Refactor: replace os.IsNotExist() with errors.Is(err, fs.ErrNotExist()

`os.IsNotExist()` is from before `errors.Is()` existed. The latter is the
recommended approach, as it also recognised wrapped errors.

No functional changes, except for recognising more cases of "does not
exist" errors as such.

cmd/flamenco-manager/main.go

@@ -7,6 +7,7 @@ import (
 	"errors"
 	"flag"
 	"fmt"
+	"io/fs"
 	"math/rand"
 	"net"
 	"net/http"
@@ -77,7 +78,7 @@ func main() {
 	// Load configuration.
 	configService := config.NewService()
 	err := configService.Load()
-	if err != nil && !os.IsNotExist(err) {
+	if err != nil && !errors.Is(err, fs.ErrNotExist) {
 		log.Error().Err(err).Msg("loading configuration")
 	}
 

internal/manager/config/config.go

@@ -6,6 +6,7 @@ import (
 	"errors"
 	"fmt"
 	"io"
+	"io/fs"
 	"os"
 	"path"
 	"path/filepath"
@@ -193,7 +194,7 @@ func loadConf(filename string, overrides ...func(c *Conf)) (Conf, error) {
 	yamlFile, err := os.ReadFile(filename)
 	if err != nil {
 		var evt *zerolog.Event
-		if os.IsNotExist(err) {
+		if errors.Is(err, fs.ErrNotExist) {
 			evt = log.Debug()
 		} else {
 			evt = log.Warn().Err(err)

internal/manager/job_compilers/file_loader.go

@@ -4,6 +4,7 @@ package job_compilers
 
 import (
 	"embed"
+	"errors"
 	"fmt"
 	"io"
 	"io/fs"
@@ -64,13 +65,13 @@ func getAvailableFilesystems() []fs.FS {
 func loadFileFromAnyFS(path string) ([]byte, error) {
 	filesystems := getAvailableFilesystems()
 
-	for _, fs := range filesystems {
-		file, err := fs.Open(path)
-		if os.IsNotExist(err) {
+	for _, filesystem := range filesystems {
+		file, err := filesystem.Open(path)
+		if errors.Is(err, fs.ErrNotExist) {
 			continue
 		}
 		if err != nil {
-			return nil, fmt.Errorf("failed to open file %s on filesystem %s: %w", path, fs, err)
+			return nil, fmt.Errorf("failed to open file %s on filesystem %s: %w", path, filesystem, err)
 		}
 		return io.ReadAll(file)
 	}
@@ -137,7 +138,7 @@ func findOnDiskScriptsNextTo(exename string) (string, bool) {
 	logger.Trace().Msg("job compiler: finding on-disk scripts")
 
 	stat, err := os.Stat(scriptsDir)
-	if os.IsNotExist(err) {
+	if errors.Is(err, fs.ErrNotExist) {
 		return scriptsDir, false
 	}
 	if err != nil {

internal/manager/task_logs/log_rotation.go

@@ -3,6 +3,8 @@ package task_logs
 // SPDX-License-Identifier: GPL-3.0-or-later
 
 import (
+	"errors"
+	"io/fs"
 	"os"
 	"path/filepath"
 	"sort"
@@ -44,7 +46,7 @@ func rotateLogFile(logger zerolog.Logger, logpath string) error {
 	// Don't do anything if the file doesn't exist yet.
 	_, err := os.Stat(logpath)
 	if err != nil {
-		if os.IsNotExist(err) {
+		if errors.Is(err, fs.ErrNotExist) {
 			logger.Debug().Msg("log file does not exist, no need to rotate")
 			return nil
 		}

internal/manager/task_logs/log_rotation_test.go

@@ -3,6 +3,8 @@ package task_logs
 // SPDX-License-Identifier: GPL-3.0-or-later
 
 import (
+	"errors"
+	"io/fs"
 	"io/ioutil"
 	"os"
 	"path/filepath"
@@ -112,7 +114,7 @@ func TestMultipleFilesWithHoles(t *testing.T) {
 
 func fileExists(filename string) bool {
 	_, err := os.Stat(filename)
-	return !os.IsNotExist(err)
+	return !errors.Is(err, fs.ErrNotExist)
 }
 
 func fileTouch(filename string) {

internal/manager/task_logs/task_logs_test.go

@@ -3,7 +3,9 @@ package task_logs
 // SPDX-License-Identifier: GPL-3.0-or-later
 
 import (
+	"errors"
 	"fmt"
+	"io/fs"
 	"io/ioutil"
 	"os"
 	"path/filepath"
@@ -78,7 +80,7 @@ func TestLogRotation(t *testing.T) {
 	assert.Equal(t, "Ovo je priča\n", string(contents))
 
 	_, err = os.Stat(filename)
-	assert.True(t, os.IsNotExist(err))
+	assert.True(t, errors.Is(err, fs.ErrNotExist))
 }
 
 func TestLogTail(t *testing.T) {

internal/worker/command_ffmpeg.go

@@ -7,8 +7,10 @@ package worker
 import (
 	"bufio"
 	"context"
+	"errors"
 	"fmt"
 	"io"
+	"io/fs"
 	"os"
 	"os/exec"
 	"path/filepath"
@@ -253,7 +255,7 @@ func createIndexFile(inputGlob string, frameRate float64) ([]string, func(), err
 
 	cleanup := func() {
 		err := os.Remove(indexFilename)
-		if err != nil && !os.IsNotExist(err) {
+		if err != nil && !errors.Is(err, fs.ErrNotExist) {
 			log.Warn().
 				Err(err).
 				Str("filename", indexFilename).

internal/worker/command_file_mgmt.go

@@ -6,7 +6,9 @@ package worker
 
 import (
 	"context"
+	"errors"
 	"fmt"
+	"io/fs"
 	"os"
 	"path/filepath"
 	"regexp"
@@ -99,7 +101,7 @@ func (ce *CommandExecutor) moveAndLog(ctx context.Context, taskID, cmdName, src,
 
 func fileExists(filename string) bool {
 	_, err := os.Stat(filename)
-	return !os.IsNotExist(err)
+	return !errors.Is(err, fs.ErrNotExist)
 }
 
 // timestampedPath returns the path with its modification time appended to the name.

internal/worker/config.go

@@ -71,7 +71,7 @@ func (fcw *FileConfigWrangler) WorkerConfig() (WorkerConfig, error) {
 	err := fcw.loadConfig(configFilename, &wc)
 
 	if err != nil {
-		if !os.IsNotExist(err) {
+		if !errors.Is(err, fs.ErrNotExist) {
 			return wc, err
 		}
 

internal/worker/find_blender/windows.go

@@ -28,7 +28,7 @@ func FindBlender() (string, error) {
 	blenderPath := filepath.Join(dir, "blender.exe")
 	_, err = os.Stat(blenderPath)
 	if err != nil {
-		if os.IsNotExist(err) {
+		if errors.Is(err, fs.ErrNotExist) {
 			return "", fmt.Errorf("blender-launcher found at %s but not its blender.exe", exe)
 		}
 		return "", fmt.Errorf("investigating %s: %w", blenderPath, err)

pkg/shaman/checkout/manager.go

@@ -25,6 +25,7 @@ package checkout
 import (
 	"errors"
 	"fmt"
+	"io/fs"
 	"math/rand"
 	"os"
 	"path/filepath"
@@ -124,7 +125,7 @@ func (m *Manager) PrepareCheckout(checkoutPath string) (ResolvedCheckoutInfo, er
 			Str("checkoutPath", checkoutPath).
 			Logger()
 
-		if stat, err := os.Stat(checkoutPaths.absolutePath); !os.IsNotExist(err) {
+		if stat, err := os.Stat(checkoutPaths.absolutePath); !errors.Is(err, fs.ErrNotExist) {
 			if err == nil {
 				// No error stat'ing this path, indicating it's an existing checkout.
 				lastErr = ErrCheckoutAlreadyExists
@@ -202,7 +203,7 @@ func (m *Manager) SymlinkToCheckout(blobPath, checkoutPath, symlinkRelativePath
 	if err == nil {
 		return err
 	}
-	if !os.IsNotExist(err) {
+	if !errors.Is(err, fs.ErrNotExist) {
 		logger.Error().Err(err).Msg("shaman: unable to create symlink")
 		return err
 	}

pkg/shaman/cleanup.go

@@ -23,6 +23,8 @@
 package shaman
 
 import (
+	"errors"
+	"io/fs"
 	"os"
 	"path/filepath"
 	"time"
@@ -199,7 +201,7 @@ func (s *Server) gcFilterLinkedFiles(checkoutPath string, oldFiles mtimeMap, log
 		}
 		linkTarget, err := filepath.EvalSymlinks(path)
 		if err != nil {
-			if os.IsNotExist(err) {
+			if errors.Is(err, fs.ErrNotExist) {
 				return nil
 			}
 
@@ -229,7 +231,7 @@ func (s *Server) gcDeleteOldFiles(doDryRun bool, oldFiles mtimeMap, logger zerol
 		pathLogger := logger.With().Str("path", path).Logger()
 
 		if stat, err := os.Stat(path); err != nil {
-			if !os.IsNotExist(err) {
+			if !errors.Is(err, fs.ErrNotExist) {
 				pathLogger.Warn().Err(err).Msg("unable to stat to-be-deleted file")
 			}
 		} else if stat.ModTime().After(lastSeenModTime) {

pkg/shaman/cleanup_test.go

@@ -23,6 +23,8 @@
 package shaman
 
 import (
+	"errors"
+	"io/fs"
 	"os"
 	"path/filepath"
 	"testing"
@@ -171,7 +173,7 @@ func TestGCComponents(t *testing.T) {
 	assert.FileExists(t, absPaths["6001.blob"], "file should exist after GC")
 	assert.FileExists(t, absPaths["781.blob"], "file should exist after GC")
 	_, err = os.Stat(absPaths["7488.blob"])
-	assert.True(t, os.IsNotExist(err), "file %s should NOT exist after GC", absPaths["7488.blob"])
+	assert.True(t, errors.Is(err, fs.ErrNotExist), "file %s should NOT exist after GC", absPaths["7488.blob"])
 }
 
 // Test of the high-level GCStorage() function.
@@ -215,9 +217,9 @@ func TestGarbageCollect(t *testing.T) {
 	assert.FileExists(t, absPaths["7488.blob"], "file should exist after dry-run GC")
 	server.GCStorage(false)
 	_, err = os.Stat(absPaths["6001.blob"])
-	assert.True(t, os.IsNotExist(err), "file %s should NOT exist after GC", absPaths["6001.blob"])
+	assert.True(t, errors.Is(err, fs.ErrNotExist), "file %s should NOT exist after GC", absPaths["6001.blob"])
 	_, err = os.Stat(absPaths["7488.blob"])
-	assert.True(t, os.IsNotExist(err), "file %s should NOT exist after GC", absPaths["7488.blob"])
+	assert.True(t, errors.Is(err, fs.ErrNotExist), "file %s should NOT exist after GC", absPaths["7488.blob"])
 
 	// Used files should still exist.
 	assert.FileExists(t, absPaths["781.blob"])

pkg/shaman/filestore/filestore.go

@@ -23,6 +23,8 @@
 package filestore
 
 import (
+	"errors"
+	"io/fs"
 	"os"
 	"path/filepath"
 	"strconv"
@@ -154,7 +156,7 @@ func (s *Store) MoveToStored(checksum string, filesize int64, uploadedFilePath s
 func (s *Store) removeFile(filePath string) error {
 	err := os.Remove(filePath)
 	if err != nil {
-		if !os.IsNotExist(err) {
+		if !errors.Is(err, fs.ErrNotExist) {
 			log.Debug().Err(err).Msg("shaman: unable to delete file; ignoring")
 		}
 	}