Fix printing keyword prefixes for definitions

experimental/ast/printer/bufformat_test.go

@@ -66,15 +66,6 @@ func TestBufFormat(t *testing.T) {
 		t.Run(relPath, func(t *testing.T) {
 			t.Parallel()
 
-			// editions/2024 is a parser error test corpus, not a
-			// printer test corpus: the proto files contain
-			// deliberately invalid edition syntax for the parser to
-			// diagnose. There is no formatted output to compare
-			// against.
-			if strings.Contains(relPath, "editions/2024") {
-				t.Skip("editions/2024 is a parser error test")
-			}
-
 			// deprecate/* requires adding `deprecated` options to
 			// existing declarations as an AST transform. The legacy
 			// formatter does this in buf's FormatModuleSet wrapper,

experimental/ast/printer/decl.go

@@ -91,6 +91,18 @@ func (p *printer) printImport(decl ast.DeclImport, gap gapStyle) {
 	p.printToken(decl.Semicolon(), p.semiGap())
 }
 
+// printDefPrefixes emits modifiers (optional/required/repeated/export/local)
+// that live on the underlying DeclDef's type chain. Def projections expose
+// only the bare keyword (`message`, `group`, etc.), so the prefixes have to
+// be drained from DeclDef before that keyword is printed.
+func (p *printer) printDefPrefixes(d ast.DeclDef, gap gapStyle) gapStyle {
+	for prefix := range d.Prefixes() {
+		p.printToken(prefix.PrefixToken(), gap)
+		gap = gapSpace
+	}
+	return gap
+}
+
 func (p *printer) printDef(decl ast.DeclDef, gap gapStyle) {
 	switch decl.Classify() {
 	case ast.DefKindOption:
@@ -153,42 +165,45 @@ func (p *printer) printOption(opt ast.DefOption, gap gapStyle) {
 }
 
 func (p *printer) printMessage(msg ast.DefMessage, gap gapStyle) {
+	gap = p.printDefPrefixes(msg.Decl, gap)
 	p.printToken(msg.Keyword, gap)
 	p.printPath(msg.Decl.Name(), gapSpace)
 	p.printBody(msg.Body)
 }
 
 func (p *printer) printEnum(e ast.DefEnum, gap gapStyle) {
+	gap = p.printDefPrefixes(e.Decl, gap)
 	p.printToken(e.Keyword, gap)
 	p.printPath(e.Decl.Name(), gapSpace)
 	p.printBody(e.Body)
 }
 
 func (p *printer) printService(svc ast.DefService, gap gapStyle) {
+	gap = p.printDefPrefixes(svc.Decl, gap)
 	p.printToken(svc.Keyword, gap)
 	p.printPath(svc.Decl.Name(), gapSpace)
 	p.printBody(svc.Body)
 }
 
 func (p *printer) printExtend(ext ast.DefExtend, gap gapStyle) {
+	gap = p.printDefPrefixes(ext.Decl, gap)
 	p.printToken(ext.Keyword, gap)
 	p.printPath(ext.Extendee, gapSpace)
 	p.printBody(ext.Body)
 }
 
 func (p *printer) printOneof(o ast.DefOneof, gap gapStyle) {
+	gap = p.printDefPrefixes(o.Decl, gap)
 	p.printToken(o.Keyword, gap)
 	p.printPath(o.Decl.Name(), gapSpace)
 	p.printBody(o.Body)
 }
 
 func (p *printer) printGroup(g ast.DefGroup, gap gapStyle) {
-	// Print type prefixes (optional/required/repeated) from the underlying
-	// DeclDef, since DefGroup.Keyword is the "group" keyword itself.
-	for prefix := range g.Decl.Prefixes() {
-		p.printToken(prefix.PrefixToken(), gap)
-		gap = gapSpace
-	}
+	// DefGroup.Keyword is the "group" keyword itself, so the modifiers
+	// (optional/required/repeated) sit on the underlying DeclDef's type
+	// chain rather than on the projection.
+	gap = p.printDefPrefixes(g.Decl, gap)
 
 	p.printToken(g.Keyword, gap)
 	p.printPath(g.Decl.Name(), gapSpace)