CAS diff command (#849)

Utility to help diff changes between 2 manifests in CAS directories.

Author: unmultimedio

cmd/casdiff/casdiff.go

@@ -0,0 +1,227 @@
+// Copyright 2021-2025 Buf Technologies, Inc.
+//
+// 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 (
+	"context"
+	"errors"
+	"fmt"
+	"io/fs"
+	"strconv"
+
+	"github.com/bufbuild/buf/private/bufpkg/bufcas"
+	"github.com/bufbuild/buf/private/pkg/app/appcmd"
+	"github.com/bufbuild/buf/private/pkg/app/appext"
+	"github.com/bufbuild/buf/private/pkg/slicesext"
+	"github.com/bufbuild/buf/private/pkg/slogapp"
+	"github.com/bufbuild/buf/private/pkg/storage"
+	"github.com/bufbuild/buf/private/pkg/storage/storageos"
+	"github.com/bufbuild/modules/private/bufpkg/bufstate"
+	"github.com/spf13/pflag"
+)
+
+// format is a format to print the casdiff.
+type format int
+
+const (
+	formatFlagName      = "format"
+	formatFlagShortName = "f"
+)
+
+const (
+	formatText format = iota + 1
+	formatMarkdown
+)
+
+//nolint:gochecknoglobals // treated as consts
+var (
+	formatsValuesToNames = map[format]string{
+		formatText:     "text",
+		formatMarkdown: "markdown",
+	}
+	formatsNamesToValues, _ = slicesext.ToUniqueValuesMap(
+		slicesext.MapKeysToSlice(formatsValuesToNames),
+		func(f format) string { return formatsValuesToNames[f] },
+	)
+	allFormatsString = slicesext.MapKeysToSortedSlice(formatsNamesToValues)
+)
+
+func (f format) String() string {
+	if n, ok := formatsValuesToNames[f]; ok {
+		return n
+	}
+	return strconv.Itoa(int(f))
+}
+
+func newCommand(name string) *appcmd.Command {
+	builder := appext.NewBuilder(
+		name,
+		appext.BuilderWithLoggerProvider(slogapp.LoggerProvider),
+	)
+	flags := newFlags()
+	return &appcmd.Command{
+		Use:       name + " <from> <to>",
+		Short:     "Run a CAS diff.",
+		Args:      appcmd.ExactArgs(2),
+		BindFlags: flags.bind,
+		Run: builder.NewRunFunc(
+			func(ctx context.Context, container appext.Container) error {
+				return run(ctx, container, flags)
+			},
+		),
+	}
+}
+
+type flags struct {
+	format string
+}
+
+func newFlags() *flags {
+	return &flags{}
+}
+
+func (f *flags) bind(flagSet *pflag.FlagSet) {
+	flagSet.StringVarP(
+		&f.format,
+		formatFlagName,
+		formatFlagShortName,
+		formatText.String(),
+		fmt.Sprintf(`The out format to use. Must be one of %s`, allFormatsString),
+	)
+}
+
+func run(
+	ctx context.Context,
+	container appext.Container,
+	flags *flags,
+) error {
+	format, ok := formatsNamesToValues[flags.format]
+	if !ok {
+		return fmt.Errorf("unsupported format %s", flags.format)
+	}
+	from, to := container.Arg(0), container.Arg(1) //nolint:varnamelen // from/to used symmetrically
+	if from == to {
+		return printDiff(newManifestDiff(), format)
+	}
+	// first, attempt to match from/to as module references in a state file in the same directory
+	// where the command is run
+	bucket, err := storageos.NewProvider().NewReadWriteBucket(".")
+	if err != nil {
+		return fmt.Errorf("new rw bucket: %w", err)
+	}
+	moduleStateReader, err := bucket.Get(ctx, bufstate.ModStateFileName)
+	if err != nil {
+		if !errors.Is(err, fs.ErrNotExist) {
+			return fmt.Errorf("read module state file: %w", err)
+		}
+		// if the state file does not exist, we assume we are in the cas directory, and that from/to are
+		// the manifest paths
+		mdiff, err := calculateDiffFromCASDirectory(ctx, bucket, from, to)
+		if err != nil {
+			return fmt.Errorf("calculate cas diff: %w", err)
+		}
+		return printDiff(mdiff, format)
+	}
+	// state file was found, attempt to parse it and match from/to with its references
+	stateRW, err := bufstate.NewReadWriter()
+	if err != nil {
+		return fmt.Errorf("new state rw: %w", err)
+	}
+	moduleState, err := stateRW.ReadModStateFile(moduleStateReader)
+	if err != nil {
+		return fmt.Errorf("read module state: %w", err)
+	}
+	var (
+		fromManifestPath string
+		toManifestPath   string
+	)
+	for _, ref := range moduleState.GetReferences() {
+		if ref.GetName() == from {
+			fromManifestPath = ref.GetDigest()
+			if toManifestPath != "" {
+				break
+			}
+		} else if ref.GetName() == to {
+			toManifestPath = ref.GetDigest()
+			if fromManifestPath != "" {
+				break
+			}
+		}
+	}
+	if fromManifestPath == "" {
+		return fmt.Errorf("from reference %s not found in the module state file", from)
+	}
+	if toManifestPath == "" {
+		return fmt.Errorf("to reference %s not found in the module state file", to)
+	}
+	if fromManifestPath == toManifestPath {
+		return printDiff(newManifestDiff(), format)
+	}
+	casBucket, err := storageos.NewProvider().NewReadWriteBucket("cas")
+	if err != nil {
+		return fmt.Errorf("new rw cas bucket: %w", err)
+	}
+	mdiff, err := calculateDiffFromCASDirectory(ctx, casBucket, fromManifestPath, toManifestPath)
+	if err != nil {
+		return fmt.Errorf("calculate cas diff from state references: %w", err)
+	}
+	return printDiff(mdiff, format)
+}
+
+// calculateDiffFromCASDirectory takes the cas bucket, and the from/to manifest paths to calculate a
+// diff.
+func calculateDiffFromCASDirectory(
+	ctx context.Context,
+	casBucket storage.ReadBucket,
+	fromManifestPath string,
+	toManifestPath string,
+) (*manifestDiff, error) {
+	if fromManifestPath == toManifestPath {
+		return newManifestDiff(), nil
+	}
+	fromManifest, err := readManifest(ctx, casBucket, fromManifestPath)
+	if err != nil {
+		return nil, fmt.Errorf("read manifest from: %w", err)
+	}
+	toManifest, err := readManifest(ctx, casBucket, toManifestPath)
+	if err != nil {
+		return nil, fmt.Errorf("read manifest to: %w", err)
+	}
+	return buildManifestDiff(ctx, fromManifest, toManifest, casBucket)
+}
+
+func readManifest(ctx context.Context, bucket storage.ReadBucket, manifestPath string) (bufcas.Manifest, error) {
+	data, err := storage.ReadPath(ctx, bucket, manifestPath)
+	if err != nil {
+		return nil, fmt.Errorf("read path: %w", err)
+	}
+	m, err := bufcas.ParseManifest(string(data))
+	if err != nil {
+		return nil, fmt.Errorf("parse manifest: %w", err)
+	}
+	return m, nil
+}
+
+func printDiff(mdiff *manifestDiff, format format) error {
+	switch format {
+	case formatText:
+		mdiff.printText()
+	case formatMarkdown:
+		mdiff.printMarkdown()
+	default:
+		return fmt.Errorf("format %s not supported", format.String())
+	}
+	return nil
+}

cmd/casdiff/main.go

@@ -0,0 +1,29 @@
+// Copyright 2021-2025 Buf Technologies, Inc.
+//
+// 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 (
+	"context"
+
+	"github.com/bufbuild/buf/private/pkg/app/appcmd"
+)
+
+const (
+	rootCmdName = "casdiff"
+)
+
+func main() {
+	appcmd.Main(context.Background(), newCommand(rootCmdName))
+}