doctree/indexer: ensure data directory is versioned too

This gives us one global version number we can use. In the worst case
scenario, if lots of people adopt doctree v0.1 and we need to change
the data directory drastically we could detect this version number and
wipe out the entire dir upon upgrade.

Signed-off-by: Stephen Gutekanst <[email protected]>

doctree/indexer/indexer.go

@@ -220,6 +220,11 @@ type AutoIndexedProject struct {
 func RunIndexers(ctx context.Context, dir string, dataDirFlag, projectFlag *string) error {
 	var err error
 
+	// Ensure the doctree data dir exists, and that it has a version file.
+	if err := ensureDataDir(*dataDirFlag); err != nil {
+		return errors.Wrap(err, "ensureDataDir")
+	}
+
 	// IndexDir may partially complete, with some indexers succeeding while others fail. In this
 	// case indexes and indexErr are both != nil.
 	indexes, indexErr := IndexDir(ctx, dir)
@@ -247,13 +252,8 @@ func RunIndexers(ctx context.Context, dir string, dataDirFlag, projectFlag *stri
 		err = multierror.Append(err, errors.Wrap(searchErr, "IndexForSearch"))
 	}
 
-	// Write a version number file. This enables us in future versions of doctree to, say,
-	// automatically re-index (or just remove) directories from old versions that do not match the
-	// new indexing/schema format.
-	//
-	// The version number is a simple incrementing integer, starting at 1. It has no relation to
-	// doctree release versions.
-	versionErr := os.WriteFile(filepath.Join(projectDir, "version"), []byte("1"), 0o666)
+	// Write a version number file.
+	versionErr := os.WriteFile(filepath.Join(projectDir, "version"), []byte(projectDirVersion), 0o666)
 	if versionErr != nil {
 		if rmErr := os.RemoveAll(projectDir); rmErr != nil {
 			err = multierror.Append(err, errors.Wrap(rmErr, "RemoveAll"))
@@ -263,3 +263,38 @@ func RunIndexers(ctx context.Context, dir string, dataDirFlag, projectFlag *stri
 
 	return err
 }
+
+// The version stored in e.g. ~/.doctree/index/<project>/version - indicating the version of the
+// project directory. If we need to change search indexing, add support for more languages, etc.
+// this file is how we'd determine which directories need to be re-indexed / removed.
+//
+// An incrementing integer. No relation to other version numbers.
+const projectDirVersion = "1"
+
+// The version stored in e.g. ~/.doctree/version - indicating the version of the overall data
+// directory. If we need to change the directory structure in some way, change the autoindex file
+// format, etc. this is what we'd use to determine when to do that.
+//
+// An incrementing integer. No relation to other version numbers.
+const dataDirVersion = "1"
+
+func ensureDataDir(dataDir string) error {
+	versionFile := filepath.Join(dataDir, "version")
+	fi, err := os.Stat(versionFile)
+	if os.IsNotExist(err) {
+		// Create the directory if needed.
+		if err := os.MkdirAll(dataDir, os.ModePerm); err != nil {
+			return errors.Wrap(err, "MkdirAll")
+		}
+
+		// Write the version info.
+		return os.WriteFile(versionFile, []byte(dataDirVersion), 0o666)
+	}
+	if err != nil {
+		return err
+	}
+	if !fi.IsDir() {
+		return errors.New("not a directory")
+	}
+	return nil
+}