license metadata text notice files

Introduce the below command-line tool:

textnotice outputs a NOTICE text file constructed from the license
texts of the transitive closure of dependencies.

Bug: 68860345
Bug: 151177513
Bug: 151953481
Bug: 213388645
Bug: 210912771

Test: m all
Test: m systemlicense
Test: m textnotice; out/soong/host/linux-x85/textnotice ...

where ... is the path to the .meta_lic file for the system image. In my
case if

$ export PRODUCT=$(realpath $ANDROID_PRODUCT_OUT --relative-to=$PWD)

... can be expressed as:

${PRODUCT}/gen/META/lic_intermediates/${PRODUCT}/system.img.meta_lic

Change-Id: Ia691869fd8e58ef008024f48c23b1a4b4435677a
diff --git a/tools/compliance/cmd/textnotice.go b/tools/compliance/cmd/textnotice.go
new file mode 100644
index 0000000..91c57b0
--- /dev/null
+++ b/tools/compliance/cmd/textnotice.go
@@ -0,0 +1,153 @@
+// Copyright 2021 Google LLC
+//
+// 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 (
+	"bytes"
+	"compliance"
+	"flag"
+	"fmt"
+	"io"
+	"io/fs"
+	"os"
+	"path/filepath"
+	"strings"
+)
+
+var (
+	outputFile  = flag.String("o", "-", "Where to write the NOTICE text file. (default stdout)")
+	stripPrefix = flag.String("strip_prefix", "", "Prefix to remove from paths. i.e. path to root")
+
+	failNoneRequested = fmt.Errorf("\nNo license metadata files requested")
+	failNoLicenses    = fmt.Errorf("No licenses found")
+)
+
+type context struct {
+	stdout      io.Writer
+	stderr      io.Writer
+	rootFS      fs.FS
+	stripPrefix string
+}
+
+func init() {
+	flag.Usage = func() {
+		fmt.Fprintf(os.Stderr, `Usage: %s {options} file.meta_lic {file.meta_lic...}
+
+Outputs a text NOTICE file.
+
+Options:
+`, filepath.Base(os.Args[0]))
+		flag.PrintDefaults()
+	}
+}
+
+func main() {
+	flag.Parse()
+
+	// Must specify at least one root target.
+	if flag.NArg() == 0 {
+		flag.Usage()
+		os.Exit(2)
+	}
+
+	if len(*outputFile) == 0 {
+		flag.Usage()
+		fmt.Fprintf(os.Stderr, "must specify file for -o; use - for stdout\n")
+		os.Exit(2)
+	} else {
+		dir, err := filepath.Abs(filepath.Dir(*outputFile))
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "cannot determine path to %q: %w\n", *outputFile, err)
+			os.Exit(1)
+		}
+		fi, err := os.Stat(dir)
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "cannot read directory %q of %q: %w\n", dir, *outputFile, err)
+			os.Exit(1)
+		}
+		if !fi.IsDir() {
+			fmt.Fprintf(os.Stderr, "parent %q of %q is not a directory\n", dir, *outputFile)
+			os.Exit(1)
+		}
+	}
+
+	var ofile io.Writer
+	ofile = os.Stdout
+	if *outputFile != "-" {
+		ofile = &bytes.Buffer{}
+	}
+
+	ctx := &context{ofile, os.Stderr, os.DirFS("."), *stripPrefix}
+
+	err := textNotice(ctx, flag.Args()...)
+	if err != nil {
+		if err == failNoneRequested {
+			flag.Usage()
+		}
+		fmt.Fprintf(os.Stderr, "%s\n", err.Error())
+		os.Exit(1)
+	}
+	if *outputFile != "-" {
+		err := os.WriteFile(*outputFile, ofile.(*bytes.Buffer).Bytes(), 0666)
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "could not write output to %q: %w\n", *outputFile, err)
+			os.Exit(1)
+		}
+	}
+	os.Exit(0)
+}
+
+// textNotice implements the textNotice utility.
+func textNotice(ctx *context, files ...string) error {
+	// Must be at least one root file.
+	if len(files) < 1 {
+		return failNoneRequested
+	}
+
+	// Read the license graph from the license metadata files (*.meta_lic).
+	licenseGraph, err := compliance.ReadLicenseGraph(ctx.rootFS, ctx.stderr, files)
+	if err != nil {
+		return fmt.Errorf("Unable to read license metadata file(s) %q: %v\n", files, err)
+	}
+	if licenseGraph == nil {
+		return failNoLicenses
+	}
+
+	// rs contains all notice resolutions.
+	rs := compliance.ResolveNotices(licenseGraph)
+
+	ni, err := compliance.IndexLicenseTexts(ctx.rootFS, licenseGraph, rs)
+	if err != nil {
+		return fmt.Errorf("Unable to read license text file(s) for %q: %v\n", files, err)
+	}
+
+	for h := range ni.Hashes() {
+		fmt.Fprintln(ctx.stdout, "==============================================================================")
+		for _, libName := range ni.HashLibs(h) {
+			fmt.Fprintf(ctx.stdout, "%s used by:\n", libName)
+			for _, installPath := range ni.HashLibInstalls(h, libName) {
+				if 0 < len(ctx.stripPrefix) && strings.HasPrefix(installPath, ctx.stripPrefix) {
+					fmt.Fprintf(ctx.stdout, "  %s\n", installPath[len(ctx.stripPrefix):])
+				} else {
+					fmt.Fprintf(ctx.stdout, "  %s\n", installPath)
+				}
+			}
+			fmt.Fprintln(ctx.stdout)
+		}
+		ctx.stdout.Write(ni.HashText(h))
+		fmt.Fprintln(ctx.stdout)
+	}
+	return nil
+}