Revert "Revert "Revert "Revert "Add path interposer""""

This reverts commit 09f4540d66.

Fixes the raw call to net.Listen in the tests to go through the listen()
helper and use the long socket path fallbacks.

Removes the use of timeouts from the tests -- the behaviors being tested
did not rely on timeouts, so removing them will reduce the flakiness if
the build is heavily loading the machine at the same time the test is
running.

Also fixes some potential nil pointer dereferences.

Test: OUT_DIR=<really long> m blueprint_tools
Test: `while .../soong-ui-build-paths/test/test; do sleep 0.01; done` with a build running
Change-Id: I16d44be7517bc415f1c808284088f4ba40df3bfa

cmd/path_interposer/main_test.go

@@ -0,0 +1,196 @@
+// Copyright 2018 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 main
+
+import (
+	"fmt"
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"testing"
+
+	"android/soong/ui/build/paths"
+)
+
+var tmpDir string
+var origPATH string
+
+func TestMain(m *testing.M) {
+	os.Exit(func() int {
+		var err error
+		tmpDir, err = ioutil.TempDir("", "interposer_test")
+		if err != nil {
+			panic(err)
+		}
+		defer os.RemoveAll(tmpDir)
+
+		origPATH = os.Getenv("PATH")
+		err = os.Setenv("PATH", "")
+		if err != nil {
+			panic(err)
+		}
+
+		return m.Run()
+	}())
+}
+
+func setup(t *testing.T) string {
+	f, err := ioutil.TempFile(tmpDir, "interposer")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer f.Close()
+
+	err = ioutil.WriteFile(f.Name()+"_origpath", []byte(origPATH), 0666)
+	if err != nil {
+		t.Fatal(err)
+	}
+	return f.Name()
+}
+
+func TestInterposer(t *testing.T) {
+	interposer := setup(t)
+
+	logConfig := func(name string) paths.PathConfig {
+		if name == "true" {
+			return paths.PathConfig{
+				Log:   false,
+				Error: false,
+			}
+		} else if name == "path_interposer_test_not_allowed" {
+			return paths.PathConfig{
+				Log:   false,
+				Error: true,
+			}
+		}
+		return paths.PathConfig{
+			Log:   true,
+			Error: false,
+		}
+	}
+
+	testCases := []struct {
+		name string
+		args []string
+
+		exitCode int
+		err      error
+		logEntry string
+	}{
+		{
+			name: "direct call",
+			args: []string{interposer},
+
+			exitCode: 1,
+			err:      usage,
+		},
+		{
+			name: "relative call",
+			args: []string{filepath.Base(interposer)},
+
+			exitCode: 1,
+			err:      usage,
+		},
+		{
+			name: "true",
+			args: []string{"/my/path/true"},
+		},
+		{
+			name: "relative true",
+			args: []string{"true"},
+		},
+		{
+			name: "exit code",
+			args: []string{"bash", "-c", "exit 42"},
+
+			exitCode: 42,
+			logEntry: "bash",
+		},
+		{
+			name: "signal",
+			args: []string{"bash", "-c", "kill -9 $$"},
+
+			exitCode: 137,
+			logEntry: "bash",
+		},
+		{
+			name: "does not exist",
+			args: []string{"path_interposer_test_does_not_exist"},
+
+			exitCode: 1,
+			err:      fmt.Errorf(`exec: "path_interposer_test_does_not_exist": executable file not found in $PATH`),
+			logEntry: "path_interposer_test_does_not_exist",
+		},
+		{
+			name: "not allowed",
+			args: []string{"path_interposer_test_not_allowed"},
+
+			exitCode: 1,
+			err:      fmt.Errorf(`"path_interposer_test_not_allowed" is not allowed to be used. See https://android.googlesource.com/platform/build/+/master/Changes.md#PATH_Tools for more information.`),
+			logEntry: "path_interposer_test_not_allowed",
+		},
+	}
+
+	for _, testCase := range testCases {
+		t.Run(testCase.name, func(t *testing.T) {
+			logged := false
+			logFunc := func(logSocket string, entry *paths.LogEntry, done chan interface{}) {
+				defer close(done)
+
+				logged = true
+				if entry.Basename != testCase.logEntry {
+					t.Errorf("unexpected log entry:\nwant: %q\n got: %q", testCase.logEntry, entry.Basename)
+				}
+			}
+
+			exitCode, err := Main(ioutil.Discard, ioutil.Discard, interposer, testCase.args, mainOpts{
+				sendLog: logFunc,
+				config:  logConfig,
+			})
+
+			errstr := func(err error) string {
+				if err == nil {
+					return ""
+				}
+				return err.Error()
+			}
+			if errstr(testCase.err) != errstr(err) {
+				t.Errorf("unexpected error:\nwant: %v\n got: %v", testCase.err, err)
+			}
+			if testCase.exitCode != exitCode {
+				t.Errorf("expected exit code %d, got %d", testCase.exitCode, exitCode)
+			}
+			if !logged && testCase.logEntry != "" {
+				t.Errorf("no log entry, but expected %q", testCase.logEntry)
+			}
+		})
+	}
+}
+
+func TestMissingPath(t *testing.T) {
+	interposer := setup(t)
+	err := os.Remove(interposer + "_origpath")
+	if err != nil {
+		t.Fatalf("Failed to remove:", err)
+	}
+
+	exitCode, err := Main(ioutil.Discard, ioutil.Discard, interposer, []string{"true"}, mainOpts{})
+	if err != usage {
+		t.Errorf("Unexpected error:\n got: %v\nwant: %v", err, usage)
+	}
+	if exitCode != 1 {
+		t.Errorf("expected exit code %d, got %d", 1, exitCode)
+	}
+}