add a format arg

go/analysis/passes/printf/printf.go

@@ -9,6 +9,7 @@ import (
 	_ "embed"
 	"fmt"
 	"go/ast"
+	"go/constant"
 	"go/token"
 	"go/types"
 	"reflect"
@@ -452,7 +453,7 @@ func checkPrintf(pass *analysis.Pass, kind Kind, call *ast.CallExpr, name string
 		return
 	}
 	formatArg := call.Args[idx]
-	format, ok := fmtstr.StringConstantExpr(pass.TypesInfo, formatArg)
+	format, ok := stringConstantExpr(pass.TypesInfo, formatArg)
 	if !ok {
 		// Format string argument is non-constant.
 
@@ -486,7 +487,11 @@ func checkPrintf(pass *analysis.Pass, kind Kind, call *ast.CallExpr, name string
 		}
 		return
 	}
-	directives, err := fmtstr.ParsePrintf(pass.TypesInfo, call)
+
+	// Pass the string constant value so
+	// fmt.Sprintf("%"+("s"), "hi", 3) can be reported as
+	// "fmt.Sprintf call needs 1 arg but has 2 args".
+	directives, err := fmtstr.ParsePrintf(pass.TypesInfo, call, format)
 	if err != nil {
 		pass.ReportRangef(call.Fun, "%s %s", name, err.Error())
 		return
@@ -856,7 +861,7 @@ func checkPrint(pass *analysis.Pass, call *ast.CallExpr, name string) {
 	}
 
 	arg := args[0]
-	if s, ok := fmtstr.StringConstantExpr(pass.TypesInfo, arg); ok {
+	if s, ok := stringConstantExpr(pass.TypesInfo, arg); ok {
 		// Ignore trailing % character
 		// The % in "abc 0.0%" couldn't be a formatting directive.
 		s = strings.TrimSuffix(s, "%")
@@ -870,7 +875,7 @@ func checkPrint(pass *analysis.Pass, call *ast.CallExpr, name string) {
 	if strings.HasSuffix(name, "ln") {
 		// The last item, if a string, should not have a newline.
 		arg = args[len(args)-1]
-		if s, ok := fmtstr.StringConstantExpr(pass.TypesInfo, arg); ok {
+		if s, ok := stringConstantExpr(pass.TypesInfo, arg); ok {
 			if strings.HasSuffix(s, "\n") {
 				pass.ReportRangef(call, "%s arg list ends with redundant newline", name)
 			}
@@ -886,6 +891,17 @@ func checkPrint(pass *analysis.Pass, call *ast.CallExpr, name string) {
 	}
 }
 
+// StringConstantExpr returns expression's string constant value.
+//
+// ("", false) is returned if expression isn't a string constant.
+func stringConstantExpr(info *types.Info, expr ast.Expr) (string, bool) {
+	lit := info.Types[expr].Value
+	if lit != nil && lit.Kind() == constant.String {
+		return constant.StringVal(lit), true
+	}
+	return "", false
+}
+
 // count(n, what) returns "1 what" or "N whats"
 // (assuming the plural of what is whats).
 func count(n int, what string) string {

gopls/internal/golang/highlight.go

@@ -80,9 +80,9 @@ func highlightPath(info *types.Info, path []ast.Node, pos token.Pos) (map[posRan
 		if call, ok := node.(*ast.CallExpr); ok {
 			idx := fmtstr.FormatStringIndex(info, call)
 			if idx >= 0 && idx < len(call.Args) {
-				format, ok := fmtstr.StringConstantExpr(info, call.Args[idx])
-				if ok && strings.Contains(format, "%") {
-					highlightPrintf(info, call, call.Args[idx].Pos(), pos, result)
+				// We only care string literal, so fmt.Sprint("a"+"b%s", "bar") won't highlight.
+				if lit, ok := call.Args[idx].(*ast.BasicLit); ok && strings.Contains(lit.Value, "%") {
+					highlightPrintf(info, call, call.Args[idx].Pos(), pos, lit.Value, result)
 				}
 			}
 		}
@@ -157,18 +157,18 @@ func highlightPath(info *types.Info, path []ast.Node, pos token.Pos) (map[posRan
 //
 // If the cursor is on %s or name, highlightPrintf will highlight %s as a write operation,
 // and name as a read operation.
-func highlightPrintf(info *types.Info, call *ast.CallExpr, formatPos token.Pos, cursorPos token.Pos, result map[posRange]protocol.DocumentHighlightKind) {
-	directives, err := fmtstr.ParsePrintf(info, call)
+func highlightPrintf(info *types.Info, call *ast.CallExpr, formatPos token.Pos, cursorPos token.Pos, format string, result map[posRange]protocol.DocumentHighlightKind) {
+	directives, err := fmtstr.ParsePrintf(info, call, format)
 	if err != nil {
 		return
 	}
 
 	// highlightPair highlights the directive and its potential argument pair if the cursor is within either range.
 	highlightPair := func(start, end token.Pos, argIndex int) bool {
 		var (
-			rangeStart = formatPos + token.Pos(start) + 1 // add offset for leading '"'
-			rangeEnd   = formatPos + token.Pos(end) + 1   // add offset for leading '"'
-			arg        ast.Expr                           // may not exist
+			rangeStart = formatPos + token.Pos(start)
+			rangeEnd   = formatPos + token.Pos(end)
+			arg        ast.Expr // may not exist
 		)
 		if len(call.Args) > argIndex {
 			arg = call.Args[argIndex]

gopls/internal/test/marker/testdata/highlight/highlight_printf.txt

@@ -38,6 +38,11 @@ func SpecialChars() {
 	fmt.Printf("Hello \n %s, you \t \n have %d new messages!", "Alice", 5) //@hiloc(speciald, "%d", write),hiloc(specialargs1, "5", read),highlightall(speciald, specialargs1)
 }
 
+func Escaped() {
+	fmt.Printf("Hello %% \n %s, you \t%% \n have %d new m%%essages!", "Alice", 5) //@hiloc(escapeds, "%s", write),hiloc(escapedargs0, "\"Alice\"", read),highlightall(escapeds, escapedargs0)
+	fmt.Printf("Hello %% \n %s, you \t%% \n have %d new m%%essages!", "Alice", 5) //@hiloc(escapedd, "%s", write),hiloc(escapedargs1, "\"Alice\"", read),highlightall(escapedd, escapedargs1)
+}
+
 func Indexed() {
 	fmt.Printf("%[1]d", 3) //@hiloc(i1, "%[1]d", write),hiloc(i2, "3", read),highlightall(i1, i2)
 	fmt.Printf("%[1]*d", 3, 6) //@hiloc(i3, "[1]*", write),hiloc(i4, "3", read),hiloc(i5, "d", write),hiloc(i6, "6", read),highlightall(i3, i4),highlightall(i5, i6)

internal/fmtstr/parse.go

@@ -1,4 +1,4 @@
-// Copyright 2010 The Go Authors. All rights reserved.
+// Copyright 2024 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
@@ -7,7 +7,6 @@ package fmtstr
 import (
 	"fmt"
 	"go/ast"
-	"go/constant"
 	"go/types"
 	"strconv"
 	"strings"
@@ -67,23 +66,18 @@ type posRange struct {
 }
 
 // ParsePrintf takes a printf-like call expression,
-// extracts the format string, and parses out all format directives. Each
-// directive describes flags, width, precision, verb, and argument indexing.
-// This function returns a slice of parsed FormatDirective objects or an error
-// if parsing fails. It does not perform any validation of flags, verbs, and
-// existence of corresponding argument.
-//
-// Typical use case: Validate arguments passed to a Printf-like function call,
-// DocumentHighlight, Hover, or SemanticHighlight.
-func ParsePrintf(info *types.Info, call *ast.CallExpr) ([]*FormatDirective, error) {
+// extracts the format string, and parses out all format directives.
+// It returns a slice of parsed [FormatDirective] which describes
+// flags, width, precision, verb, and argument indexing, or an error
+// if parsing fails. It does not perform any validation of flags, verbs, nor the
+// existence of corresponding arguments.
+// The provided format may differ from the one in CallExpr, such as a concatenated string or a string
+// referred to by the argument in CallExpr.
+func ParsePrintf(info *types.Info, call *ast.CallExpr, format string) ([]*FormatDirective, error) {
 	idx := FormatStringIndex(info, call)
 	if idx < 0 || idx >= len(call.Args) {
 		return nil, fmt.Errorf("not a valid printf-like call")
 	}
-	format, ok := StringConstantExpr(info, call.Args[idx])
-	if !ok {
-		return nil, fmt.Errorf("non-constant format string")
-	}
 	if !strings.Contains(format, "%") {
 		return nil, fmt.Errorf("call has arguments but no formatting directives")
 	}
@@ -208,17 +202,6 @@ func FormatStringIndex(info *types.Info, call *ast.CallExpr) int {
 	return idx
 }
 
-// StringConstantExpr returns expression's string constant value.
-//
-// ("", false) is returned if expression isn't a string constant.
-func StringConstantExpr(info *types.Info, expr ast.Expr) (string, bool) {
-	lit := info.Types[expr].Value
-	if lit != nil && lit.Kind() == constant.String {
-		return constant.StringVal(lit), true
-	}
-	return "", false
-}
-
 // addOffset adjusts the recorded positions in Verb, Width, Prec, and the
 // directive's overall Range to be relative to the position in the full format string.
 func (s *FormatDirective) addOffset(parsedLen int) {