Send warning to client on CRLF line endings (#717)

In case either `opa-fmt` or `use-rego-v1` is enabled, we'll send back
a warning to the client whenever they save a document containing CRLF
line endings. This to avoid confusion when the user tries to fix formatting
using `opa fmt`, but the editor adding back CRLF line endings after.

Also disable the nestif linter, as it's annoying.

Fixes #693

Signed-off-by: Anders Eknert <anders@styra.com>

.golangci.yaml

@@ -18,6 +18,7 @@ linters:
     - rowserrcheck
     - wastedassign
     # annoying
+    - nestif
     - gocognit
     - goerr113
     - varnamelen

internal/lsp/documentsymbol.go

@@ -11,7 +11,6 @@ import (
 	"github.com/styrainc/regal/internal/lsp/types/symbols"
 )
 
-//nolint:nestif
 func documentSymbols(
 	contents string,
 	module *ast.Module,
@@ -173,7 +172,6 @@ func refToString(ref ast.Ref) string {
 	return sb.String()
 }
 
-//nolint:nestif
 func getRuleDetail(rule *ast.Rule) string {
 	if rule.Head.Args != nil {
 		return "function" + rule.Head.Args.String()

internal/lsp/documentsymbol_test.go

@@ -83,7 +83,6 @@ func TestRefToString(t *testing.T) {
 	}
 }
 
-//nolint:nestif
 func TestDocumentSymbols(t *testing.T) {
 	t.Parallel()
 

internal/lsp/server.go

@@ -27,6 +27,7 @@ import (
 	rparse "github.com/styrainc/regal/internal/parse"
 	"github.com/styrainc/regal/pkg/config"
 	"github.com/styrainc/regal/pkg/fixer/fixes"
+	"github.com/styrainc/regal/pkg/linter"
 )
 
 const (
@@ -114,6 +115,8 @@ func (l *LanguageServer) Handle(
 		return l.handleTextDocumentDidOpen(ctx, conn, req)
 	case "textDocument/didClose":
 		return struct{}{}, nil
+	case "textDocument/didSave":
+		return l.handleTextDocumentDidSave(ctx, conn, req)
 	case "textDocument/documentSymbol":
 		return l.handleTextDocumentDocumentSymbol(ctx, conn, req)
 	case "textDocument/didChange":
@@ -800,6 +803,56 @@ func (l *LanguageServer) handleTextDocumentDidChange(
 	return struct{}{}, nil
 }
 
+func (l *LanguageServer) handleTextDocumentDidSave(
+	ctx context.Context,
+	_ *jsonrpc2.Conn,
+	req *jsonrpc2.Request,
+) (result any, err error) {
+	var params types.TextDocumentDidSaveParams
+	if err := json.Unmarshal(*req.Params, &params); err != nil {
+		return nil, fmt.Errorf("failed to unmarshal params: %w", err)
+	}
+
+	if params.Text != nil && l.loadedConfig != nil {
+		if !strings.Contains(*params.Text, "\r\n") {
+			return struct{}{}, nil
+		}
+
+		enabled, err := linter.NewLinter().WithUserConfig(*l.loadedConfig).DetermineEnabledRules(ctx)
+		if err != nil {
+			l.logError(fmt.Errorf("failed to determine enabled rules: %w", err))
+
+			return struct{}{}, nil
+		}
+
+		formattingEnabled := false
+
+		for _, rule := range enabled {
+			if rule == "opa-fmt" || rule == "use-rego-v1" {
+				formattingEnabled = true
+
+				break
+			}
+		}
+
+		if formattingEnabled {
+			resp := types.ShowMessageParams{
+				Type:    2, // warning
+				Message: "CRLF line ending detected. Please change editor setting to use LF for line endings.",
+			}
+
+			err := l.conn.Notify(ctx, "window/showMessage", resp)
+			if err != nil {
+				l.logError(fmt.Errorf("failed to notify: %w", err))
+
+				return struct{}{}, nil
+			}
+		}
+	}
+
+	return struct{}{}, nil
+}
+
 func (l *LanguageServer) handleTextDocumentDocumentSymbol(
 	_ context.Context,
 	_ *jsonrpc2.Conn,
@@ -1037,6 +1090,9 @@ func (l *LanguageServer) handleInitialize(
 			TextDocumentSyncOptions: types.TextDocumentSyncOptions{
 				OpenClose: true,
 				Change:    1, // TODO: write logic to use 2, for incremental updates
+				Save: types.TextDocumentSaveOptions{
+					IncludeText: true,
+				},
 			},
 			DiagnosticProvider: types.DiagnosticOptions{
 				Identifier:            "rego",

internal/lsp/types/types.go

@@ -69,6 +69,11 @@ type GeneralClientCapabilities struct {
 	StaleRequestSupport StaleRequestSupportClientCapabilities `json:"staleRequestSupport"`
 }
 
+type ShowMessageParams struct {
+	Type    uint   `json:"type"`
+	Message string `json:"message"`
+}
+
 type StaleRequestSupportClientCapabilities struct {
 	Cancel                  bool     `json:"cancel"`
 	RetryOnContentModifieds []string `json:"retryOnContentModified"`
@@ -247,9 +252,19 @@ type TextDocumentInlayHintParams struct {
 	Range        Range                  `json:"range"`
 }
 
+type TextDocumentSaveOptions struct {
+	IncludeText bool `json:"includeText"`
+}
+
+type TextDocumentDidSaveParams struct {
+	TextDocument TextDocumentIdentifier `json:"textDocument"`
+	Text         *string                `json:"text,omitempty"`
+}
+
 type TextDocumentSyncOptions struct {
-	OpenClose bool `json:"openClose"`
-	Change    uint `json:"change"`
+	OpenClose bool                    `json:"openClose"`
+	Change    uint                    `json:"change"`
+	Save      TextDocumentSaveOptions `json:"save"`
 }
 
 type TextDocumentIdentifier struct {

pkg/reporter/reporter.go

@@ -94,7 +94,7 @@ func (tr PrettyReporter) Publish(_ context.Context, r report.Report) error {
 
 	footer := fmt.Sprintf("%d file%s linted.", r.Summary.FilesScanned, pluralScanned)
 
-	if r.Summary.NumViolations == 0 { //nolint:nestif
+	if r.Summary.NumViolations == 0 {
 		footer += " No violations found."
 	} else {
 		pluralViolations := ""
@@ -256,8 +256,6 @@ func (tr JSONReporter) Publish(_ context.Context, r report.Report) error {
 // Publish first prints the pretty formatted report to console for easy access in the logs. It then goes on
 // to print the GitHub Actions annotations for each violation. Finally, it prints a summary of the report suitable
 // for the GitHub Actions UI.
-//
-//nolint:nestif
 func (tr GitHubReporter) Publish(ctx context.Context, r report.Report) error {
 	err := NewPrettyReporter(tr.out).Publish(ctx, r)
 	if err != nil {
@@ -302,7 +300,7 @@ func (tr GitHubReporter) Publish(ctx context.Context, r report.Report) error {
 
 		fmt.Fprintf(summaryFile, "%d file%s linted.", r.Summary.FilesScanned, pluralScanned)
 
-		if r.Summary.NumViolations == 0 { //nolint:nestif
+		if r.Summary.NumViolations == 0 {
 			fmt.Fprintf(summaryFile, " No violations found")
 		} else {
 			pluralViolations := ""