Never regenerate mf.pb.go during checks; fail when it is stale (closes #71)

The test and format scripts regenerated mfer/mf.pb.go whenever
mfer/mf.proto looked newer by mtime, which a fresh checkout often causes,
so make check could rewrite a committed file and needed protoc. Nothing
regenerates it any more except make generate (script/generate), which
refuses to run unless protoc 33.4 and protoc-gen-go v1.36.11, the
versions that wrote the committed file, are on PATH, and records the
hash of mf.proto in mfer/mf.proto.sha256. A Go test compares that hash
with mf.proto and fails, naming make generate, when they differ. The
mtime rule, the unused protoc-gen-go v1.28.1 install rule, make clean's
deletion of mf.pb.go and the Dockerfile's touch workarounds are removed.

Model: opus-5-5

Dockerfile

@@ -8,9 +8,6 @@ RUN go mod download
 
 COPY . .
 
-# Touch .pb.go so make does not try to regenerate via protoc (file is committed)
-RUN touch mfer/mf.pb.go
-
 # Go half of fmt-check only: this image has no node, so no prettier. The
 # markdown half runs in the mdfmt stage below.
 RUN make fmt-check-go
@@ -46,9 +43,6 @@ RUN go mod download
 
 COPY . .
 
-# Touch .pb.go so make does not try to regenerate via protoc (file is committed)
-RUN touch mfer/mf.pb.go
-
 RUN make test
 
 # A build context sent as a tar archive, as upaas sends it, keeps its files'

Makefile

@@ -2,7 +2,6 @@ export DOCKER_BUILDKIT := 1
 export PROGRESS_NO_TRUNC := 1
 GOPATH := $(shell go env GOPATH)
 export PATH := $(PATH):$(GOPATH)/bin
-PROTOC_GEN_GO := $(GOPATH)/bin/protoc-gen-go
 SOURCEFILES := mfer/*.go mfer/*.proto internal/*/*.go cmd/*/*.go go.mod go.sum
 ARCH := $(shell uname -m)
 GITREV_BUILD := $(shell bash $(PWD)/bin/gitrev.sh 2>/dev/null || echo unknown)
@@ -13,7 +12,7 @@ GOLDFLAGS += -X main.Version=$(VERSION)
 GOLDFLAGS += -X main.Gitrev=$(GITREV_BUILD)
 GOFLAGS := -ldflags "$(GOLDFLAGS)"
 
-.PHONY: bootstrap setup docker default run ci test fuzz check lint fmt fmt-check fmt-check-go fmt-check-md hooks fixme
+.PHONY: bootstrap setup docker default run ci test fuzz check lint fmt fmt-check fmt-check-go fmt-check-md hooks fixme generate
 
 default: fmt test
 
@@ -35,9 +34,6 @@ test:
 fuzz:
 	@script/fuzz
 
-$(PROTOC_GEN_GO):
-	test -e $(PROTOC_GEN_GO) || go install -v google.golang.org/protobuf/cmd/protoc-gen-go@v1.28.1
-
 fixme:
 	@grep -nir fixme . | grep -v Makefile
 
@@ -58,15 +54,14 @@ fmt-check-md:
 hooks:
 	@script/install-precommit
 
-mfer/mf.pb.go: mfer/mf.proto
-	cd mfer && go generate .
+generate:
+	@script/generate
 
-bin/mfer: $(SOURCEFILES) mfer/mf.pb.go
-	protoc --version
+bin/mfer: $(SOURCEFILES)
 	cd cmd/mfer && go build -tags urfave_cli_no_docs -o ../../bin/mfer $(GOFLAGS) .
 
 clean:
-	rm -rfv mfer/*.pb.go bin/mfer cmd/mfer/mfer *.dockerimage
+	rm -rfv bin/mfer cmd/mfer/mfer *.dockerimage
 
 fmt:
 	@script/fmt

README.md

@@ -72,8 +72,19 @@ provide:
   `script/bootstrap`, then `script/install-precommit`
 - `script/projectname` — output the project name (`mfer`); used by other scripts
   such as `script/docker`
-- `script/test` — run the test suite (`go test`), regenerating the protobuf code
-  first if it is stale
+- `script/test` — run the test suite (`go test`); one test fails when
+  `mfer/mf.proto` no longer matches the hash `script/generate` recorded
+- `script/generate` (`make generate`) — regenerate `mfer/mf.pb.go` from
+  `mfer/mf.proto` and record the hash of that `mfer/mf.proto` in
+  `mfer/mf.proto.sha256`; the only thing that regenerates the committed
+  `mfer/mf.pb.go`. It needs the exact versions that wrote the committed file,
+  and refuses to run with any other: `protoc` 33.4 (unpack
+  `protoc-33.4-<platform>.zip` from
+  [its release](https://github.com/protocolbuffers/protobuf/releases/tag/v33.4)
+  and put its `bin/protoc` on `PATH`) and `protoc-gen-go` v1.36.11
+  (`go install google.golang.org/protobuf/cmd/protoc-gen-go@v1.36.11`, which
+  installs it in `$(go env GOPATH)/bin`; `make generate` adds that directory to
+  `PATH`)
 - `script/fuzz` — fuzz the manifest parser for one minute; run by hand
   (`make fuzz`), never by CI, while `script/test` runs its committed seed corpus
   as ordinary tests

internal/cli/check.go

@@ -298,7 +298,11 @@ func (mfa *CLIApp) checkManifestOperation(ctx *cli.Context) error {
 	log.Infof("checking manifest %s with base %s", manifestPath, basePath)
 
 	// Create checker
-	chk, err := mfer.NewChecker(manifestPath, basePath, mfa.Fs)
+	chk, err := mfer.NewChecker(&mfer.CheckerOptions{
+		ManifestPath: manifestPath,
+		BasePath:     basePath,
+		Fs:           mfa.Fs,
+	})
 	if err != nil {
 		return fmt.Errorf("failed to load manifest: %w", err)
 	}

internal/cli/entry_test.go

@@ -504,7 +504,10 @@ func TestGenerateExcludesDotfilesByDefault(t *testing.T) {
 	assert.True(t, exists)
 
 	// Verify manifest only has 1 file (the non-dotfile)
-	manifest, err := mfer.NewManifestFromFile(fs, testMF)
+	manifest, err := mfer.NewManifestFromFile(&mfer.ManifestFromFileOptions{
+		Path: testMF,
+		Fs:   fs,
+	})
 	require.NoError(t, err)
 	assert.Len(t, manifest.Files(), 1)
 	assert.Equal(t, "file1.txt", manifest.Files()[0].GetPath())
@@ -528,7 +531,10 @@ func TestGenerateWithIncludeDotfiles(t *testing.T) {
 	require.Equal(t, 0, exitCode)
 
 	// Verify manifest has 2 files (including dotfile)
-	manifest, err := mfer.NewManifestFromFile(fs, testMF)
+	manifest, err := mfer.NewManifestFromFile(&mfer.ManifestFromFileOptions{
+		Path: testMF,
+		Fs:   fs,
+	})
 	require.NoError(t, err)
 	assert.Len(t, manifest.Files(), 2)
 }

internal/cli/errmsg_test.go

@@ -61,7 +61,11 @@ func unsignedChecker(t *testing.T) *mfer.Checker {
 	require.NoError(t, s.ToManifest(context.Background(), &buf, nil))
 	require.NoError(t, afero.WriteFile(fs, "/d/index.mf", buf.Bytes(), 0o644))
 
-	chk, err := mfer.NewChecker("/d/index.mf", "/d", fs)
+	chk, err := mfer.NewChecker(&mfer.CheckerOptions{
+		ManifestPath: "/d/index.mf",
+		BasePath:     "/d",
+		Fs:           fs,
+	})
 	require.NoError(t, err)
 	require.False(t, chk.IsSigned())
 
@@ -167,7 +171,11 @@ func signedChecker(t *testing.T) *mfer.Checker {
 	fs := afero.NewMemMapFs()
 	require.NoError(t, afero.WriteFile(fs, "/index.mf", buf.Bytes(), 0o644))
 
-	chk, err := mfer.NewChecker("/index.mf", "/", fs)
+	chk, err := mfer.NewChecker(&mfer.CheckerOptions{
+		ManifestPath: "/index.mf",
+		BasePath:     "/",
+		Fs:           fs,
+	})
 	require.NoError(t, err)
 	require.True(t, chk.IsSigned())
 

internal/cli/freshen.go

@@ -445,7 +445,10 @@ func (mfa *CLIApp) loadExistingEntries(
 	log.Infof("loading manifest from %s", manifestPath)
 
 	// Load existing manifest
-	manifest, err := mfer.NewManifestFromFile(mfa.Fs, manifestPath)
+	manifest, err := mfer.NewManifestFromFile(&mfer.ManifestFromFileOptions{
+		Path: manifestPath,
+		Fs:   mfa.Fs,
+	})
 	if err != nil {
 		return nil, fmt.Errorf("failed to load manifest: %w", err)
 	}

internal/cli/freshen_test.go

@@ -58,7 +58,10 @@ func TestFreshenUnchanged(t *testing.T) {
 	setupFreshenDir(t, fs)
 
 	// Parse manifest to verify
-	manifest, err := mfer.NewManifestFromFile(fs, "/testdir/.index.mf")
+	manifest, err := mfer.NewManifestFromFile(&mfer.ManifestFromFileOptions{
+		Path: "/testdir/.index.mf",
+		Fs:   fs,
+	})
 	require.NoError(t, err)
 	assert.Len(t, manifest.Files(), 2)
 }
@@ -70,7 +73,10 @@ func TestFreshenWithChanges(t *testing.T) {
 	setupFreshenDir(t, fs)
 
 	// Verify initial manifest has 2 files
-	manifest, err := mfer.NewManifestFromFile(fs, "/testdir/.index.mf")
+	manifest, err := mfer.NewManifestFromFile(&mfer.ManifestFromFileOptions{
+		Path: "/testdir/.index.mf",
+		Fs:   fs,
+	})
 	require.NoError(t, err)
 	assert.Len(t, manifest.Files(), 2)
 

mfer/builder_test.go

@@ -5,10 +5,12 @@ import (
 	"bytes"
 	"context"
 	"fmt"
+	"path/filepath"
 	"strings"
 	"testing"
 	"time"
 
+	"github.com/spf13/afero"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 )
@@ -397,6 +399,29 @@ func TestNewManifestFromReaderTruncated(t *testing.T) {
 	assert.Error(t, err)
 }
 
+func TestNewManifestFromFileRequiresPath(t *testing.T) {
+	t.Parallel()
+
+	_, err := NewManifestFromFile(nil)
+	require.ErrorIs(t, err, errManifestPathEmpty)
+
+	_, err = NewManifestFromFile(&ManifestFromFileOptions{Fs: afero.NewMemMapFs()})
+	require.ErrorIs(t, err, errManifestPathEmpty)
+}
+
+func TestNewManifestFromFileNilFsUsesOsFs(t *testing.T) {
+	t.Parallel()
+
+	path := filepath.Join(t.TempDir(), "index.mf")
+	createTestManifest(t, afero.NewOsFs(), path, map[string][]byte{
+		testFileName: []byte("hello"),
+	})
+
+	m, err := NewManifestFromFile(&ManifestFromFileOptions{Path: path})
+	require.NoError(t, err)
+	assert.Len(t, m.Files(), 1)
+}
+
 func TestManifestString(t *testing.T) {
 	t.Parallel()
 

mfer/checker.go

@@ -14,7 +14,11 @@ import (
 	"github.com/spf13/afero"
 )
 
-var errNoSigningPubKey = errors.New("manifest has no signing public key")
+var (
+	errNoSigningPubKey   = errors.New("manifest has no signing public key")
+	errManifestPathEmpty = errors.New("manifest path cannot be empty")
+	errBasePathEmpty     = errors.New("base path cannot be empty")
+)
 
 // Result represents the outcome of checking a single file.
 type Result struct {
@@ -82,20 +86,42 @@ type Checker struct {
 	signingPubKey []byte
 }
 
-// NewChecker creates a new Checker for the given manifest, base path, and filesystem.
-// The basePath is the directory relative to which manifest paths are resolved.
-// If fs is nil, the real filesystem (OsFs) is used.
-func NewChecker(manifestPath string, basePath string, fs afero.Fs) (*Checker, error) {
+// CheckerOptions configures a Checker.
+type CheckerOptions struct {
+	// ManifestPath is the manifest file to check against (required).
+	ManifestPath string
+	// BasePath is the directory relative to which manifest paths are
+	// resolved (required).
+	BasePath string
+	// Fs is the filesystem to use, defaults to OsFs if nil.
+	Fs afero.Fs
+}
+
+// NewChecker creates a new Checker with the given options. It returns an
+// error if opts is nil or either path is empty.
+func NewChecker(opts *CheckerOptions) (*Checker, error) {
+	if opts == nil || opts.ManifestPath == "" {
+		return nil, errManifestPathEmpty
+	}
+
+	if opts.BasePath == "" {
+		return nil, errBasePathEmpty
+	}
+
+	fs := opts.Fs
 	if fs == nil {
 		fs = afero.NewOsFs()
 	}
 
-	m, err := NewManifestFromFile(fs, manifestPath)
+	m, err := NewManifestFromFile(&ManifestFromFileOptions{
+		Path: opts.ManifestPath,
+		Fs:   fs,
+	})
 	if err != nil {
 		return nil, err
 	}
 
-	abs, err := filepath.Abs(basePath)
+	abs, err := filepath.Abs(opts.BasePath)
 	if err != nil {
 		return nil, err
 	}
@@ -108,7 +134,7 @@ func NewChecker(manifestPath string, basePath string, fs afero.Fs) (*Checker, er
 	}
 
 	// Compute manifest's relative path from basePath for exclusion in FindExtraFiles
-	absManifest, err := filepath.Abs(manifestPath)
+	absManifest, err := filepath.Abs(opts.ManifestPath)
 	if err != nil {
 		return nil, err
 	}

mfer/checker_test.go

@@ -5,6 +5,8 @@ import (
 	"bytes"
 	"context"
 	"fmt"
+	"os"
+	"path/filepath"
 	"testing"
 	"time"
 
@@ -14,9 +16,11 @@ import (
 )
 
 const (
-	testFile1      = "file1.txt"
-	testFile2      = "file2.txt"
-	testExistsFile = "exists.txt"
+	testFile1        = "file1.txt"
+	testFile2        = "file2.txt"
+	testExistsFile   = "exists.txt"
+	testManifestPath = "/manifest.mf"
+	testDataDir      = "/data"
 )
 
 func TestStatusString(t *testing.T) {
@@ -66,15 +70,13 @@ func createTestManifest(
 }
 
 // createFilesOnDisk creates the given files on the filesystem under
-// /data.
+// testDataDir.
 func createFilesOnDisk(t *testing.T, fs afero.Fs, files map[string][]byte) {
 	t.Helper()
 
-	basePath := "/data"
-
 	for path, content := range files {
-		fullPath := basePath + "/" + path
-		require.NoError(t, fs.MkdirAll(basePath, 0o755))
+		fullPath := testDataDir + "/" + path
+		require.NoError(t, fs.MkdirAll(testDataDir, 0o755))
 		require.NoError(t, afero.WriteFile(fs, fullPath, content, 0o644))
 	}
 }
@@ -90,9 +92,13 @@ func TestNewChecker(t *testing.T) {
 			testFile1: []byte("hello"),
 			testFile2: []byte("world"),
 		}
-		createTestManifest(t, fs, "/manifest.mf", files)
+		createTestManifest(t, fs, testManifestPath, files)
 
-		chk, err := NewChecker("/manifest.mf", "/", fs)
+		chk, err := NewChecker(&CheckerOptions{
+			ManifestPath: testManifestPath,
+			BasePath:     "/",
+			Fs:           fs,
+		})
 		require.NoError(t, err)
 		assert.NotNil(t, chk)
 		assert.Equal(t, FileCount(2), chk.FileCount())
@@ -102,7 +108,11 @@ func TestNewChecker(t *testing.T) {
 		t.Parallel()
 
 		fs := afero.NewMemMapFs()
-		_, err := NewChecker("/nonexistent.mf", "/", fs)
+		_, err := NewChecker(&CheckerOptions{
+			ManifestPath: "/nonexistent.mf",
+			BasePath:     "/",
+			Fs:           fs,
+		})
 		assert.Error(t, err)
 	})
 
@@ -111,11 +121,73 @@ func TestNewChecker(t *testing.T) {
 
 		fs := afero.NewMemMapFs()
 		require.NoError(t, afero.WriteFile(fs, "/bad.mf", []byte("not a manifest"), 0o644))
-		_, err := NewChecker("/bad.mf", "/", fs)
+		_, err := NewChecker(&CheckerOptions{
+			ManifestPath: "/bad.mf",
+			BasePath:     "/",
+			Fs:           fs,
+		})
 		assert.Error(t, err)
 	})
 }
 
+func TestNewCheckerRequiredPaths(t *testing.T) {
+	t.Parallel()
+
+	for _, tc := range []struct {
+		name string
+		opts *CheckerOptions
+		want string
+		is   error
+	}{
+		{
+			name: "nil options",
+			opts: nil,
+			want: "manifest path cannot be empty",
+			is:   errManifestPathEmpty,
+		},
+		{
+			name: "empty manifest path",
+			opts: &CheckerOptions{BasePath: testDataDir},
+			want: "manifest path cannot be empty",
+			is:   errManifestPathEmpty,
+		},
+		{
+			name: "empty base path",
+			opts: &CheckerOptions{ManifestPath: testManifestPath},
+			want: "base path cannot be empty",
+			is:   errBasePathEmpty,
+		},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			t.Parallel()
+
+			chk, err := NewChecker(tc.opts)
+			require.ErrorIs(t, err, tc.is)
+			require.EqualError(t, err, tc.want)
+			assert.Nil(t, chk)
+		})
+	}
+}
+
+func TestNewCheckerNilFsUsesOsFs(t *testing.T) {
+	t.Parallel()
+
+	dir := t.TempDir()
+	manifestPath := filepath.Join(dir, "index.mf")
+	content := []byte("hello")
+	createTestManifest(t, afero.NewOsFs(), manifestPath, map[string][]byte{
+		testFile1: content,
+	})
+	require.NoError(t, os.WriteFile(filepath.Join(dir, testFile1), content, 0o600))
+
+	chk, err := NewChecker(&CheckerOptions{ManifestPath: manifestPath, BasePath: dir})
+	require.NoError(t, err)
+
+	results := make(chan Result, 1)
+	require.NoError(t, chk.Check(context.Background(), results, nil))
+	assert.Equal(t, StatusOK, (<-results).Status)
+}
+
 func TestCheckerFileCountAndTotalBytes(t *testing.T) {
 	t.Parallel()
 
@@ -125,9 +197,13 @@ func TestCheckerFileCountAndTotalBytes(t *testing.T) {
 		"medium.txt": []byte("hello world"),
 		"large.txt":  bytes.Repeat([]byte("x"), 1000),
 	}
-	createTestManifest(t, fs, "/manifest.mf", files)
+	createTestManifest(t, fs, testManifestPath, files)
 
-	chk, err := NewChecker("/manifest.mf", "/", fs)
+	chk, err := NewChecker(&CheckerOptions{
+		ManifestPath: testManifestPath,
+		BasePath:     "/",
+		Fs:           fs,
+	})
 	require.NoError(t, err)
 
 	assert.Equal(t, FileCount(3), chk.FileCount())
@@ -142,10 +218,14 @@ func TestCheckAllFilesOK(t *testing.T) {
 		testFile1: []byte("content one"),
 		testFile2: []byte("content two"),
 	}
-	createTestManifest(t, fs, "/manifest.mf", files)
+	createTestManifest(t, fs, testManifestPath, files)
 	createFilesOnDisk(t, fs, files)
 
-	chk, err := NewChecker("/manifest.mf", "/data", fs)
+	chk, err := NewChecker(&CheckerOptions{
+		ManifestPath: testManifestPath,
+		BasePath:     testDataDir,
+		Fs:           fs,
+	})
 	require.NoError(t, err)
 
 	results := make(chan Result, 10)
@@ -172,13 +252,17 @@ func TestCheckMissingFile(t *testing.T) {
 		testExistsFile: []byte("I exist"),
 		"missing.txt":  []byte("I don't exist on disk"),
 	}
-	createTestManifest(t, fs, "/manifest.mf", files)
+	createTestManifest(t, fs, testManifestPath, files)
 	// Only create one file
 	createFilesOnDisk(t, fs, map[string][]byte{
 		testExistsFile: []byte("I exist"),
 	})
 
-	chk, err := NewChecker("/manifest.mf", "/data", fs)
+	chk, err := NewChecker(&CheckerOptions{
+		ManifestPath: testManifestPath,
+		BasePath:     testDataDir,
+		Fs:           fs,
+	})
 	require.NoError(t, err)
 
 	results := make(chan Result, 10)
@@ -211,13 +295,17 @@ func TestCheckSizeMismatch(t *testing.T) {
 	files := map[string][]byte{
 		testFileName: []byte("original content"),
 	}
-	createTestManifest(t, fs, "/manifest.mf", files)
+	createTestManifest(t, fs, testManifestPath, files)
 	// Create file with different size
 	createFilesOnDisk(t, fs, map[string][]byte{
 		testFileName: []byte("short"),
 	})
 
-	chk, err := NewChecker("/manifest.mf", "/data", fs)
+	chk, err := NewChecker(&CheckerOptions{
+		ManifestPath: testManifestPath,
+		BasePath:     testDataDir,
+		Fs:           fs,
+	})
 	require.NoError(t, err)
 
 	results := make(chan Result, 10)
@@ -237,7 +325,7 @@ func TestCheckHashMismatch(t *testing.T) {
 	files := map[string][]byte{
 		testFileName: originalContent,
 	}
-	createTestManifest(t, fs, "/manifest.mf", files)
+	createTestManifest(t, fs, testManifestPath, files)
 	// Create file with same size but different content
 	differentContent := []byte("different contnt") // same length (16 bytes) but different
 	require.Len(t, differentContent, len(originalContent), "test requires same length")
@@ -245,7 +333,11 @@ func TestCheckHashMismatch(t *testing.T) {
 		testFileName: differentContent,
 	})
 
-	chk, err := NewChecker("/manifest.mf", "/data", fs)
+	chk, err := NewChecker(&CheckerOptions{
+		ManifestPath: testManifestPath,
+		BasePath:     testDataDir,
+		Fs:           fs,
+	})
 	require.NoError(t, err)
 
 	results := make(chan Result, 10)
@@ -265,10 +357,14 @@ func TestCheckWithProgress(t *testing.T) {
 		testFile1: bytes.Repeat([]byte("a"), 100),
 		testFile2: bytes.Repeat([]byte("b"), 200),
 	}
-	createTestManifest(t, fs, "/manifest.mf", files)
+	createTestManifest(t, fs, testManifestPath, files)
 	createFilesOnDisk(t, fs, files)
 
-	chk, err := NewChecker("/manifest.mf", "/data", fs)
+	chk, err := NewChecker(&CheckerOptions{
+		ManifestPath: testManifestPath,
+		BasePath:     testDataDir,
+		Fs:           fs,
+	})
 	require.NoError(t, err)
 
 	results := make(chan Result, 10)
@@ -305,10 +401,14 @@ func TestCheckContextCancellation(t *testing.T) {
 		files[string(rune('a'+i%26))+".txt"] = bytes.Repeat([]byte("x"), 1000)
 	}
 
-	createTestManifest(t, fs, "/manifest.mf", files)
+	createTestManifest(t, fs, testManifestPath, files)
 	createFilesOnDisk(t, fs, files)
 
-	chk, err := NewChecker("/manifest.mf", "/data", fs)
+	chk, err := NewChecker(&CheckerOptions{
+		ManifestPath: testManifestPath,
+		BasePath:     testDataDir,
+		Fs:           fs,
+	})
 	require.NoError(t, err)
 
 	ctx, cancel := context.WithCancel(context.Background())
@@ -327,7 +427,7 @@ func TestFindExtraFiles(t *testing.T) {
 	manifestFiles := map[string][]byte{
 		testFile1: []byte("in manifest"),
 	}
-	createTestManifest(t, fs, "/manifest.mf", manifestFiles)
+	createTestManifest(t, fs, testManifestPath, manifestFiles)
 
 	// Disk has file1 and file2
 	createFilesOnDisk(t, fs, map[string][]byte{
@@ -335,7 +435,11 @@ func TestFindExtraFiles(t *testing.T) {
 		testFile2: []byte("extra file"),
 	})
 
-	chk, err := NewChecker("/manifest.mf", "/data", fs)
+	chk, err := NewChecker(&CheckerOptions{
+		ManifestPath: testManifestPath,
+		BasePath:     testDataDir,
+		Fs:           fs,
+	})
 	require.NoError(t, err)
 
 	results := make(chan Result, 10)
@@ -368,10 +472,14 @@ func TestFindExtraFilesSkipsManifestAndDotfiles(t *testing.T) {
 	require.NoError(t, afero.WriteFile(fs, "/data/.hidden", []byte("hidden"), 0o644))
 	require.NoError(t, afero.WriteFile(fs, "/data/.config/settings", []byte("cfg"), 0o644))
 	// Create a real extra file
-	require.NoError(t, fs.MkdirAll("/data", 0o755))
+	require.NoError(t, fs.MkdirAll(testDataDir, 0o755))
 	require.NoError(t, afero.WriteFile(fs, "/data/extra.txt", []byte("extra"), 0o644))
 
-	chk, err := NewChecker("/data/.index.mf", "/data", fs)
+	chk, err := NewChecker(&CheckerOptions{
+		ManifestPath: "/data/.index.mf",
+		BasePath:     testDataDir,
+		Fs:           fs,
+	})
 	require.NoError(t, err)
 
 	results := make(chan Result, 10)
@@ -400,10 +508,14 @@ func TestFindExtraFilesContextCancellation(t *testing.T) {
 
 	fs := afero.NewMemMapFs()
 	files := map[string][]byte{testFileName: []byte("data")}
-	createTestManifest(t, fs, "/manifest.mf", files)
+	createTestManifest(t, fs, testManifestPath, files)
 	createFilesOnDisk(t, fs, files)
 
-	chk, err := NewChecker("/manifest.mf", "/data", fs)
+	chk, err := NewChecker(&CheckerOptions{
+		ManifestPath: testManifestPath,
+		BasePath:     testDataDir,
+		Fs:           fs,
+	})
 	require.NoError(t, err)
 
 	ctx, cancel := context.WithCancel(context.Background())
@@ -419,10 +531,14 @@ func TestCheckNilChannels(t *testing.T) {
 
 	fs := afero.NewMemMapFs()
 	files := map[string][]byte{testFileName: []byte("data")}
-	createTestManifest(t, fs, "/manifest.mf", files)
+	createTestManifest(t, fs, testManifestPath, files)
 	createFilesOnDisk(t, fs, files)
 
-	chk, err := NewChecker("/manifest.mf", "/data", fs)
+	chk, err := NewChecker(&CheckerOptions{
+		ManifestPath: testManifestPath,
+		BasePath:     testDataDir,
+		Fs:           fs,
+	})
 	require.NoError(t, err)
 
 	// Should not panic with nil channels
@@ -435,10 +551,14 @@ func TestFindExtraFilesNilChannel(t *testing.T) {
 
 	fs := afero.NewMemMapFs()
 	files := map[string][]byte{testFileName: []byte("data")}
-	createTestManifest(t, fs, "/manifest.mf", files)
+	createTestManifest(t, fs, testManifestPath, files)
 	createFilesOnDisk(t, fs, files)
 
-	chk, err := NewChecker("/manifest.mf", "/data", fs)
+	chk, err := NewChecker(&CheckerOptions{
+		ManifestPath: testManifestPath,
+		BasePath:     testDataDir,
+		Fs:           fs,
+	})
 	require.NoError(t, err)
 
 	// Should not panic with nil channel
@@ -455,7 +575,7 @@ func TestCheckSubdirectories(t *testing.T) {
 		"dir1/dir2/file2.txt":     []byte("content2"),
 		"dir1/dir2/dir3/deep.txt": []byte("deep content"),
 	}
-	createTestManifest(t, fs, "/manifest.mf", files)
+	createTestManifest(t, fs, testManifestPath, files)
 
 	// Create files with full directory structure
 	for path, content := range files {
@@ -465,7 +585,11 @@ func TestCheckSubdirectories(t *testing.T) {
 		require.NoError(t, afero.WriteFile(fs, fullPath, content, 0o644))
 	}
 
-	chk, err := NewChecker("/manifest.mf", "/data", fs)
+	chk, err := NewChecker(&CheckerOptions{
+		ManifestPath: testManifestPath,
+		BasePath:     testDataDir,
+		Fs:           fs,
+	})
 	require.NoError(t, err)
 
 	results := make(chan Result, 10)
@@ -493,13 +617,17 @@ func TestCheckMissingFileDetectedWithoutFallback(t *testing.T) {
 		testExistsFile: []byte("here"),
 		"missing.txt":  []byte("not on disk"),
 	}
-	createTestManifest(t, fs, "/manifest.mf", files)
+	createTestManifest(t, fs, testManifestPath, files)
 	// Only create one file on disk
 	createFilesOnDisk(t, fs, map[string][]byte{
 		testExistsFile: []byte("here"),
 	})
 
-	chk, err := NewChecker("/manifest.mf", "/data", fs)
+	chk, err := NewChecker(&CheckerOptions{
+		ManifestPath: testManifestPath,
+		BasePath:     testDataDir,
+		Fs:           fs,
+	})
 	require.NoError(t, err)
 
 	results := make(chan Result, 10)
@@ -537,7 +665,11 @@ func TestFindExtraFilesSkipsDotfiles(t *testing.T) {
 	require.NoError(t,
 		afero.WriteFile(fs, "/data/.git/config", []byte("git config"), 0o644))
 
-	chk, err := NewChecker("/data/.index.mf", "/data", fs)
+	chk, err := NewChecker(&CheckerOptions{
+		ManifestPath: "/data/.index.mf",
+		BasePath:     testDataDir,
+		Fs:           fs,
+	})
 	require.NoError(t, err)
 
 	results := make(chan Result, 10)
@@ -566,7 +698,11 @@ func TestFindExtraFilesSkipsManifestFile(t *testing.T) {
 	createTestManifest(t, fs, "/data/index.mf", files)
 	createFilesOnDisk(t, fs, files)
 
-	chk, err := NewChecker("/data/index.mf", "/data", fs)
+	chk, err := NewChecker(&CheckerOptions{
+		ManifestPath: "/data/index.mf",
+		BasePath:     testDataDir,
+		Fs:           fs,
+	})
 	require.NoError(t, err)
 
 	results := make(chan Result, 10)
@@ -587,9 +723,13 @@ func TestCheckEmptyManifest(t *testing.T) {
 
 	fs := afero.NewMemMapFs()
 	// Create manifest with no files
-	createTestManifest(t, fs, "/manifest.mf", map[string][]byte{})
+	createTestManifest(t, fs, testManifestPath, map[string][]byte{})
 
-	chk, err := NewChecker("/manifest.mf", "/data", fs)
+	chk, err := NewChecker(&CheckerOptions{
+		ManifestPath: testManifestPath,
+		BasePath:     testDataDir,
+		Fs:           fs,
+	})
 	require.NoError(t, err)
 
 	assert.Equal(t, FileCount(0), chk.FileCount())
@@ -621,10 +761,14 @@ func TestCheckProgressRateLimited(t *testing.T) {
 		files[name] = []byte("content")
 	}
 
-	createTestManifest(t, fs, "/manifest.mf", files)
+	createTestManifest(t, fs, testManifestPath, files)
 	createFilesOnDisk(t, fs, files)
 
-	chk, err := NewChecker("/manifest.mf", "/data", fs)
+	chk, err := NewChecker(&CheckerOptions{
+		ManifestPath: testManifestPath,
+		BasePath:     testDataDir,
+		Fs:           fs,
+	})
 	require.NoError(t, err)
 
 	results := make(chan Result, 200)

mfer/deserialize.go

@@ -352,16 +352,29 @@ func NewManifestFromReader(input io.Reader) (*manifest, error) {
 	return m, nil
 }
 
-// NewManifestFromFile reads a manifest from a file path using the given filesystem.
-// If fs is nil, the real filesystem (OsFs) is used.
+// ManifestFromFileOptions configures NewManifestFromFile.
+type ManifestFromFileOptions struct {
+	// Path is the manifest file to read (required).
+	Path string
+	// Fs is the filesystem to use, defaults to OsFs if nil.
+	Fs afero.Fs
+}
+
+// NewManifestFromFile reads a manifest from a file. It returns an error if
+// opts is nil or its path is empty.
 //
 //nolint:revive // unexported-return: exporting manifest is owner question 13
-func NewManifestFromFile(fs afero.Fs, path string) (*manifest, error) {
+func NewManifestFromFile(opts *ManifestFromFileOptions) (*manifest, error) {
+	if opts == nil || opts.Path == "" {
+		return nil, errManifestPathEmpty
+	}
+
+	fs := opts.Fs
 	if fs == nil {
 		fs = afero.NewOsFs()
 	}
 
-	f, err := fs.Open(path)
+	f, err := fs.Open(opts.Path)
 	if err != nil {
 		return nil, err
 	}

mfer/mf.proto.sha256

@@ -0,0 +1 @@
+103901c42b94396aa7ae128fd503ef693a4b7a03b2169481f25fda3d2c254e00  mf.proto

mfer/mf_test.go

@@ -0,0 +1,29 @@
+package mfer_test
+
+import (
+	"crypto/sha256"
+	"encoding/hex"
+	"os"
+	"strings"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+// mf.pb.go is generated from mf.proto and committed. `make generate`
+// records the hash of the mf.proto it generated from in mf.proto.sha256.
+func TestGeneratedCodeMatchesProto(t *testing.T) {
+	t.Parallel()
+
+	proto, err := os.ReadFile("mf.proto")
+	require.NoError(t, err)
+
+	recorded, err := os.ReadFile("mf.proto.sha256")
+	require.NoError(t, err)
+
+	recordedHash, _, _ := strings.Cut(string(recorded), " ")
+	sum := sha256.Sum256(proto)
+	require.Equal(t, recordedHash, hex.EncodeToString(sum[:]),
+		"mfer/mf.proto has changed since mfer/mf.pb.go was generated "+
+			"from it: run `make generate` and commit the result")
+}

script/fmt

@@ -5,19 +5,8 @@ set -eu
 SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd -P)"
 ROOT="$(cd "$SCRIPT_DIR/.." && pwd -P)"
 
-# Regenerate mfer/mf.pb.go from mfer/mf.proto if it is missing or stale
-# (mirrors the old Makefile prerequisite; the generated file is
-# committed, so this is normally a no-op).
-ensure_pb() {
-    if [ ! -f mfer/mf.pb.go ] ||
-        [ -n "$(find mfer/mf.proto -newer mfer/mf.pb.go 2>/dev/null)" ]; then
-        (cd mfer && go generate .)
-    fi
-}
-
 main() {
     cd "$ROOT"
-    ensure_pb
     gofumpt -l -w mfer internal cmd
     # Markdown and JSON, over the same file set script/fmt-check verifies.
     "$SCRIPT_DIR/prettier" --write

script/fmt-check-go

@@ -6,19 +6,8 @@ set -eu
 
 ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"
 
-# Regenerate mfer/mf.pb.go from mfer/mf.proto if it is missing or stale
-# (mirrors the old Makefile prerequisite; the generated file is
-# committed, so this is normally a no-op).
-ensure_pb() {
-    if [ ! -f mfer/mf.pb.go ] ||
-        [ -n "$(find mfer/mf.proto -newer mfer/mf.pb.go 2>/dev/null)" ]; then
-        (cd mfer && go generate .)
-    fi
-}
-
 main() {
     cd "$ROOT"
-    ensure_pb
     if [ -n "$(gofmt -l .)" ]; then
         echo "gofmt: files need formatting:" >&2
         gofmt -l . >&2

script/generate

@@ -0,0 +1,52 @@
+#!/bin/sh
+# script/generate: regenerate mfer/mf.pb.go from mfer/mf.proto, and record
+# the hash of that mf.proto in mfer/mf.proto.sha256. Nothing else
+# regenerates mf.pb.go: it is committed, so building and checking need no
+# protoc. A test fails while mf.proto no longer matches the recorded hash.
+#
+# Needs exactly the protoc and protoc-gen-go versions named in the header of
+# the committed mf.pb.go (README.md says how to install them). Another
+# version writes a different mf.pb.go, so the script refuses to run.
+set -eu
+
+ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"
+
+# protoc 33.4 names itself v6.33.4 in the mf.pb.go header.
+PROTOC_VERSION="33.4"
+PROTOC_GEN_GO_VERSION="v1.36.11"
+
+# require_version <command> <its exact --version output>
+require_version() {
+    actual="$("$1" --version 2>/dev/null || true)"
+    if [ "$actual" != "$2" ]; then
+        echo "generate: needs $2 on PATH, found: ${actual:-none}" >&2
+        echo "  README.md says how to install it." >&2
+        exit 1
+    fi
+}
+
+# sha256 <file>: print "<hash>  <file>", with sha256sum, or with shasum
+# where there is no sha256sum.
+sha256() {
+    if command -v sha256sum >/dev/null 2>&1; then
+        sha256sum "$1"
+    elif command -v shasum >/dev/null 2>&1; then
+        shasum -a 256 "$1"
+    else
+        echo "generate: needs sha256sum or shasum on PATH" >&2
+        exit 1
+    fi
+}
+
+main() {
+    cd "$ROOT/mfer"
+    require_version protoc "libprotoc $PROTOC_VERSION"
+    require_version protoc-gen-go "protoc-gen-go $PROTOC_GEN_GO_VERSION"
+    # Hashed before regenerating, so a missing hash tool stops the script
+    # before it changes anything. Regenerating leaves mf.proto as it is.
+    proto_hash="$(sha256 mf.proto)"
+    go generate .
+    echo "$proto_hash" >mf.proto.sha256
+}
+
+main "$@"

script/test

@@ -4,19 +4,8 @@ set -eu
 
 ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"
 
-# Regenerate mfer/mf.pb.go from mfer/mf.proto if it is missing or stale
-# (mirrors the old Makefile prerequisite; the generated file is
-# committed, so this is normally a no-op).
-ensure_pb() {
-    if [ ! -f mfer/mf.pb.go ] ||
-        [ -n "$(find mfer/mf.proto -newer mfer/mf.pb.go 2>/dev/null)" ]; then
-        (cd mfer && go generate .)
-    fi
-}
-
 main() {
     cd "$ROOT"
-    ensure_pb
     go test -timeout 30s -race -cover ./... ||
         {
             echo "--- Rerunning with -v for details ---"