Add -lint=suggest to include replacement in --format=json output

buildifier/config/config.go

@@ -102,7 +102,7 @@ type Config struct {
 	Mode string `json:"mode,omitempty"`
 	// DiffMode is an alias for
 	DiffMode bool `json:"diffMode,omitempty"`
-	// Lint determines the lint mode: off, warn, or fix (default off)
+	// Lint determines the lint mode: off, warn, suggest, or fix (default off)
 	Lint string `json:"lint,omitempty"`
 	// Warnings is a comma-separated list of warning identifiers used in the lint mode or "all"
 	Warnings string `json:"warnings,omitempty"`
@@ -201,7 +201,7 @@ func (c *Config) Validate(args []string) error {
 		return err
 	}
 
-	if err := ValidateModes(&c.Mode, &c.Lint, &c.DiffMode); err != nil {
+	if err := ValidateModes(&c.Mode, &c.Lint, &c.DiffMode, &c.Format); err != nil {
 		return err
 	}
 

buildifier/config/validation.go

@@ -60,7 +60,7 @@ func isRecognizedMode(validModes []string, mode string) bool {
 }
 
 // ValidateModes validates flags --mode, --lint, and -d
-func ValidateModes(mode, lint *string, dflag *bool, additionalModes ...string) error {
+func ValidateModes(mode, lint *string, dflag *bool, format *string) error {
 	if *dflag {
 		if *mode != "" {
 			return fmt.Errorf("cannot specify both -d and -mode flags")
@@ -70,7 +70,6 @@ func ValidateModes(mode, lint *string, dflag *bool, additionalModes ...string) e
 
 	// Check mode.
 	validModes := []string{"check", "diff", "fix", "print_if_changed"}
-	validModes = append(validModes, additionalModes...)
 
 	if *mode == "" {
 		*mode = "fix"
@@ -91,6 +90,11 @@ func ValidateModes(mode, lint *string, dflag *bool, additionalModes ...string) e
 			return fmt.Errorf("--lint=fix is only compatible with --mode=fix")
 		}
 
+	case "suggest":
+		if *format != "json" {
+			return fmt.Errorf("--lint=suggest is only compatible with --format=json")
+		}
+
 	default:
 		return fmt.Errorf("unrecognized lint mode %s; valid modes are warn and fix", *lint)
 	}

buildifier/utils/diagnostics.go

@@ -19,9 +19,10 @@ package utils
 import (
 	"encoding/json"
 	"fmt"
+	"strings"
+
 	"github.com/bazelbuild/buildtools/build"
 	"github.com/bazelbuild/buildtools/warn"
-	"strings"
 )
 
 // Diagnostics contains diagnostic information returned by formatter and linter
@@ -74,20 +75,27 @@ type FileDiagnostics struct {
 }
 
 type warning struct {
-	Start       position `json:"start"`
-	End         position `json:"end"`
-	Category    string   `json:"category"`
-	Actionable  bool     `json:"actionable"`
-	AutoFixable bool     `json:"autoFixable"`
-	Message     string   `json:"message"`
-	URL         string   `json:"url"`
+	Start       position     `json:"start"`
+	End         position     `json:"end"`
+	Category    string       `json:"category"`
+	Actionable  bool         `json:"actionable"`
+	AutoFixable bool         `json:"autoFixable"`
+	Message     string       `json:"message"`
+	URL         string       `json:"url"`
+	Replacement *replacement `json:"replacement"` // Optional replacement
 }
 
 type position struct {
 	Line   int `json:"line"`
 	Column int `json:"column"`
 }
 
+type replacement struct {
+	Start   int    `json:"start"`   // Start offset in bytes
+	End     int    `json:"end"`     // End offset in bytes, may be equal to Start for insertions
+	Content string `json:"content"` // Replacement content
+}
+
 // NewDiagnostics returns a new Diagnostics object
 func NewDiagnostics(fileDiagnostics ...*FileDiagnostics) *Diagnostics {
 	diagnostics := &Diagnostics{
@@ -121,6 +129,7 @@ func NewFileDiagnostics(filename string, warnings []*warn.Finding) *FileDiagnost
 			AutoFixable: w.AutoFixable,
 			Message:     w.Message,
 			URL:         w.URL,
+			Replacement: makeReplacement(w.Replacement),
 		})
 	}
 
@@ -147,3 +156,14 @@ func makePosition(p build.Position) position {
 		Column: p.LineRune,
 	}
 }
+
+func makeReplacement(r *warn.Replacement) *replacement {
+	if r == nil {
+		return nil
+	}
+	return &replacement{
+		Start:   r.Start,
+		End:     r.End,
+		Content: r.Content,
+	}
+}

buildifier/utils/utils.go

@@ -131,6 +131,8 @@ func Lint(f *build.File, lint string, warningsList *[]string, verbose bool) []*w
 	switch lint {
 	case "warn":
 		return warn.FileWarnings(f, *warningsList, nil, warn.ModeWarn, fileReader)
+	case "suggest":
+		return warn.FileWarnings(f, *warningsList, nil, warn.ModeSuggest, fileReader)
 	case "fix":
 		warn.FixWarnings(f, *warningsList, verbose, fileReader)
 	}