and presubmit wouldn't catch them, so just disable the check.
+	if runtime.GOOS != "linux" {
+		return
+	}
+
+	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("")
+	}
+}