lsp: Template new empty files & template on format (#1051)

* lsp: Template new empty files & template on format

Empty files will be created with a template content instead of being
an error.

New empty files will be immediately updated with the template content.

Some client operations will not trigger the new file event, so in such
cases, a save might be required to trigger the template update.

Fixes #1048

Signed-off-by: Charlie Egan <charlie@styra.com>

* lsp: Add test for server templating

Signed-off-by: Charlie Egan <charlie@styra.com>

---------

Signed-off-by: Charlie Egan <charlie@styra.com>

cmd/languageserver.go

@@ -45,6 +45,7 @@ func init() {
 			go ls.StartCommandWorker(ctx)
 			go ls.StartConfigWorker(ctx)
 			go ls.StartWorkspaceStateWorker(ctx)
+			go ls.StartTemplateWorker(ctx)
 
 			sigChan := make(chan os.Signal, 1)
 			signal.Notify(sigChan, os.Interrupt, syscall.SIGTERM)

internal/lsp/server.go

@@ -8,6 +8,8 @@ import (
 	"io"
 	"os"
 	"path/filepath"
+	"regexp"
+	"slices"
 	"strconv"
 	"strings"
 	"sync"
@@ -75,6 +77,7 @@ func NewLanguageServer(opts *LanguageServerOptions) *LanguageServer {
 		diagnosticRequestWorkspace: make(chan string, 10),
 		builtinsPositionFile:       make(chan fileUpdateEvent, 10),
 		commandRequest:             make(chan types.ExecuteCommandParams, 10),
+		templateFile:               make(chan fileUpdateEvent, 10),
 		configWatcher:              lsconfig.NewWatcher(&lsconfig.WatcherOpts{ErrorWriter: opts.ErrorLog}),
 		completionsManager:         completions.NewDefaultManager(c, store),
 	}
@@ -106,6 +109,7 @@ type LanguageServer struct {
 	diagnosticRequestWorkspace chan string
 	builtinsPositionFile       chan fileUpdateEvent
 	commandRequest             chan types.ExecuteCommandParams
+	templateFile               chan fileUpdateEvent
 }
 
 // fileUpdateEvent is sent to a channel when an update is required for a file.
@@ -732,6 +736,113 @@ func (l *LanguageServer) StartWorkspaceStateWorker(ctx context.Context) {
 	}
 }
 
+// StartTemplateWorker runs the process of the server that templates newly
+// created Rego files.
+func (l *LanguageServer) StartTemplateWorker(ctx context.Context) {
+	for {
+		select {
+		case <-ctx.Done():
+			return
+		case evt := <-l.templateFile:
+			newContents, err := l.templateContentsForFile(evt.URI)
+			if err != nil {
+				l.logError(fmt.Errorf("failed to template new file: %w", err))
+			}
+
+			// generate the edit params for the templating operation
+			templateParams := &types.ApplyWorkspaceEditParams{
+				Label: "Template new Rego file",
+				Edit: types.WorkspaceEdit{
+					DocumentChanges: []types.TextDocumentEdit{
+						{
+							TextDocument: types.OptionalVersionedTextDocumentIdentifier{URI: evt.URI},
+							Edits:        ComputeEdits("", newContents),
+						},
+					},
+				},
+			}
+
+			err = l.conn.Call(ctx, methodWorkspaceApplyEdit, templateParams, nil)
+			if err != nil {
+				l.logError(fmt.Errorf("failed %s notify: %v", methodWorkspaceApplyEdit, err.Error()))
+			}
+
+			// finally, update the cache contents and run diagnostics to clear
+			// empty module warning.
+			updateEvent := fileUpdateEvent{
+				Reason:  "internal/templateNewFile",
+				URI:     evt.URI,
+				Content: newContents,
+			}
+
+			l.diagnosticRequestFile <- updateEvent
+		}
+	}
+}
+
+func (l *LanguageServer) templateContentsForFile(fileURI string) (string, error) {
+	content, ok := l.cache.GetFileContents(fileURI)
+	if !ok {
+		return "", fmt.Errorf("failed to get file contents for URI %q", fileURI)
+	}
+
+	if content != "" {
+		return "", errors.New("file already has contents, templating not allowed")
+	}
+
+	path := uri.ToPath(l.clientIdentifier, fileURI)
+	dir := filepath.Dir(path)
+
+	roots, err := config.GetPotentialRoots(uri.ToPath(l.clientIdentifier, fileURI))
+	if err != nil {
+		return "", fmt.Errorf("failed to get potential roots during templating of new file: %w", err)
+	}
+
+	longestPrefixRoot := ""
+
+	for _, root := range roots {
+		if strings.HasPrefix(dir, root) && len(root) > len(longestPrefixRoot) {
+			longestPrefixRoot = root
+		}
+	}
+
+	if longestPrefixRoot == "" {
+		return "", fmt.Errorf("failed to find longest prefix root for templating of new file: %s", path)
+	}
+
+	parts := slices.Compact(strings.Split(strings.TrimPrefix(dir, longestPrefixRoot), string(os.PathSeparator)))
+
+	var pkg string
+
+	validPathComponentPattern := regexp.MustCompile(`^\w+[\w\-]*\w+$`)
+
+	for _, part := range parts {
+		if part == "" {
+			continue
+		}
+
+		if !validPathComponentPattern.MatchString(part) {
+			return "", fmt.Errorf("failed to template new file as package path contained invalid part: %s", part)
+		}
+
+		switch {
+		case strings.Contains(part, "-"):
+			pkg += fmt.Sprintf(`["%s"]`, part)
+		case pkg == "":
+			pkg += part
+		default:
+			pkg += "." + part
+		}
+	}
+
+	// if we are in the root, then we can use main as a default
+	if pkg == "" {
+		pkg = "main"
+	}
+
+	return fmt.Sprintf("package %s\n\nimport rego.v1\n", pkg), nil
+}
+
 func (l *LanguageServer) fixEditParams(
 	label string,
 	fix fixes.Fix,
@@ -1208,8 +1319,6 @@ func (l *LanguageServer) handleTextDocumentCodeLens(
 
 	module, ok := l.cache.GetModule(params.TextDocument.URI)
 	if !ok {
-		l.logError(fmt.Errorf("failed to get module for uri %q", params.TextDocument.URI))
-
 		// return a null response, as per the spec
 		return nil, nil
 	}
@@ -1597,8 +1706,6 @@ func (l *LanguageServer) handleTextDocumentDocumentSymbol(
 
 	module, ok := l.cache.GetModule(params.TextDocument.URI)
 	if !ok {
-		l.logError(fmt.Errorf("failed to get module for uri %q", params.TextDocument.URI))
-
 		return []types.DocumentSymbol{}, nil
 	}
 
@@ -1649,6 +1756,27 @@ func (l *LanguageServer) handleTextDocumentFormatting(
 		oldContent, ok = l.cache.GetFileContents(params.TextDocument.URI)
 	}
 
+	// if the file is empty, then the formatters will fail, so we template
+	// instead
+	if oldContent == "" {
+		newContent, err := l.templateContentsForFile(params.TextDocument.URI)
+		if err != nil {
+			return nil, fmt.Errorf("failed to template contents as a templating fallback: %w", err)
+		}
+
+		l.cache.ClearFileDiagnostics()
+
+		updateEvent := fileUpdateEvent{
+			Reason:  "internal/templateFormattingFallback",
+			URI:     params.TextDocument.URI,
+			Content: newContent,
+		}
+
+		l.diagnosticRequestFile <- updateEvent
+
+		return ComputeEdits(oldContent, newContent), nil
+	}
+
 	if !ok {
 		return nil, fmt.Errorf("failed to get file contents for uri %q", params.TextDocument.URI)
 	}
@@ -1773,6 +1901,7 @@ func (l *LanguageServer) handleWorkspaceDidCreateFiles(
 
 		l.diagnosticRequestFile <- evt
 		l.builtinsPositionFile <- evt
+		l.templateFile <- evt
 	}
 
 	return struct{}{}, nil

internal/lsp/server_template_test.go

@@ -0,0 +1,58 @@
+package lsp
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/styrainc/regal/internal/lsp/clients"
+	"github.com/styrainc/regal/internal/lsp/uri"
+)
+
+func TestServerTemplateContentsForFile(t *testing.T) {
+	t.Parallel()
+
+	s := NewLanguageServer(
+		&LanguageServerOptions{
+			ErrorLog: os.Stderr,
+		},
+	)
+
+	td := t.TempDir()
+
+	filePath := filepath.Join(td, "foo/bar/baz.rego")
+	regalPath := filepath.Join(td, ".regal/config.yaml")
+
+	initialState := map[string]string{
+		filePath:  "",
+		regalPath: "",
+	}
+
+	// create the initial state needed for the regal config root detection
+	for file := range initialState {
+		fileDir := filepath.Dir(file)
+
+		err := os.MkdirAll(fileDir, 0o755)
+		if err != nil {
+			t.Fatalf("unexpected error: %v", err)
+		}
+
+		err = os.WriteFile(file, []byte(""), 0o600)
+		if err != nil {
+			t.Fatalf("unexpected error: %v", err)
+		}
+	}
+
+	fileURI := uri.FromPath(clients.IdentifierGeneric, filePath)
+
+	s.cache.SetFileContents(fileURI, "")
+
+	newContents, err := s.templateContentsForFile(fileURI)
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+
+	if newContents != "package foo.bar\n\nimport rego.v1\n" {
+		t.Fatalf("unexpected contents: %v", newContents)
+	}
+}

pkg/config/config.go

@@ -195,7 +195,11 @@ func FindBundleRootDirectories(path string) ([]string, error) {
 
 	// This will traverse the tree **downwards** searching for .regal directories
 	// Not using rio.WalkFiles here as we're specifically looking for directories
-	if err := filepath.WalkDir(path, func(path string, info os.DirEntry, _ error) error {
+	if err := filepath.WalkDir(path, func(path string, info os.DirEntry, err error) error {
+		if err != nil {
+			return fmt.Errorf("failed to walk path: %w", err)
+		}
+
 		if info.IsDir() && info.Name() == regalDirName {
 			// Opening files as part of walking is generally not a good idea...
 			// but I think we can assume the number of .regal directories in a project