Improve indent detection

Author: fatanugraha

gopls/internal/lsp/source/lines.go

@@ -52,15 +52,29 @@ func splitLines(
 	_, _, _, target := findSplitGroupTarget(file, fset, start, end)
 
 	// get the original line indent of target.
+	firstLineIndent := getIndent(src, fset, target)
+	eltIndent := firstLineIndent + "\t"
+
+	return fset, processLines(fset, target, src, file, ",\n", "\n", ",\n"+firstLineIndent, eltIndent), nil
+}
+
+func getIndent(src []byte, fset *token.FileSet, target ast.Node) string {
+	var pos token.Pos
+	switch node := target.(type) {
+	case *ast.FieldList:
+		pos = node.Opening
+	case *ast.CallExpr:
+		pos = node.Lparen
+	case *ast.CompositeLit:
+		pos = node.Lbrace
+	}
+
 	split := bytes.Split(src, []byte("\n"))
-	targetLineNumber := safetoken.StartPosition(fset, target.Pos()).Line
+	targetLineNumber := safetoken.StartPosition(fset, pos).Line
 	firstLine := string(split[targetLineNumber-1])
 	trimmed := strings.TrimFunc(string(firstLine), unicode.IsSpace)
 
-	firstLineIndent := firstLine[:strings.Index(firstLine, trimmed)]
-	eltIndent := firstLineIndent + "\t"
-
-	return fset, processLines(fset, target, src, file, ",\n", "\n", ",\n"+firstLineIndent, eltIndent), nil
+	return firstLine[:strings.Index(firstLine, trimmed)]
 }
 
 func groupLines(
@@ -75,13 +89,7 @@ func groupLines(
 	return fset, processLines(fset, target, src, file, ", ", "", "", ""), nil
 }
 
-func processLines(
-	fset *token.FileSet,
-	target ast.Node,
-	src []byte,
-	file *ast.File,
-	sep, prefix, suffix, indent string,
-) *analysis.SuggestedFix {
+func processLines(fset *token.FileSet, target ast.Node, src []byte, file *ast.File, sep, prefix, suffix, indent string) *analysis.SuggestedFix {
 	var replPos, replEnd token.Pos
 	var lines []string
 

gopls/internal/test/marker/testdata/codeaction/splitlines.txt

@@ -118,6 +118,31 @@ func a() {
 	)) //@codeaction("hello", "hello", "refactor.rewrite", indent, "Split parameters into separate lines")
 }
 
+-- indent2/indent2.go --
+package indent2
+
+import "fmt"
+
+func a() {
+	fmt.
+		Println(1, 2, 3, fmt.Sprintf("hello %d", 4)) //@codeaction("1", "1", "refactor.rewrite", indent2, "Split parameters into separate lines")
+}
+
+-- @indent2/indent2/indent2.go --
+package indent2
+
+import "fmt"
+
+func a() {
+	fmt.
+		Println(
+			1,
+			2,
+			3,
+			fmt.Sprintf("hello %d", 4),
+		) //@codeaction("1", "1", "refactor.rewrite", indent2, "Split parameters into separate lines")
+}
+
 -- structelts/structelts.go --
 package structelts