compliance package for license metadata: dumpgraph

package to read, consume, and analyze license metadata and dependency
graph.

Includes testdata/ and the the below command-line tool:

dumpgraph outputs edges of the graph as "target dependency annotations"

Bug: 68860345
Bug: 151177513
Bug: 151953481

Test: m all
Test: m systemlicense
Test: m dumpgraph; out/soong/host/linux-x86/dumpgraph ...

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: I5fe57d361da5155dbcb2c0d369626e9200c9d664
diff --git a/tools/compliance/cmd/dumpgraph.go b/tools/compliance/cmd/dumpgraph.go
new file mode 100644
index 0000000..1ee63b2
--- /dev/null
+++ b/tools/compliance/cmd/dumpgraph.go
@@ -0,0 +1,178 @@
+// 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 (
+	"compliance"
+	"flag"
+	"fmt"
+	"io"
+	"os"
+	"path/filepath"
+	"sort"
+	"strings"
+)
+
+var (
+	graphViz        = flag.Bool("dot", false, "Whether to output graphviz (i.e. dot) format.")
+	labelConditions = flag.Bool("label_conditions", false, "Whether to label target nodes with conditions.")
+	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 {
+	graphViz        bool
+	labelConditions bool
+	stripPrefix     string
+}
+
+func init() {
+	flag.Usage = func() {
+		fmt.Fprintf(os.Stderr, `Usage: %s {options} file.meta_lic {file.meta_lic...}
+
+Outputs space-separated Target Dependency Annotations tuples for each
+edge in the license graph. When -dot flag given, outputs the nodes and
+edges in graphViz directed graph format.
+
+In plain text mode, multiple values within a field are colon-separated.
+e.g. multiple annotations appear as annotation1:annotation2:annotation3
+or when -label_conditions is requested, Target and Dependency become
+target:condition1:condition2 etc.
+
+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)
+	}
+
+	ctx := &context{*graphViz, *labelConditions, *stripPrefix}
+
+	err := dumpGraph(ctx, os.Stdout, os.Stderr, flag.Args()...)
+	if err != nil {
+		if err == failNoneRequested {
+			flag.Usage()
+		}
+		fmt.Fprintf(os.Stderr, "%s\n", err.Error())
+		os.Exit(1)
+	}
+	os.Exit(0)
+}
+
+// dumpGraph implements the dumpgraph utility.
+func dumpGraph(ctx *context, stdout, stderr io.Writer, files ...string) error {
+	if len(files) < 1 {
+		return failNoneRequested
+	}
+
+	// Read the license graph from the license metadata files (*.meta_lic).
+	licenseGraph, err := compliance.ReadLicenseGraph(os.DirFS("."), stderr, files)
+	if err != nil {
+		return fmt.Errorf("Unable to read license metadata file(s) %q: %w\n", files, err)
+	}
+	if licenseGraph == nil {
+		return failNoLicenses
+	}
+
+	// Sort the edges of the graph.
+	edges := licenseGraph.Edges()
+	sort.Sort(edges)
+
+	// nodes maps license metadata file names to graphViz node names when ctx.graphViz is true.
+	var nodes map[string]string
+	n := 0
+
+	// targetOut calculates the string to output for `target` separating conditions as needed using `sep`.
+	targetOut := func(target *compliance.TargetNode, sep string) string {
+		tOut := strings.TrimPrefix(target.Name(), ctx.stripPrefix)
+		if ctx.labelConditions {
+			conditions := target.LicenseConditions().Names()
+			sort.Strings(conditions)
+			if len(conditions) > 0 {
+				tOut += sep + strings.Join(conditions, sep)
+			}
+		}
+		return tOut
+	}
+
+	// makeNode maps `target` to a graphViz node name.
+	makeNode := func(target *compliance.TargetNode) {
+		tName := target.Name()
+		if _, ok := nodes[tName]; !ok {
+			nodeName := fmt.Sprintf("n%d", n)
+			nodes[tName] = nodeName
+			fmt.Fprintf(stdout, "\t%s [label=\"%s\"];\n", nodeName, targetOut(target, "\\n"))
+			n++
+		}
+	}
+
+	// If graphviz output, map targets to node names, and start the directed graph.
+	if ctx.graphViz {
+		nodes = make(map[string]string)
+		targets := licenseGraph.Targets()
+		sort.Sort(targets)
+
+		fmt.Fprintf(stdout, "strict digraph {\n\trankdir=RL;\n")
+		for _, target := range targets {
+			makeNode(target)
+		}
+	}
+
+	// Print the sorted edges to stdout ...
+	for _, e := range edges {
+		// sort the annotations for repeatability/stability
+		annotations := e.Annotations().AsList()
+		sort.Strings(annotations)
+
+		tName := e.Target().Name()
+		dName := e.Dependency().Name()
+
+		if ctx.graphViz {
+			// ... one edge per line labelled with \\n-separated annotations.
+			tNode := nodes[tName]
+			dNode := nodes[dName]
+			fmt.Fprintf(stdout, "\t%s -> %s [label=\"%s\"];\n", dNode, tNode, strings.Join(annotations, "\\n"))
+		} else {
+			// ... one edge per line with annotations in a colon-separated tuple.
+			fmt.Fprintf(stdout, "%s %s %s\n", targetOut(e.Target(), ":"), targetOut(e.Dependency(), ":"), strings.Join(annotations, ":"))
+		}
+	}
+
+	// If graphViz output, rank the root nodes together, and complete the directed graph.
+	if ctx.graphViz {
+		fmt.Fprintf(stdout, "\t{rank=same;")
+		for _, f := range files {
+			fName := f
+			if !strings.HasSuffix(fName, ".meta_lic") {
+				fName += ".meta_lic"
+			}
+			if fNode, ok := nodes[fName]; ok {
+				fmt.Fprintf(stdout, " %s", fNode)
+			}
+		}
+		fmt.Fprintf(stdout, "}\n}\n")
+	}
+	return nil
+}