modernize: use strings.CutPrefix/SplitSeq/FieldsSeq

Use the CutPrefix(), SplitSeq(), and FieldsSeq() functions from the
strings package when chopping up or iterating over parts of strings, per
golang.org/x/tools/gopls/internal/analysis/modernize/cmd/modernize

Signed-off-by: Nalin Dahyabhai <nalin@redhat.com>

cmd/buildah/containers.go

@@ -277,8 +277,8 @@ func containerOutputHeader(truncate bool) {
 
 func parseCtrFilter(filter string) (*containerFilterParams, error) {
 	params := new(containerFilterParams)
-	filters := strings.Split(filter, ",")
-	for _, param := range filters {
+	filters := strings.SplitSeq(filter, ",")
+	for param := range filters {
 		pair := strings.SplitN(param, "=", 2)
 		if len(pair) != 2 {
 			return nil, fmt.Errorf("incorrect filter value %q, should be of form filter=value", param)

copier/copier.go

@@ -801,7 +801,7 @@ func copierWithSubprocess(bulkReader io.Reader, bulkWriter io.Writer, req reques
 	}
 	loggedOutput := strings.TrimSuffix(errorBuffer.String(), "\n")
 	if len(loggedOutput) > 0 {
-		for _, output := range strings.Split(loggedOutput, "\n") {
+		for output := range strings.SplitSeq(loggedOutput, "\n") {
 			logrus.Debug(output)
 		}
 	}
@@ -1588,8 +1588,8 @@ func mapWithPrefixedKeysWithoutKeyPrefix[K any](m map[string]K, p string) map[st
 	}
 	cloned := make(map[string]K, len(m))
 	for k, v := range m {
-		if strings.HasPrefix(k, p) {
-			cloned[strings.TrimPrefix(k, p)] = v
+		if after, ok := strings.CutPrefix(k, p); ok {
+			cloned[after] = v
 		}
 	}
 	return cloned
@@ -1819,7 +1819,7 @@ func copierHandlerPut(bulkReader io.Reader, req request, idMappings *idtools.IDM
 			return fmt.Errorf("%q is not a subdirectory of %q: %w", directory, req.Root, err)
 		}
 		subdir := ""
-		for _, component := range strings.Split(rel, string(os.PathSeparator)) {
+		for component := range strings.SplitSeq(rel, string(os.PathSeparator)) {
 			subdir = filepath.Join(subdir, component)
 			path := filepath.Join(req.Root, subdir)
 			if err := os.Mkdir(path, 0o700); err == nil {
@@ -2219,7 +2219,7 @@ func copierHandlerMkdir(req request, idMappings *idtools.IDMappings) (*response,
 
 	subdir := ""
 	var created []string
-	for _, component := range strings.Split(rel, string(os.PathSeparator)) {
+	for component := range strings.SplitSeq(rel, string(os.PathSeparator)) {
 		subdir = filepath.Join(subdir, component)
 		path := filepath.Join(req.Root, subdir)
 		if err := os.Mkdir(path, 0o700); err == nil {

copier/xattrs.go

@@ -65,7 +65,7 @@ func Lgetxattrs(path string) (map[string]string, error) {
 		return nil, fmt.Errorf("unable to read list of attributes for %q: size would have been too big", path)
 	}
 	m := make(map[string]string)
-	for _, attribute := range strings.Split(string(list), string('\000')) {
+	for attribute := range strings.SplitSeq(string(list), string('\000')) {
 		if isRelevantXattr(attribute) {
 			attributeSize := initialXattrValueSize
 			var attributeValue []byte

imagebuildah/executor.go

@@ -836,12 +836,12 @@ func (b *Executor) Build(ctx context.Context, stages imagebuilder.Stages) (image
 					}
 				case "ADD", "COPY":
 					for _, flag := range child.Flags { // flags for this instruction
-						if strings.HasPrefix(flag, "--from=") {
+						if after, ok := strings.CutPrefix(flag, "--from="); ok {
 							// TODO: this didn't undergo variable and
 							// arg expansion, so if the previous stage
 							// was named using argument values, we might
 							// not record the right value here.
-							rootfs := strings.TrimPrefix(flag, "--from=")
+							rootfs := after
 							b.rootfsMap[rootfs] = struct{}{}
 							logrus.Debugf("rootfs needed for COPY in stage %d: %q", stageIndex, rootfs)
 							// Populate dependency tree and check
@@ -885,8 +885,8 @@ func (b *Executor) Build(ctx context.Context, stages imagebuilder.Stages) (image
 						// dependency calculation.
 						if strings.HasPrefix(flag, "--mount=") && strings.Contains(flag, "from") {
 							mountFlags := strings.TrimPrefix(flag, "--mount=")
-							fields := strings.Split(mountFlags, ",")
-							for _, field := range fields {
+							fields := strings.SplitSeq(mountFlags, ",")
+							for field := range fields {
 								if mountFrom, hasFrom := strings.CutPrefix(field, "from="); hasFrom {
 									// Check if this base is a stage if yes
 									// add base to current stage's dependency tree

imagebuildah/stage_executor.go

@@ -1913,7 +1913,7 @@ func (s *StageExecutor) getCreatedBy(node *parser.Node, addedContentSummary stri
 
 	switch command {
 	case "ARG":
-		for _, variable := range strings.Fields(node.Original) {
+		for variable := range strings.FieldsSeq(node.Original) {
 			if variable != "ARG" {
 				s.argsFromContainerfile = append(s.argsFromContainerfile, variable)
 			}

info.go

@@ -183,11 +183,11 @@ func getHostDistributionInfo() map[string]string {
 
 	l := bufio.NewScanner(f)
 	for l.Scan() {
-		if strings.HasPrefix(l.Text(), "ID=") {
-			dist["Distribution"] = strings.TrimPrefix(l.Text(), "ID=")
+		if after, ok := strings.CutPrefix(l.Text(), "ID="); ok {
+			dist["Distribution"] = after
 		}
-		if strings.HasPrefix(l.Text(), "VERSION_ID=") {
-			dist["Version"] = strings.Trim(strings.TrimPrefix(l.Text(), "VERSION_ID="), "\"")
+		if after, ok := strings.CutPrefix(l.Text(), "VERSION_ID="); ok {
+			dist["Version"] = strings.Trim(after, "\"")
 		}
 	}
 	return dist

internal/mkcw/archive.go

@@ -543,7 +543,7 @@ func slop(size int64, slop string) int64 {
 	if slop == "" {
 		return size * 5 / 4
 	}
-	for _, factor := range strings.Split(slop, "+") {
+	for factor := range strings.SplitSeq(slop, "+") {
 		factor = strings.TrimSpace(factor)
 		if factor == "" {
 			continue

internal/mkcw/attest.go

@@ -240,8 +240,8 @@ func GenerateMeasurement(workloadConfig WorkloadConfig, firmwareLibrary string)
 			scanner := bufio.NewScanner(&stdout)
 			for scanner.Scan() {
 				line := scanner.Text()
-				if strings.HasPrefix(line, prefix+":") {
-					return strings.TrimSpace(strings.TrimPrefix(line, prefix+":")), nil
+				if after, ok := strings.CutPrefix(line, prefix+":"); ok {
+					return strings.TrimSpace(after), nil
 				}
 			}
 			return "", fmt.Errorf("generating measurement: no line starting with %q found in output from krunfw_measurement", prefix+":")

pkg/cli/build.go

@@ -474,7 +474,7 @@ func readBuildArgFile(buildargfile string, args map[string]string) error {
 	if err != nil {
 		return err
 	}
-	for _, arg := range strings.Split(string(argfile), "\n") {
+	for arg := range strings.SplitSeq(string(argfile), "\n") {
 		if len(arg) == 0 || arg[0] == '#' {
 			continue
 		}

pkg/parse/parse.go

@@ -733,7 +733,7 @@ func GetBuildOutput(buildOutput string) (define.BuildOutputOption, error) {
 	isStdout := false
 	typeSelected := ""
 	pathSelected := ""
-	for _, option := range strings.Split(buildOutput, ",") {
+	for option := range strings.SplitSeq(buildOutput, ",") {
 		key, value, found := strings.Cut(option, "=")
 		if !found {
 			return define.BuildOutputOption{}, fmt.Errorf("invalid build output options %q, expected format key=value", buildOutput)
@@ -789,7 +789,7 @@ func GetConfidentialWorkloadOptions(arg string) (define.ConfidentialWorkloadOpti
 		TempDir: GetTempDir(),
 	}
 	defaults := options
-	for _, option := range strings.Split(arg, ",") {
+	for option := range strings.SplitSeq(arg, ",") {
 		var err error
 		switch {
 		case strings.HasPrefix(option, "type="):
@@ -936,7 +936,7 @@ func GetAutoOptions(base string) (*storageTypes.AutoUserNsOptions, error) {
 	if len(parts) == 1 {
 		return &options, nil
 	}
-	for _, o := range strings.Split(parts[1], ",") {
+	for o := range strings.SplitSeq(parts[1], ",") {
 		v := strings.SplitN(o, "=", 2)
 		if len(v) != 2 {
 			return nil, fmt.Errorf("invalid option specified: %q", o)

tests/conformance/conformance_test.go

@@ -672,10 +672,10 @@ func buildUsingDocker(ctx context.Context, t *testing.T, client *docker.Client,
 	// read the Dockerfile so that we can pull base images
 	dockerfileContent, err := os.ReadFile(dockerfileName)
 	require.NoErrorf(t, err, "reading dockerfile %q", dockerfileName)
-	for _, line := range strings.Split(string(dockerfileContent), "\n") {
+	for line := range strings.SplitSeq(string(dockerfileContent), "\n") {
 		line = strings.TrimSpace(line)
-		if strings.HasPrefix(line, "# syntax=") {
-			pullImageIfMissing(t, client, strings.TrimPrefix(line, "# syntax="))
+		if after, ok := strings.CutPrefix(line, "# syntax="); ok {
+			pullImageIfMissing(t, client, after)
 		}
 	}
 	parsed, err := imagebuilder.ParseDockerfile(bytes.NewReader(dockerfileContent))
@@ -1131,8 +1131,8 @@ func applyLayerToFSTree(t *testing.T, layer *Layer, root *FSEntry) {
 		}
 		// if the item is a whiteout, strip the "this is a whiteout
 		// entry" prefix and remove the item it names
-		if strings.HasPrefix(base, ".wh.") {
-			delete(dirEntry.Children, strings.TrimPrefix(base, ".wh."))
+		if after, ok := strings.CutPrefix(base, ".wh."); ok {
+			delete(dirEntry.Children, after)
 			continue
 		}
 		// if the item already exists, make sure we don't get confused
@@ -1281,8 +1281,8 @@ func compareJSON(a, b map[string]any, skip []string) (missKeys, leftKeys, diffKe
 			var nextSkip []string
 			prefix := k + ":"
 			for _, s := range skip {
-				if strings.HasPrefix(s, prefix) {
-					nextSkip = append(nextSkip, strings.TrimPrefix(s, prefix))
+				if after, ok0 := strings.CutPrefix(s, prefix); ok0 {
+					nextSkip = append(nextSkip, after)
 				}
 			}
 			submiss, subleft, subdiff, ok := compareJSON(v.(map[string]any), vb.(map[string]any), nextSkip)