tools/src/cmd/gen/build/build.go - dawn - Git at Google

 // Copyright 2023 The Tint Authors.
 //
 // 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 implements a extensible build file list and module dependency
 // generator for Tint.
 // See: docs/tint/gen.md
 package build

 import (
 	"bytes"
 	"context"
 	"encoding/json"
 	"flag"
 	"fmt"
 	"log"
 	"os"
 	"os/exec"
 	"path"
 	"path/filepath"
 	"regexp"
 	"strings"

 	"dawn.googlesource.com/dawn/tools/src/cmd/gen/common"
 	"dawn.googlesource.com/dawn/tools/src/container"
 	"dawn.googlesource.com/dawn/tools/src/fileutils"
 	"dawn.googlesource.com/dawn/tools/src/glob"
 	"dawn.googlesource.com/dawn/tools/src/match"
 	"dawn.googlesource.com/dawn/tools/src/template"
 	"dawn.googlesource.com/dawn/tools/src/transform"
 	"github.com/mzohreva/gographviz/graphviz"
 	"github.com/tidwall/jsonc"
 )

 const srcTint = "src/tint"

 func init() {
 	common.Register(&Cmd{})
 }

 type Cmd struct {
 	flags struct {
 		dot bool
 	}
 }

 func (Cmd) Name() string {
 	return "build"
 }

 func (Cmd) Desc() string {
 	return `build generates BUILD.* files in each of Tint's source directories`
 }

 func (c *Cmd) RegisterFlags(ctx context.Context, cfg *common.Config) ([]string, error) {
 	flag.BoolVar(&c.flags.dot, "dot", false, "emit GraphViz DOT files for each target kind")
 	return nil, nil
 }

 func (c Cmd) Run(ctx context.Context, cfg *common.Config) error {
 	p := NewProject(CanonicalizePath(path.Join(fileutils.DawnRoot(), srcTint)), cfg)

 	for _, stage := range []struct {
 		desc string
 		fn   func(p *Project) error
 	}{
 		{"loading 'externals.json'", loadExternals},
 		{"populating source files", populateSourceFiles},
 		{"scanning source files", scanSourceFiles},
 		{"loading directory configs", applyDirectoryConfigs},
 		{"building dependencies", buildDependencies},
 		{"checking for cycles", checkForCycles},
 		{"emitting build files", emitBuildFiles},
 	} {
 		if cfg.Flags.Verbose {
 			log.Printf("%v...\n", stage.desc)
 		}
 		if err := stage.fn(p); err != nil {
 			return err
 		}
 	}

 	if c.flags.dot {
 		for _, kind := range AllTargetKinds {
 			if err := emitDotFile(p, kind); err != nil {
 				return err
 			}
 		}
 	}

 	if cfg.Flags.Verbose {
 		log.Println("done")
 	}
 	return nil
 }

 // loadExternals loads the 'externals.json' file in this directory.
 func loadExternals(p *Project) error {
 	content, err := os.ReadFile(path.Join(fileutils.ThisDir(), "externals.json"))
 	if err != nil {
 		return err
 	}

 	externals := container.NewMap[string, struct {
 		IncludePattern string `json:"include_pattern"`
 		Condition      string
 	}]()
 	if err := json.Unmarshal(jsonc.ToJSON(content), &externals); err != nil {
 		return fmt.Errorf("failed to parse 'externals.json': %w", err)
 	}

 	for _, name := range externals.Keys() {
 		external := externals[name]
 		match, err := match.New(external.IncludePattern)
 		if err != nil {
 			return fmt.Errorf("'externals.json' matcher error: %w", err)
 		}
 		name := ExternalDependencyName(name)
 		p.externals.Add(name, ExternalDependency{
 			Name:                name,
 			Condition:           external.Condition,
 			includePatternMatch: match,
 		})
 	}

 	return nil
 }

 // Globs all the source files, and creates populates the Project with Directory, Target and File.
 // File name patterns are used to bin each file into a target for the directory.
 func populateSourceFiles(p *Project) error {
 	paths, err := glob.Scan(p.Root, glob.MustParseConfig(`{
 		"paths": [
 			{
 				"include": [
 					"*/**.cc",
 					"*/**.h",
 					"*/**.inl"
 				]
 			},
 			{
 				"exclude": [
 					"fuzzers/**"
 				]
 			}]
 	}`))
 	if err != nil {
 		return err
 	}

 	for _, filepath := range paths {
 		filepath = CanonicalizePath(filepath)
 		dir, name := path.Split(filepath)
 		if kind := targetKindFromFilename(name); kind != targetInvalid {
 			directory := p.AddDirectory(dir)
 			p.AddTarget(directory, kind).AddSourceFile(p.AddFile(filepath))
 		}
 	}

 	return nil
 }

 // scanSourceFiles scans all the source files for:
 // * #includes to build a dependencies between targets
 // * 'GEN_BUILD:' directives
 func scanSourceFiles(p *Project) error {
 	// ParsedFile describes all the includes and conditions found in a source file
 	type ParsedFile struct {
 		conditions []string
 		includes   []Include
 	}

 	// parseFile parses the source file at 'path' represented by 'file'
 	// As this is run concurrently, it must not modify any shared state (including file)
 	parseFile := func(path string, file *File) (string, *ParsedFile, error) {
 		body, err := os.ReadFile(file.AbsPath())
 		if err != nil {
 			return path, nil, err
 		}
 		out := &ParsedFile{}
 		for i, line := range strings.Split(string(body), "\n") {
 			if match := reCondition.FindStringSubmatch(line); len(match) > 0 {
 				out.conditions = append(out.conditions, match[1])
 			}
 			if !reIgnoreInclude.MatchString(line) {
 				if match := reInclude.FindStringSubmatch(line); len(match) > 0 {
 					out.includes = append(out.includes, Include{match[1], i + 1})
 				}
 			}
 		}
 		return path, out, nil
 	}

 	// Create a new map by calling parseFile() on each entry of p.Files
 	// This is performed over multiple concurrent goroutines.
 	parsedFiles, err := transform.GoMap(p.Files, parseFile)
 	if err != nil {
 		return err
 	}

 	// For each file, of each target, of each directory...
 	for _, dir := range p.Directories {
 		for _, target := range dir.Targets() {
 			for _, file := range target.SourceFiles() {
 				// Retrieve the parsed file information
 				parsed := parsedFiles[file.Path()]

 				// Apply any conditions
 				for _, condition := range parsed.conditions {
 					if file.Condition == "" {
 						file.Condition = condition
 					} else {
 						file.Condition += " && " + condition
 					}
 				}

 				file.Includes = append(file.Includes, parsed.includes...)
 			}
 		}
 	}
 	return nil
 }

 // applyDirectoryConfigs loads a 'BUILD.cfg' file in each source directory (if found), and
 // applies the config to the Directory and/or Targets.
 func applyDirectoryConfigs(p *Project) error {
 	// Config for a single target of a directory
 	type TargetConfig struct {
 		AdditionalDependencies []string
 	}
 	// Config for a directory
 	type DirectoryConfig struct {
 		// Condition for all targets in the directory
 		Condition string
 		// Configuration for the 'lib' target
 		Lib TargetConfig
 		// Configuration for the 'test' target
 		Test TargetConfig
 		// Configuration for the 'bench' target
 		Bench TargetConfig
 		// Configuration for the 'cmd' target
 		Cmd TargetConfig
 	}

 	// For each directory in the project...
 	for _, dir := range p.Directories.Values() {
 		path := path.Join(dir.AbsPath(), "BUILD.cfg")
 		content, err := os.ReadFile(path)
 		if err != nil {
 			continue
 		}

 		// Parse the config
 		cfg := DirectoryConfig{}
 		if err := json.Unmarshal(jsonc.ToJSON(content), &cfg); err != nil {
 			return fmt.Errorf("error while parsing '%v': %w", path, err)
 		}

 		// Apply any directory-level condition
 		for _, target := range dir.Targets() {
 			target.Condition = cfg.Condition
 		}

 		// For each target config...
 		for _, tc := range []struct {
 			cfg  *TargetConfig
 			kind TargetKind
 		}{
 			{&cfg.Lib, targetLib},
 			{&cfg.Test, targetTest},
 			{&cfg.Bench, targetBench},
 			{&cfg.Cmd, targetCmd},
 		} {
 			// Add any additional dependencies
 			for _, depPattern := range tc.cfg.AdditionalDependencies {
 				match, err := match.New(depPattern)
 				if err != nil {
 					return fmt.Errorf("%v: failed to parse %v.AdditionalDependencies '%v': %w", path, tc.kind, depPattern, err)
 				}
 				additionalDeps := []*Target{}
 				for _, target := range p.Targets.Keys() {
 					if match(string(target)) {
 						additionalDeps = append(additionalDeps, p.Targets[target])
 					}
 				}
 				if len(additionalDeps) == 0 {
 					return fmt.Errorf("%v: %v.AdditionalDependencies '%v' did not match any targets", path, tc.kind, depPattern)
 				}
 				target := p.AddTarget(dir, tc.kind)
 				for _, dep := range additionalDeps {
 					if dep != target {
 						target.Dependencies.AddInternal(dep)
 					}
 				}
 			}
 		}
 	}

 	return nil
 }

 // buildDependencies walks all the #includes in all files, building the dependency information for
 // all targets and files in the project. Errors if any cyclic includes are found.
 func buildDependencies(p *Project) error {
 	type state int
 	const (
 		unvisited state = iota
 		visiting
 		checked
 	)

 	cache := container.NewMap[string, state]()

 	type FileInclude struct {
 		file string
 		inc  Include
 	}

 	var walk func(file *File, route []FileInclude) error
 	walk = func(file *File, route []FileInclude) error {
 		// Adds the dependency to the file and target's list of internal dependencies
 		addInternalDependency := func(dep *Target) {
 			file.TransitiveDependencies.AddInternal(dep)
 			if file.Target != dep {
 				file.Target.Dependencies.AddInternal(dep)
 			}
 		}
 		// Adds the dependency to the file and target's list of external dependencies
 		addExternalDependency := func(dep ExternalDependency) {
 			file.TransitiveDependencies.AddExternal(dep)
 			file.Target.Dependencies.AddExternal(dep)
 		}

 		filePath := file.Path()
 		switch cache[filePath] {
 		case unvisited:
 			cache[filePath] = visiting

 			for _, include := range file.Includes {
 				if strings.HasPrefix(include.Path, srcTint) {
 					// #include "src/tint/..."
 					path := include.Path[len(srcTint)+1:] // Strip 'src/tint/'

 					includeFile := p.File(path)
 					if includeFile == nil {
 						return fmt.Errorf(`%v:%v includes non-existent file '%v'`, file.Path(), include.Line, path)
 					}

 					if file.Target.Kind == targetLib && includeFile.Target.Kind != targetLib {
 						return fmt.Errorf(`%v:%v lib target must not include %v target`, file.Path(), include.Line, includeFile.Target.Kind)
 					}

 					addInternalDependency(includeFile.Target)

 					// Gather the dependencies for the included file
 					if err := walk(includeFile, append(route, FileInclude{file: file.Path(), inc: include})); err != nil {
 						return err
 					}

 					for _, dependency := range includeFile.TransitiveDependencies.Internal() {
 						addInternalDependency(dependency)
 					}
 					for _, dependency := range includeFile.TransitiveDependencies.External() {
 						addExternalDependency(dependency)
 					}

 				} else {
 					// Check for external includes
 					for _, external := range p.externals.Values() {
 						if external.includePatternMatch(include.Path) {
 							addExternalDependency(external)
 						}
 					}
 				}

 			}

 			cache[filePath] = checked

 		case visiting:
 			err := strings.Builder{}
 			fmt.Fprintln(&err, "cyclic include found:")
 			for _, include := range route {
 				fmt.Fprintf(&err, "  %v:%v includes '%v'\n", include.file, include.inc.Line, include.inc.Path)
 			}
 			return fmt.Errorf(err.String())
 		}
 		return nil
 	}

 	for _, file := range p.Files.Values() {
 		if err := walk(file, []FileInclude{}); err != nil {
 			return err
 		}
 	}
 	return nil

 }

 // checkForCycles ensures that the graph of target dependencies are acyclic (a DAG)
 func checkForCycles(p *Project) error {
 	type state int
 	const (
 		unvisited state = iota
 		visiting
 		checked
 	)

 	cache := container.NewMap[TargetName, state]()

 	var walk func(t *Target, path []TargetName) error
 	walk = func(t *Target, path []TargetName) error {
 		switch cache[t.Name] {
 		case unvisited:
 			cache[t.Name] = visiting
 			for _, dep := range t.Dependencies.Internal() {
 				if err := walk(dep, append(path, dep.Name)); err != nil {
 					return err
 				}
 			}
 			cache[t.Name] = checked
 		case visiting:
 			err := strings.Builder{}
 			fmt.Fprintln(&err, "cyclic target dependency found:")
 			for _, t := range path {
 				fmt.Fprintln(&err, "  ", string(t))
 			}
 			fmt.Fprintln(&err, "  ", string(t.Name))
 			return fmt.Errorf(err.String())
 		}
 		return nil
 	}

 	for _, target := range p.Targets.Values() {
 		if err := walk(target, []TargetName{target.Name}); err != nil {
 			return err
 		}
 	}
 	return nil
 }

 // emitBuildFiles emits a 'BUILD.*' file in each source directory for each
 // 'BUILD.*.tmpl' found in this directory.
 func emitBuildFiles(p *Project) error {
 	// Glob all the template files
 	templatePaths, err := glob.Glob(path.Join(fileutils.ThisDir(), "*.tmpl"))
 	if err != nil {
 		return err
 	}
 	if len(templatePaths) == 0 {
 		return fmt.Errorf("no template files found")
 	}

 	// Load the templates
 	templates := container.NewMap[string, *template.Template]()
 	for _, path := range templatePaths {
 		tmpl, err := template.FromFile(path)
 		if err != nil {
 			return err
 		}
 		templates[path] = tmpl
 	}

 	// process executes all the templates for the directory dir
 	// This is run concurrently, so must not modify shared state
 	process := func(dir *Directory) (common.StaleFiles, error) {
 		stale := common.StaleFiles{}

 		// For each template...
 		for _, tmplPath := range templatePaths {
 			_, tmplName := filepath.Split(tmplPath)
 			outputName := strings.TrimSuffix(tmplName, ".tmpl")
 			outputPath := path.Join(dir.AbsPath(), outputName)

 			// Attempt to read the existing output file
 			existing, err := os.ReadFile(outputPath)
 			if err != nil {
 				existing = nil
 			}
 			// If the file is annotated with a GEN_BUILD:DO_NOT_GENERATE directive, leave it alone
 			if reDoNotGenerate.Match(existing) {
 				continue
 			}
 			// Buffer for output
 			w := &bytes.Buffer{}

 			// Write the header
 			relTmplPath, err := filepath.Rel(fileutils.DawnRoot(), tmplPath)
 			if err != nil {
 				return nil, err
 			}
 			w.WriteString(common.Header(string(existing), CanonicalizePath(relTmplPath), "#"))

 			// Write the template output
 			err = templates[tmplPath].Run(w, dir, map[string]any{})
 			if err != nil {
 				return nil, err
 			}

 			// Format the output if it's a GN file.
 			if path.Ext(outputName) == ".gn" {
 				unformatted := w.String()
 				gn := exec.Command("gn", "format", "--stdin")
 				gn.Stdin = bytes.NewReader([]byte(unformatted))
 				w.Reset()
 				gn.Stdout = w
 				gn.Stderr = w
 				if err := gn.Run(); err != nil {
 					return nil, fmt.Errorf("%v\ngn format failed: %w\n%v", unformatted, err, w.String())
 				}
 			}

 			if string(existing) != w.String() {
 				stale = append(stale, outputPath)
 			}

 			if !p.cfg.Flags.CheckStale {
 				if err := os.WriteFile(outputPath, w.Bytes(), 0666); err != nil {
 					return nil, err
 				}
 			}

 		}

 		return stale, nil
 	}

 	// Concurrently run process() on all the directories.
 	staleLists, err := transform.GoSlice(p.Directories.Values(), process)
 	if err != nil {
 		return err
 	}

 	if p.cfg.Flags.Verbose || p.cfg.Flags.CheckStale {
 		// Collect all stale files into a flat list
 		stale := transform.Flatten(staleLists)
 		if p.cfg.Flags.CheckStale && len(stale) > 0 {
 			return stale
 		}
 		if p.cfg.Flags.Verbose {
 			log.Printf("generated %v files\n", len(stale))
 		}
 	}

 	return nil
 }

 // targetKindFromFilename returns the target kind my pattern matching the filename
 func targetKindFromFilename(filename string) TargetKind {
 	switch {
 	case strings.HasSuffix(filename, "_test.cc"), strings.HasSuffix(filename, "_test.h"):
 		return targetTest
 	case strings.HasSuffix(filename, "_bench.cc"), strings.HasSuffix(filename, "_bench.h"):
 		return targetBench
 	case filename == "main.cc":
 		return targetCmd
 	case strings.HasSuffix(filename, ".cc"), strings.HasSuffix(filename, ".h"):
 		return targetLib
 	}
 	return targetInvalid
 }

 // emitDotFile writes a GraphViz DOT file visualizing the target dependency graph
 func emitDotFile(p *Project, kind TargetKind) error {
 	g := graphviz.Graph{}
 	nodes := container.NewMap[TargetName, int]()
 	targets := []*Target{}
 	for _, target := range p.Targets.Values() {
 		if target.Kind == kind {
 			targets = append(targets, target)
 		}
 	}
 	for _, target := range targets {
 		nodes.Add(target.Name, g.AddNode(string(target.Name)))
 	}
 	for _, target := range targets {
 		for _, dep := range target.Dependencies.Internal() {
 			g.AddEdge(nodes[target.Name], nodes[dep.Name], "")
 		}
 	}

 	g.MakeDirected()

 	g.DefaultNodeAttribute(graphviz.Shape, graphviz.ShapeBox)
 	g.DefaultNodeAttribute(graphviz.FontName, "Courier")
 	g.DefaultNodeAttribute(graphviz.FontSize, "14")
 	g.DefaultNodeAttribute(graphviz.Style, graphviz.StyleFilled+","+graphviz.StyleRounded)
 	g.DefaultNodeAttribute(graphviz.FillColor, "yellow")

 	g.DefaultEdgeAttribute(graphviz.FontName, "Courier")
 	g.DefaultEdgeAttribute(graphviz.FontSize, "12")

 	file, err := os.Create(path.Join(p.Root, fmt.Sprintf("%v.dot", kind)))
 	if err != nil {
 		return err
 	}
 	defer file.Close()

 	g.GenerateDOT(file)
 	return nil
 }

 var (
 	// Regular expressions used by this file
 	reInclude       = regexp.MustCompile(`\s*#\s*include\s*\"([^"]+)\"`)
 	reIgnoreInclude = regexp.MustCompile(`//\s*GEN_BUILD:IGNORE`)
 	reCondition     = regexp.MustCompile(`//\s*GEN_BUILD:CONDITION\((.*)\)\s*$`)
 	reDoNotGenerate = regexp.MustCompile(`#\s*GEN_BUILD:DO_NOT_GENERATE`)
 )
	// Copyright 2023 The Tint Authors.
	//
	// 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 implements a extensible build file list and module dependency
	// generator for Tint.
	// See: docs/tint/gen.md
	package build

	import (
	"bytes"
	"context"
	"encoding/json"
	"flag"
	"fmt"
	"log"
	"os"
	"os/exec"
	"path"
	"path/filepath"
	"regexp"
	"strings"

	"dawn.googlesource.com/dawn/tools/src/cmd/gen/common"
	"dawn.googlesource.com/dawn/tools/src/container"
	"dawn.googlesource.com/dawn/tools/src/fileutils"
	"dawn.googlesource.com/dawn/tools/src/glob"
	"dawn.googlesource.com/dawn/tools/src/match"
	"dawn.googlesource.com/dawn/tools/src/template"
	"dawn.googlesource.com/dawn/tools/src/transform"
	"github.com/mzohreva/gographviz/graphviz"
	"github.com/tidwall/jsonc"
	)

	const srcTint = "src/tint"

	func init() {
	common.Register(&Cmd{})
	}

	type Cmd struct {
	flags struct {
	dot bool
	}
	}

	func (Cmd) Name() string {
	return "build"
	}

	func (Cmd) Desc() string {
	return `build generates BUILD.* files in each of Tint's source directories`
	}

	func (c Cmd) RegisterFlags(ctx context.Context, cfg common.Config) ([]string, error) {
	flag.BoolVar(&c.flags.dot, "dot", false, "emit GraphViz DOT files for each target kind")
	return nil, nil
	}

	func (c Cmd) Run(ctx context.Context, cfg *common.Config) error {
	p := NewProject(CanonicalizePath(path.Join(fileutils.DawnRoot(), srcTint)), cfg)

	for _, stage := range []struct {
	desc string
	fn func(p *Project) error
	}{
	{"loading 'externals.json'", loadExternals},
	{"populating source files", populateSourceFiles},
	{"scanning source files", scanSourceFiles},
	{"loading directory configs", applyDirectoryConfigs},
	{"building dependencies", buildDependencies},
	{"checking for cycles", checkForCycles},
	{"emitting build files", emitBuildFiles},
	} {
	if cfg.Flags.Verbose {
	log.Printf("%v...\n", stage.desc)
	}
	if err := stage.fn(p); err != nil {
	return err
	}
	}

	if c.flags.dot {
	for _, kind := range AllTargetKinds {
	if err := emitDotFile(p, kind); err != nil {
	return err
	}
	}
	}

	if cfg.Flags.Verbose {
	log.Println("done")
	}
	return nil
	}

	// loadExternals loads the 'externals.json' file in this directory.
	func loadExternals(p *Project) error {
	content, err := os.ReadFile(path.Join(fileutils.ThisDir(), "externals.json"))
	if err != nil {
	return err
	}

	externals := container.NewMap[string, struct {
	IncludePattern string `json:"include_pattern"`
	Condition string
	}]()
	if err := json.Unmarshal(jsonc.ToJSON(content), &externals); err != nil {
	return fmt.Errorf("failed to parse 'externals.json': %w", err)
	}

	for _, name := range externals.Keys() {
	external := externals[name]
	match, err := match.New(external.IncludePattern)
	if err != nil {
	return fmt.Errorf("'externals.json' matcher error: %w", err)
	}
	name := ExternalDependencyName(name)
	p.externals.Add(name, ExternalDependency{
	Name: name,
	Condition: external.Condition,
	includePatternMatch: match,
	})
	}

	return nil
	}

	// Globs all the source files, and creates populates the Project with Directory, Target and File.
	// File name patterns are used to bin each file into a target for the directory.
	func populateSourceFiles(p *Project) error {
	paths, err := glob.Scan(p.Root, glob.MustParseConfig(`{
	"paths": [
	{
	"include": [
	"/*.cc",
	"/*.h",
	"/*.inl"
	]
	},
	{
	"exclude": [
	"fuzzers/**"
	]
	}]
	}`))
	if err != nil {
	return err
	}

	for _, filepath := range paths {
	filepath = CanonicalizePath(filepath)
	dir, name := path.Split(filepath)
	if kind := targetKindFromFilename(name); kind != targetInvalid {
	directory := p.AddDirectory(dir)
	p.AddTarget(directory, kind).AddSourceFile(p.AddFile(filepath))
	}
	}

	return nil
	}

	// scanSourceFiles scans all the source files for:
	// * #includes to build a dependencies between targets
	// * 'GEN_BUILD:' directives
	func scanSourceFiles(p *Project) error {
	// ParsedFile describes all the includes and conditions found in a source file
	type ParsedFile struct {
	conditions []string
	includes []Include
	}

	// parseFile parses the source file at 'path' represented by 'file'
	// As this is run concurrently, it must not modify any shared state (including file)
	parseFile := func(path string, file File) (string, ParsedFile, error) {
	body, err := os.ReadFile(file.AbsPath())
	if err != nil {
	return path, nil, err
	}
	out := &ParsedFile{}
	for i, line := range strings.Split(string(body), "\n") {
	if match := reCondition.FindStringSubmatch(line); len(match) > 0 {
	out.conditions = append(out.conditions, match[1])
	}
	if !reIgnoreInclude.MatchString(line) {
	if match := reInclude.FindStringSubmatch(line); len(match) > 0 {
	out.includes = append(out.includes, Include{match[1], i + 1})
	}
	}
	}
	return path, out, nil
	}

	// Create a new map by calling parseFile() on each entry of p.Files
	// This is performed over multiple concurrent goroutines.
	parsedFiles, err := transform.GoMap(p.Files, parseFile)
	if err != nil {
	return err
	}

	// For each file, of each target, of each directory...
	for _, dir := range p.Directories {
	for _, target := range dir.Targets() {
	for _, file := range target.SourceFiles() {
	// Retrieve the parsed file information
	parsed := parsedFiles[file.Path()]

	// Apply any conditions
	for _, condition := range parsed.conditions {
	if file.Condition == "" {
	file.Condition = condition
	} else {
	file.Condition += " && " + condition
	}
	}

	file.Includes = append(file.Includes, parsed.includes...)
	}
	}
	}
	return nil
	}

	// applyDirectoryConfigs loads a 'BUILD.cfg' file in each source directory (if found), and
	// applies the config to the Directory and/or Targets.
	func applyDirectoryConfigs(p *Project) error {
	// Config for a single target of a directory
	type TargetConfig struct {
	AdditionalDependencies []string
	}
	// Config for a directory
	type DirectoryConfig struct {
	// Condition for all targets in the directory
	Condition string
	// Configuration for the 'lib' target
	Lib TargetConfig
	// Configuration for the 'test' target
	Test TargetConfig
	// Configuration for the 'bench' target
	Bench TargetConfig
	// Configuration for the 'cmd' target
	Cmd TargetConfig
	}

	// For each directory in the project...
	for _, dir := range p.Directories.Values() {
	path := path.Join(dir.AbsPath(), "BUILD.cfg")
	content, err := os.ReadFile(path)
	if err != nil {
	continue
	}

	// Parse the config
	cfg := DirectoryConfig{}
	if err := json.Unmarshal(jsonc.ToJSON(content), &cfg); err != nil {
	return fmt.Errorf("error while parsing '%v': %w", path, err)
	}

	// Apply any directory-level condition
	for _, target := range dir.Targets() {
	target.Condition = cfg.Condition
	}

	// For each target config...
	for _, tc := range []struct {
	cfg *TargetConfig
	kind TargetKind
	}{
	{&cfg.Lib, targetLib},
	{&cfg.Test, targetTest},
	{&cfg.Bench, targetBench},
	{&cfg.Cmd, targetCmd},
	} {
	// Add any additional dependencies
	for _, depPattern := range tc.cfg.AdditionalDependencies {
	match, err := match.New(depPattern)
	if err != nil {
	return fmt.Errorf("%v: failed to parse %v.AdditionalDependencies '%v': %w", path, tc.kind, depPattern, err)
	}
	additionalDeps := []*Target{}
	for _, target := range p.Targets.Keys() {
	if match(string(target)) {
	additionalDeps = append(additionalDeps, p.Targets[target])
	}
	}
	if len(additionalDeps) == 0 {
	return fmt.Errorf("%v: %v.AdditionalDependencies '%v' did not match any targets", path, tc.kind, depPattern)
	}
	target := p.AddTarget(dir, tc.kind)
	for _, dep := range additionalDeps {
	if dep != target {
	target.Dependencies.AddInternal(dep)
	}
	}
	}
	}
	}

	return nil
	}

	// buildDependencies walks all the #includes in all files, building the dependency information for
	// all targets and files in the project. Errors if any cyclic includes are found.
	func buildDependencies(p *Project) error {
	type state int
	const (
	unvisited state = iota
	visiting
	checked
	)

	cache := container.NewMap[string, state]()

	type FileInclude struct {
	file string
	inc Include
	}

	var walk func(file *File, route []FileInclude) error
	walk = func(file *File, route []FileInclude) error {
	// Adds the dependency to the file and target's list of internal dependencies
	addInternalDependency := func(dep *Target) {
	file.TransitiveDependencies.AddInternal(dep)
	if file.Target != dep {
	file.Target.Dependencies.AddInternal(dep)
	}
	}
	// Adds the dependency to the file and target's list of external dependencies
	addExternalDependency := func(dep ExternalDependency) {
	file.TransitiveDependencies.AddExternal(dep)
	file.Target.Dependencies.AddExternal(dep)
	}

	filePath := file.Path()
	switch cache[filePath] {
	case unvisited:
	cache[filePath] = visiting

	for _, include := range file.Includes {
	if strings.HasPrefix(include.Path, srcTint) {
	// #include "src/tint/..."
	path := include.Path[len(srcTint)+1:] // Strip 'src/tint/'

	includeFile := p.File(path)
	if includeFile == nil {
	return fmt.Errorf(`%v:%v includes non-existent file '%v'`, file.Path(), include.Line, path)
	}

	if file.Target.Kind == targetLib && includeFile.Target.Kind != targetLib {
	return fmt.Errorf(`%v:%v lib target must not include %v target`, file.Path(), include.Line, includeFile.Target.Kind)
	}

	addInternalDependency(includeFile.Target)

	// Gather the dependencies for the included file
	if err := walk(includeFile, append(route, FileInclude{file: file.Path(), inc: include})); err != nil {
	return err
	}

	for _, dependency := range includeFile.TransitiveDependencies.Internal() {
	addInternalDependency(dependency)
	}
	for _, dependency := range includeFile.TransitiveDependencies.External() {
	addExternalDependency(dependency)
	}

	} else {
	// Check for external includes
	for _, external := range p.externals.Values() {
	if external.includePatternMatch(include.Path) {
	addExternalDependency(external)
	}
	}
	}

	}

	cache[filePath] = checked

	case visiting:
	err := strings.Builder{}
	fmt.Fprintln(&err, "cyclic include found:")
	for _, include := range route {
	fmt.Fprintf(&err, " %v:%v includes '%v'\n", include.file, include.inc.Line, include.inc.Path)
	}
	return fmt.Errorf(err.String())
	}
	return nil
	}

	for _, file := range p.Files.Values() {
	if err := walk(file, []FileInclude{}); err != nil {
	return err
	}
	}
	return nil

	}

	// checkForCycles ensures that the graph of target dependencies are acyclic (a DAG)
	func checkForCycles(p *Project) error {
	type state int
	const (
	unvisited state = iota
	visiting
	checked
	)

	cache := container.NewMap[TargetName, state]()

	var walk func(t *Target, path []TargetName) error
	walk = func(t *Target, path []TargetName) error {
	switch cache[t.Name] {
	case unvisited:
	cache[t.Name] = visiting
	for _, dep := range t.Dependencies.Internal() {
	if err := walk(dep, append(path, dep.Name)); err != nil {
	return err
	}
	}
	cache[t.Name] = checked
	case visiting:
	err := strings.Builder{}
	fmt.Fprintln(&err, "cyclic target dependency found:")
	for _, t := range path {
	fmt.Fprintln(&err, " ", string(t))
	}
	fmt.Fprintln(&err, " ", string(t.Name))
	return fmt.Errorf(err.String())
	}
	return nil
	}

	for _, target := range p.Targets.Values() {
	if err := walk(target, []TargetName{target.Name}); err != nil {
	return err
	}
	}
	return nil
	}

	// emitBuildFiles emits a 'BUILD.*' file in each source directory for each
	// 'BUILD.*.tmpl' found in this directory.
	func emitBuildFiles(p *Project) error {
	// Glob all the template files
	templatePaths, err := glob.Glob(path.Join(fileutils.ThisDir(), "*.tmpl"))
	if err != nil {
	return err
	}
	if len(templatePaths) == 0 {
	return fmt.Errorf("no template files found")
	}

	// Load the templates
	templates := container.NewMap[string, *template.Template]()
	for _, path := range templatePaths {
	tmpl, err := template.FromFile(path)
	if err != nil {
	return err
	}
	templates[path] = tmpl
	}

	// process executes all the templates for the directory dir
	// This is run concurrently, so must not modify shared state
	process := func(dir *Directory) (common.StaleFiles, error) {
	stale := common.StaleFiles{}

	// For each template...
	for _, tmplPath := range templatePaths {
	_, tmplName := filepath.Split(tmplPath)
	outputName := strings.TrimSuffix(tmplName, ".tmpl")
	outputPath := path.Join(dir.AbsPath(), outputName)

	// Attempt to read the existing output file
	existing, err := os.ReadFile(outputPath)
	if err != nil {
	existing = nil
	}
	// If the file is annotated with a GEN_BUILD:DO_NOT_GENERATE directive, leave it alone
	if reDoNotGenerate.Match(existing) {
	continue
	}
	// Buffer for output
	w := &bytes.Buffer{}

	// Write the header
	relTmplPath, err := filepath.Rel(fileutils.DawnRoot(), tmplPath)
	if err != nil {
	return nil, err
	}
	w.WriteString(common.Header(string(existing), CanonicalizePath(relTmplPath), "#"))

	// Write the template output
	err = templates[tmplPath].Run(w, dir, map[string]any{})
	if err != nil {
	return nil, err
	}

	// Format the output if it's a GN file.
	if path.Ext(outputName) == ".gn" {
	unformatted := w.String()
	gn := exec.Command("gn", "format", "--stdin")
	gn.Stdin = bytes.NewReader([]byte(unformatted))
	w.Reset()
	gn.Stdout = w
	gn.Stderr = w
	if err := gn.Run(); err != nil {
	return nil, fmt.Errorf("%v\ngn format failed: %w\n%v", unformatted, err, w.String())
	}
	}

	if string(existing) != w.String() {
	stale = append(stale, outputPath)
	}

	if !p.cfg.Flags.CheckStale {
	if err := os.WriteFile(outputPath, w.Bytes(), 0666); err != nil {
	return nil, err
	}
	}

	}

	return stale, nil
	}

	// Concurrently run process() on all the directories.
	staleLists, err := transform.GoSlice(p.Directories.Values(), process)
	if err != nil {
	return err
	}

	if p.cfg.Flags.Verbose \|\| p.cfg.Flags.CheckStale {
	// Collect all stale files into a flat list
	stale := transform.Flatten(staleLists)
	if p.cfg.Flags.CheckStale && len(stale) > 0 {
	return stale
	}
	if p.cfg.Flags.Verbose {
	log.Printf("generated %v files\n", len(stale))
	}
	}

	return nil
	}

	// targetKindFromFilename returns the target kind my pattern matching the filename
	func targetKindFromFilename(filename string) TargetKind {
	switch {
	case strings.HasSuffix(filename, "_test.cc"), strings.HasSuffix(filename, "_test.h"):
	return targetTest
	case strings.HasSuffix(filename, "_bench.cc"), strings.HasSuffix(filename, "_bench.h"):
	return targetBench
	case filename == "main.cc":
	return targetCmd
	case strings.HasSuffix(filename, ".cc"), strings.HasSuffix(filename, ".h"):
	return targetLib
	}
	return targetInvalid
	}

	// emitDotFile writes a GraphViz DOT file visualizing the target dependency graph
	func emitDotFile(p *Project, kind TargetKind) error {
	g := graphviz.Graph{}
	nodes := container.NewMap[TargetName, int]()
	targets := []*Target{}
	for _, target := range p.Targets.Values() {
	if target.Kind == kind {
	targets = append(targets, target)
	}
	}
	for _, target := range targets {
	nodes.Add(target.Name, g.AddNode(string(target.Name)))
	}
	for _, target := range targets {
	for _, dep := range target.Dependencies.Internal() {
	g.AddEdge(nodes[target.Name], nodes[dep.Name], "")
	}
	}

	g.MakeDirected()

	g.DefaultNodeAttribute(graphviz.Shape, graphviz.ShapeBox)
	g.DefaultNodeAttribute(graphviz.FontName, "Courier")
	g.DefaultNodeAttribute(graphviz.FontSize, "14")
	g.DefaultNodeAttribute(graphviz.Style, graphviz.StyleFilled+","+graphviz.StyleRounded)
	g.DefaultNodeAttribute(graphviz.FillColor, "yellow")

	g.DefaultEdgeAttribute(graphviz.FontName, "Courier")
	g.DefaultEdgeAttribute(graphviz.FontSize, "12")

	file, err := os.Create(path.Join(p.Root, fmt.Sprintf("%v.dot", kind)))
	if err != nil {
	return err
	}
	defer file.Close()

	g.GenerateDOT(file)
	return nil
	}

	var (
	// Regular expressions used by this file
	reInclude = regexp.MustCompile(`\s#\sinclude\s*\"([^"]+)\"`)
	reIgnoreInclude = regexp.MustCompile(`//\s*GEN_BUILD:IGNORE`)
	reCondition = regexp.MustCompile(`//\sGEN_BUILD:CONDITION\((.)\)\s*$`)
	reDoNotGenerate = regexp.MustCompile(`#\s*GEN_BUILD:DO_NOT_GENERATE`)
	)