fix: write logs to stderr instead of stdout, fixes #753 (#759)

.version

@@ -1 +1 @@
-0.2.707
+0.2.708

cmd/templ/fmtcmd/main.go

@@ -11,45 +11,26 @@ import (
 	"time"
 
 	"github.com/a-h/templ/cmd/templ/processor"
-	"github.com/a-h/templ/cmd/templ/sloghandler"
 	parser "github.com/a-h/templ/parser/v2"
 	"github.com/natefinch/atomic"
 )
 
 type Arguments struct {
 	ToStdout    bool
 	Files       []string
-	LogLevel    string
 	WorkerCount int
 }
 
-func Run(w io.Writer, args Arguments) (err error) {
+func Run(log *slog.Logger, stdin io.Reader, stdout io.Writer, args Arguments) (err error) {
 	// If no files are provided, read from stdin and write to stdout.
 	if len(args.Files) == 0 {
-		return format(writeToStdout, readFromStdin)
-	}
-
-	level := slog.LevelInfo.Level()
-	switch args.LogLevel {
-	case "debug":
-		level = slog.LevelDebug.Level()
-	case "warn":
-		level = slog.LevelWarn.Level()
-	case "error":
-		level = slog.LevelError.Level()
-	}
-	log := slog.New(sloghandler.NewHandler(w, &slog.HandlerOptions{
-		AddSource: args.LogLevel == "debug",
-		Level:     level,
-	}))
-	if args.ToStdout {
-		log = slog.New(slog.NewTextHandler(io.Discard, &slog.HandlerOptions{}))
+		return format(writeToWriter(stdout), readFromReader(stdin))
 	}
 	process := func(fileName string) error {
 		read := readFromFile(fileName)
 		write := writeToFile
 		if args.ToStdout {
-			write = writeToStdout
+			write = writeToWriter(stdout)
 		}
 		return format(write, read)
 	}
@@ -101,12 +82,14 @@ func (f *Formatter) Run() (err error) {
 
 type reader func() (fileName, src string, err error)
 
-func readFromStdin() (fileName, src string, err error) {
-	b, err := io.ReadAll(os.Stdin)
-	if err != nil {
-		return "", "", fmt.Errorf("failed to read stdin: %w", err)
+func readFromReader(r io.Reader) func() (fileName, src string, err error) {
+	return func() (fileName, src string, err error) {
+		b, err := io.ReadAll(r)
+		if err != nil {
+			return "", "", fmt.Errorf("failed to read stdin: %w", err)
+		}
+		return "stdin.templ", string(b), nil
 	}
-	return "stdin.templ", string(b), nil
 }
 
 func readFromFile(name string) reader {
@@ -123,11 +106,13 @@ type writer func(fileName, tgt string) error
 
 var mu sync.Mutex
 
-func writeToStdout(fileName, tgt string) error {
-	mu.Lock()
-	defer mu.Unlock()
-	_, err := os.Stdout.Write([]byte(tgt))
-	return err
+func writeToWriter(w io.Writer) func(fileName, tgt string) error {
+	return func(fileName, tgt string) error {
+		mu.Lock()
+		defer mu.Unlock()
+		_, err := w.Write([]byte(tgt))
+		return err
+	}
 }
 
 func writeToFile(fileName, tgt string) error {

cmd/templ/generatecmd/cmd.go

@@ -4,7 +4,6 @@ import (
 	"context"
 	"errors"
 	"fmt"
-	"io"
 	"log/slog"
 	"net/http"
 	"net/url"
@@ -55,9 +54,14 @@ func (cmd Generate) Run(ctx context.Context) (err error) {
 	if cmd.Args.Watch && cmd.Args.FileName != "" {
 		return fmt.Errorf("cannot watch a single file, remove the -f or -watch flag")
 	}
-	if cmd.Args.FileName == "" && cmd.Args.ToStdout {
+	writingToWriter := cmd.Args.FileWriter != nil
+	if cmd.Args.FileName == "" && writingToWriter {
 		return fmt.Errorf("only a single file can be output to stdout, add the -f flag to specify the file to generate code for")
 	}
+	// Default to writing to files.
+	if cmd.Args.FileWriter == nil {
+		cmd.Args.FileWriter = FileWriter
+	}
 	if cmd.Args.PPROFPort > 0 {
 		go func() {
 			_ = http.ListenAndServe(fmt.Sprintf("localhost:%d", cmd.Args.PPROFPort), nil)
@@ -81,10 +85,6 @@ func (cmd Generate) Run(ctx context.Context) (err error) {
 		opts = append(opts, generator.WithTimestamp(time.Now()))
 	}
 
-	if cmd.Args.ToStdout {
-		cmd.Log = slog.New(slog.NewTextHandler(io.Discard, &slog.HandlerOptions{}))
-	}
-
 	// Check the version of the templ module.
 	if err := modcheck.Check(cmd.Args.Path); err != nil {
 		cmd.Log.Warn("templ version check: " + err.Error())
@@ -97,7 +97,7 @@ func (cmd Generate) Run(ctx context.Context) (err error) {
 		opts,
 		cmd.Args.GenerateSourceMapVisualisations,
 		cmd.Args.KeepOrphanedFiles,
-		cmd.Args.ToStdout,
+		cmd.Args.FileWriter,
 	)
 
 	// If we're processing a single file, don't bother setting up the channels/multithreaing.
@@ -182,7 +182,7 @@ func (cmd Generate) Run(ctx context.Context) (err error) {
 			opts,
 			cmd.Args.GenerateSourceMapVisualisations,
 			cmd.Args.KeepOrphanedFiles,
-			cmd.Args.ToStdout,
+			cmd.Args.FileWriter,
 		)
 		errorCount.Store(0)
 		if err := watcher.WalkFiles(ctx, cmd.Args.Path, events); err != nil {

cmd/templ/generatecmd/eventhandler.go

@@ -9,6 +9,7 @@ import (
 	"go/format"
 	"go/scanner"
 	"go/token"
+	"io"
 	"log/slog"
 	"os"
 	"path"
@@ -23,14 +24,27 @@ import (
 	"github.com/fsnotify/fsnotify"
 )
 
+type FileWriterFunc func(name string, contents []byte) error
+
+func FileWriter(fileName string, contents []byte) error {
+	return os.WriteFile(fileName, contents, 0o644)
+}
+
+func WriterFileWriter(w io.Writer) FileWriterFunc {
+	return func(_ string, contents []byte) error {
+		_, err := w.Write(contents)
+		return err
+	}
+}
+
 func NewFSEventHandler(
 	log *slog.Logger,
 	dir string,
 	devMode bool,
 	genOpts []generator.GenerateOpt,
 	genSourceMapVis bool,
 	keepOrphanedFiles bool,
-	toStdout bool,
+	fileWriter FileWriterFunc,
 ) *FSEventHandler {
 	if !path.IsAbs(dir) {
 		dir, _ = filepath.Abs(dir)
@@ -48,10 +62,7 @@ func NewFSEventHandler(
 		genSourceMapVis:            genSourceMapVis,
 		DevMode:                    devMode,
 		keepOrphanedFiles:          keepOrphanedFiles,
-		writer:                     writeToFile,
-	}
-	if toStdout {
-		fseh.writer = writeToStdout
+		writer:                     fileWriter,
 	}
 	if devMode {
 		fseh.genOpts = append(fseh.genOpts, generator.WithExtractStrings())
@@ -77,15 +88,6 @@ type FSEventHandler struct {
 	writer                     func(string, []byte) error
 }
 
-func writeToFile(fileName string, contents []byte) error {
-	return os.WriteFile(fileName, contents, 0o644)
-}
-
-func writeToStdout(_ string, contents []byte) error {
-	_, err := os.Stdout.Write(contents)
-	return err
-}
-
 func (h *FSEventHandler) HandleEvent(ctx context.Context, event fsnotify.Event) (goUpdated, textUpdated bool, err error) {
 	// Handle _templ.go files.
 	if !event.Has(fsnotify.Remove) && strings.HasSuffix(event.Name, "_templ.go") {
@@ -223,8 +225,8 @@ func (h *FSEventHandler) generate(ctx context.Context, fileName string) (goUpdat
 
 	formattedGoCode, err := format.Source(b.Bytes())
 	if err != nil {
-		err = remapErrorList(err, sourceMap, fileName, targetFileName)
-		return false, false, nil, fmt.Errorf("%s source formatting error %w", fileName, err)
+		err = remapErrorList(err, sourceMap, fileName)
+		return false, false, nil, fmt.Errorf("% source formatting error %w", fileName, err)
 	}
 
 	// Hash output, and write out the file if the goCodeHash has changed.
@@ -262,7 +264,7 @@ func (h *FSEventHandler) generate(ctx context.Context, fileName string) (goUpdat
 
 // Takes an error from the formatter and attempts to convert the positions reported in the target file to their positions
 // in the source file.
-func remapErrorList(err error, sourceMap *parser.SourceMap, fileName string, targetFileName string) error {
+func remapErrorList(err error, sourceMap *parser.SourceMap, fileName string) error {
 	list, ok := err.(scanner.ErrorList)
 	if !ok || len(list) == 0 {
 		return err

cmd/templ/generatecmd/main.go

@@ -3,17 +3,14 @@ package generatecmd
 import (
 	"context"
 	_ "embed"
-	"io"
 	"log/slog"
 
 	_ "net/http/pprof"
-
-	"github.com/a-h/templ/cmd/templ/sloghandler"
 )
 
 type Arguments struct {
 	FileName                        string
-	ToStdout                        bool
+	FileWriter                      FileWriterFunc
 	Path                            string
 	Watch                           bool
 	OpenBrowser                     bool
@@ -26,25 +23,11 @@ type Arguments struct {
 	GenerateSourceMapVisualisations bool
 	IncludeVersion                  bool
 	IncludeTimestamp                bool
-	LogLevel                        string
 	// PPROFPort is the port to run the pprof server on.
 	PPROFPort         int
 	KeepOrphanedFiles bool
 }
 
-func Run(ctx context.Context, w io.Writer, args Arguments) (err error) {
-	level := slog.LevelInfo.Level()
-	switch args.LogLevel {
-	case "debug":
-		level = slog.LevelDebug.Level()
-	case "warn":
-		level = slog.LevelWarn.Level()
-	case "error":
-		level = slog.LevelError.Level()
-	}
-	log := slog.New(sloghandler.NewHandler(w, &slog.HandlerOptions{
-		AddSource: args.LogLevel == "debug",
-		Level:     level,
-	}))
+func Run(ctx context.Context, log *slog.Logger, args Arguments) (err error) {
 	return NewGenerate(log, args).Run(ctx)
 }

cmd/templ/generatecmd/test-eventhandler/eventhandler_test.go

@@ -42,7 +42,8 @@ func TestErrorLocationMapping(t *testing.T) {
 	}
 
 	slog := slog.New(slog.NewTextHandler(io.Discard, &slog.HandlerOptions{}))
-	fseh := generatecmd.NewFSEventHandler(slog, ".", false, []generator.GenerateOpt{}, false, false, true)
+	var fw generatecmd.FileWriterFunc
+	fseh := generatecmd.NewFSEventHandler(slog, ".", false, []generator.GenerateOpt{}, false, false, fw)
 	for _, test := range tests {
 		// The raw files cannot end in .templ because they will cause the generator to fail. Instead,
 		// we create a tmp file that ends in .templ only for the duration of the test.

cmd/templ/generatecmd/testwatch/generate_test.go

@@ -6,6 +6,8 @@ import (
 	"context"
 	"embed"
 	"fmt"
+	"io"
+	"log/slog"
 	"net"
 	"net/http"
 	"os"
@@ -368,16 +370,23 @@ func Setup(gzipEncoding bool) (args TestArgs, teardown func(t *testing.T), err e
 			command += " -gzip true"
 		}
 
-		cmdErr = generatecmd.Run(ctx, os.Stdout, generatecmd.Arguments{
-			Path:              appDir,
-			Watch:             true,
-			Command:           command,
-			ProxyBind:         proxyBind,
-			ProxyPort:         proxyPort,
-			Proxy:             args.AppURL,
-			IncludeVersion:    false,
-			IncludeTimestamp:  false,
-			KeepOrphanedFiles: false,
+		log := slog.New(slog.NewJSONHandler(io.Discard, nil))
+
+		cmdErr = generatecmd.Run(ctx, log, generatecmd.Arguments{
+			Path:                            appDir,
+			Watch:                           true,
+			OpenBrowser:                     false,
+			Command:                         command,
+			ProxyBind:                       proxyBind,
+			ProxyPort:                       proxyPort,
+			Proxy:                           args.AppURL,
+			NotifyProxy:                     false,
+			WorkerCount:                     0,
+			GenerateSourceMapVisualisations: false,
+			IncludeVersion:                  false,
+			IncludeTimestamp:                false,
+			PPROFPort:                       0,
+			KeepOrphanedFiles:               false,
 		})
 	}()
 
@@ -460,8 +469,10 @@ func TestGenerateReturnsErrors(t *testing.T) {
 		t.Errorf("failed to replace text in file: %v", err)
 	}
 
+	log := slog.New(slog.NewJSONHandler(io.Discard, nil))
+
 	// Run.
-	err = generatecmd.Run(context.Background(), os.Stdout, generatecmd.Arguments{
+	err = generatecmd.Run(context.Background(), log, generatecmd.Arguments{
 		Path:              appDir,
 		Watch:             false,
 		IncludeVersion:    false,

cmd/templ/lspcmd/main.go

@@ -29,7 +29,7 @@ type Arguments struct {
 	HTTPDebug string
 }
 
-func Run(w io.Writer, args Arguments) (err error) {
+func Run(stdin io.Reader, stdout, stderr io.Writer, args Arguments) (err error) {
 	ctx := context.Background()
 	ctx, cancel := context.WithCancel(ctx)
 	signalChan := make(chan os.Signal, 1)
@@ -61,14 +61,14 @@ func Run(w io.Writer, args Arguments) (err error) {
 		}
 		log, err = cfg.Build()
 		if err != nil {
-			_, _ = fmt.Fprintf(w, "failed to create logger: %v\n", err)
+			_, _ = fmt.Fprintf(stderr, "failed to create logger: %v\n", err)
 			os.Exit(1)
 		}
 	}
 	defer func() {
 		_ = log.Sync()
 	}()
-	templStream := jsonrpc2.NewStream(newStdRwc(log, "templStream", w, os.Stdin))
+	templStream := jsonrpc2.NewStream(newStdRwc(log, "templStream", stdout, stdin))
 	return run(ctx, log, templStream, args)
 }