formatter: remove sole-return block blanks

Remove existing blank lines before a sole return in control-statement
bodies. This makes the blank-line rule idempotent for guard clauses
whose wrapped return call is the only statement in the block.

Keep the multiline function-signature exception intact by limiting the
cleanup to if, for, and range bodies. Preserve leading-comment return
separators and refresh self-formatting touched by the new rule.

Author: bhandras

dsl/action.go

@@ -2885,7 +2885,6 @@ func callAlreadyAcceptableWithMultilineLiteralArg(ctx *Context,
 		return false
 	}
 	if !callHasDirectMultilineLiteralArg(ctx, call) {
-
 		return false
 	}
 
@@ -4855,7 +4854,6 @@ func (a *BreakInterfaceMethodAction) Execute(caps Captures, ctx *Context) (
 		method, indent, ctx.ColumnLimit, ctx.TabStop, a.FormatFunc,
 		func(signature, indent string, colLimit, tabStop int) (string,
 			bool) {
-
 			return formatMethodSimple(
 				signature, indent, colLimit, tabStop,
 			), false
@@ -5109,6 +5107,16 @@ func (c *blankLineBatchContext) inspectFile(file *ast.File) {
 				}
 
 			case *ast.ReturnStmt:
+				if onlyStmtInBlockWithoutLeadingComment(
+					c.ctx, n,
+				) {
+
+					start := c.ctx.Fset.Position(n.Pos()).Offset
+					c.maybeRemoveBlankBeforeLineStart(
+						lineStart(c.ctx.Source, start),
+					)
+					break
+				}
 				if c.returnCond.Eval(caps, c.ctx) {
 					c.maybeInsertBlankBefore(n)
 				}
@@ -5132,6 +5140,25 @@ func (c *blankLineBatchContext) inspectFile(file *ast.File) {
 	)
 }
 
+func (c *blankLineBatchContext) maybeRemoveBlankBeforeLineStart(
+	lineStartIdx int) {
+
+	if lineStartIdx <= 0 || lineStartIdx > len(c.ctx.Source) {
+		return
+	}
+	if !hasBlankLineBeforeLineStart(c.ctx.Source, lineStartIdx) {
+		return
+	}
+
+	prevLineEnd := lineStartIdx - 1
+	prevStart := lineStart(c.ctx.Source, prevLineEnd)
+	if prevStart < 0 || prevStart > lineStartIdx {
+		return
+	}
+
+	c.b.Delete(prevStart, lineStartIdx)
+}
+
 // parseCheckOK performs a defensive parse check on the output.
 func parseCheckOK(out []byte) bool {
 	fset := token.NewFileSet()

dsl/composite_lit_expand_action.go

@@ -218,7 +218,6 @@ func (a *BreakCompositeKeyValueAction) Execute(caps Captures, ctx *Context) (
 
 	orig := string(ctx.Source[start:end])
 	if orig == "" || hasLineComment(orig) || hasBlockComment(orig) {
-
 		return nil, false
 	}
 

dsl/condition.go

@@ -2113,18 +2113,8 @@ func (c *IsReturnNeedingBlankCond) Eval(caps Captures, ctx *Context) bool {
 	if !ok {
 		return false
 	}
-	if block, ok := ctx.Parent(node).(*ast.BlockStmt); ok &&
-		block != nil && len(block.List) == 1 && block.List[0] == node {
-
-		brace := ctx.Fset.Position(block.Lbrace).Offset
-		returnStart := ctx.Fset.Position(node.Pos()).Offset
-		if brace >= 0 && brace+1 <= returnStart {
-			gap := string(ctx.Source[brace+1 : returnStart])
-			if !strings.Contains(gap, "//") &&
-				!strings.Contains(gap, "/*") {
-				return false
-			}
-		}
+	if onlyStmtInBlockWithoutLeadingComment(ctx, node) {
+		return false
 	}
 
 	pos := ctx.Fset.Position(node.Pos())
@@ -2175,6 +2165,30 @@ func (c *IsReturnNeedingBlankCond) Eval(caps Captures, ctx *Context) bool {
 	return true
 }
 
+func onlyStmtInBlockWithoutLeadingComment(ctx *Context, node ast.Node) bool {
+	block, ok := ctx.Parent(node).(*ast.BlockStmt)
+	if !ok || block == nil || len(block.List) != 1 ||
+		block.List[0] != node {
+		return false
+	}
+	switch ctx.Parent(block).(type) {
+	case *ast.IfStmt, *ast.ForStmt, *ast.RangeStmt:
+
+	default:
+		return false
+	}
+
+	brace := ctx.Fset.Position(block.Lbrace).Offset
+	nodeStart := ctx.Fset.Position(node.Pos()).Offset
+	if brace < 0 || brace+1 > nodeStart {
+		return false
+	}
+
+	gap := string(ctx.Source[brace+1 : nodeStart])
+
+	return !strings.Contains(gap, "//") && !strings.Contains(gap, "/*")
+}
+
 // IsIfErrReturnNeedingBlankCond checks if an `if err != nil { return ... }`
 // statement should be preceded by a blank line for readability.
 //

dsl/edit.go

@@ -58,7 +58,6 @@ func ApplyEdits(src []byte, edits []Edit) ([]byte, error) {
 // single-span replacement case.
 func ApplySingleEdit(src []byte, start, end int,
 	replace []byte) ([]byte, error) {
-
 	return ApplyEdits(
 		src, []Edit{
 			{Start: start, End: end, Replace: replace},

dsl/engine_edit_action_test.go

@@ -24,7 +24,6 @@ type replaceIdentEditAction struct {
 
 func (a *replaceIdentEditAction) Execute(caps Captures, ctx *Context) ([]byte,
 	bool) {
-
 	return nil, false
 }
 
@@ -55,7 +54,6 @@ type overlappingEditAction struct{}
 
 func (a *overlappingEditAction) Execute(caps Captures, ctx *Context) ([]byte,
 	bool) {
-
 	return nil, false
 }
 

dsl/engine_ownership_block_test.go

@@ -22,7 +22,6 @@ func (a fixedEditAction) Execute(caps Captures, ctx *Context) ([]byte, bool) {
 
 func (a fixedEditAction) ExecuteEdits(caps Captures, ctx *Context) ([]Edit,
 	bool, error) {
-
 	return []Edit{
 		{
 			Start:   a.start,

dsl/layout/doc.go

@@ -90,18 +90,15 @@ type IndentByCols struct {
 }
 
 func (IndentByCols) isDoc() {}
-
-func T(s string) Doc { return Text(s) }
-func L() Doc         { return Line{} }
-func SL() Doc        { return SoftLine{} }
-func FB() Doc        { return ForceBreak{} }
-func G(d Doc) Doc    { return Group{Doc: d} }
+func T(s string) Doc        { return Text(s) }
+func L() Doc                { return Line{} }
+func SL() Doc               { return SoftLine{} }
+func FB() Doc               { return ForceBreak{} }
+func G(d Doc) Doc           { return Group{Doc: d} }
 func N(indent string, d Doc) Doc {
 	return Nest{Indent: indent, Doc: d}
 }
-
-func C(docs ...Doc) Doc { return Concat(docs) }
-
+func C(docs ...Doc) Doc       { return Concat(docs) }
 func IB(broken, flat Doc) Doc { return IfBreak{Broken: broken, Flat: flat} }
 func A(d Doc) Doc             { return Align{Doc: d} }
 func I(cols int, d Doc) Doc   { return IndentByCols{Cols: cols, Doc: d} }

dsl/rules.go

@@ -1499,7 +1499,6 @@ func LegacyMultiLineScanRules(scanFunc LegacyMultiLineScanFunc) []Rule {
 // LegacyMultiLineScanRules.
 func LegacyMultiLineScanRulesWithOptions(opts MultiLineCallOptions,
 	scanFunc LegacyMultiLineScanFunc) []Rule {
-
 	return []Rule{
 		{
 			Name: "legacy_multiline_scan",
@@ -1540,7 +1539,6 @@ func LegacyCompactCallRules(formatFunc LegacyCompactCallFormatFunc) []Rule {
 // LegacyCommentRules delegates comment formatting to a legacy formatter.
 func LegacyCommentRules(formatFunc LegacyCommentFormatFunc,
 	moveInlineAbove bool) []Rule {
-
 	return []Rule{
 		{
 			Name: "legacy_comment_format",
@@ -1618,7 +1616,6 @@ func LegacyBlankLinesRules(formatFunc LegacyBlankLinesFormatFunc) []Rule {
 // source cannot be parsed, or as a last resort after native DSL rules).
 func LegacyBlankLinesFallbackRules(
 	formatFunc LegacyBlankLinesFormatFunc) []Rule {
-
 	return []Rule{
 		{
 			Name: "legacy_blank_lines_fallback",

dsl/types.go

@@ -108,7 +108,6 @@ type Context struct {
 // NewContext creates a new formatting context.
 func NewContext(fset *token.FileSet, source []byte, columnLimit,
 	tabStop int) *Context {
-
 	return &Context{
 		Fset:        fset,
 		Source:      source,

formatter/compact_call_formatter.go

@@ -2195,7 +2195,6 @@ func isDirectCompositeLiteralExpr(expr ast.Expr) bool {
 // at word boundaries when possible.
 func buildSplitQuoted(text string, startCol int, contIndent string,
 	width int) string {
-
 	return buildSplitQuotedWithOptions(
 		text, startCol, contIndent, width, false,
 	)
@@ -2206,7 +2205,6 @@ func buildSplitQuoted(text string, startCol int, contIndent string,
 // appears as a call argument that may have trailing arguments.
 func buildSplitQuotedForCallArg(text string, startCol int, contIndent string,
 	width int, hasTrailingArgs bool) string {
-
 	return buildSplitQuotedWithOptions(
 		text, startCol, contIndent, width, hasTrailingArgs,
 	)
@@ -4023,7 +4021,6 @@ func FormatCallPackedMultiLine(call []byte, wsIndent string, colLimit,
 // selected.
 func FormatCallPackedMultiLineNext(call []byte, wsIndent string, colLimit,
 	ts int) string {
-
 	return FormatCallPackedMultiLineNextWithPrefix(
 		call, wsIndent, wsIndent, colLimit, ts,
 	)