go/analysis/internal/analysisflags: print Diagnostic.Related too

+ script test

Change-Id: Ic4c4dd6afcbe0268848ce37ce450000863b565e9
Reviewed-on: https://go-review.googlesource.com/c/tools/+/692515
Auto-Submit: Alan Donovan <[email protected]>
Reviewed-by: Robert Findley <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>

Author: adonovan

go/analysis/internal/analysisflags/flags.go

@@ -318,24 +318,32 @@ var vetLegacyFlags = map[string]string{
 // If contextLines is nonnegative, it also prints the
 // offending line plus this many lines of context.
 func PrintPlain(out io.Writer, fset *token.FileSet, contextLines int, diag analysis.Diagnostic) {
-	posn := fset.Position(diag.Pos)
-	fmt.Fprintf(out, "%s: %s\n", posn, diag.Message)
-
-	// show offending line plus N lines of context.
-	if contextLines >= 0 {
-		posn := fset.Position(diag.Pos)
-		end := fset.Position(diag.End)
-		if !end.IsValid() {
-			end = posn
-		}
-		data, _ := os.ReadFile(posn.Filename)
-		lines := strings.Split(string(data), "\n")
-		for i := posn.Line - contextLines; i <= end.Line+contextLines; i++ {
-			if 1 <= i && i <= len(lines) {
-				fmt.Fprintf(out, "%d\t%s\n", i, lines[i-1])
+	print := func(pos, end token.Pos, message string) {
+		posn := fset.Position(pos)
+		fmt.Fprintf(out, "%s: %s\n", posn, message)
+
+		// show offending line plus N lines of context.
+		if contextLines >= 0 {
+			end := fset.Position(end)
+			if !end.IsValid() {
+				end = posn
+			}
+			// TODO(adonovan): highlight the portion of the line indicated
+			// by pos...end using ASCII art, terminal colors, etc?
+			data, _ := os.ReadFile(posn.Filename)
+			lines := strings.Split(string(data), "\n")
+			for i := posn.Line - contextLines; i <= end.Line+contextLines; i++ {
+				if 1 <= i && i <= len(lines) {
+					fmt.Fprintf(out, "%d\t%s\n", i, lines[i-1])
+				}
 			}
 		}
 	}
+
+	print(diag.Pos, diag.End, diag.Message)
+	for _, rel := range diag.Related {
+		print(rel.Pos, rel.End, "\t"+rel.Message)
+	}
 }
 
 // A JSONTree is a mapping from package ID to analysis name to result.

go/analysis/internal/checker/fix_test.go

@@ -42,6 +42,7 @@ func TestMain(m *testing.M) {
 			markerAnalyzer,
 			noendAnalyzer,
 			renameAnalyzer,
+			relatedAnalyzer,
 		)
 		panic("unreachable")
 	}
@@ -587,6 +588,25 @@ var noendAnalyzer = &analysis.Analyzer{
 	},
 }
 
+var relatedAnalyzer = &analysis.Analyzer{
+	Name: "related",
+	Doc:  "reports a Diagnostic with RelatedInformaiton",
+	Run: func(pass *analysis.Pass) (any, error) {
+		decl := pass.Files[0].Decls[0]
+		pass.Report(analysis.Diagnostic{
+			Pos:     decl.Pos(),
+			End:     decl.Pos() + 1,
+			Message: "decl starts here",
+			Related: []analysis.RelatedInformation{{
+				Message: "decl ends here",
+				Pos:     decl.End() - 1,
+				End:     decl.End(),
+			}},
+		})
+		return nil, nil
+	},
+}
+
 // panics asserts that f() panics with with a value whose printed form matches the regexp want.
 func panics(t *testing.T, want string, f func()) {
 	defer func() {

go/analysis/internal/checker/testdata/plain.txt

@@ -0,0 +1,25 @@
+# Test plain output.
+#
+# File slashes assume non-Windows.
+skip GOOS=windows
+
+checker -related example.com/p
+stderr p/p.go:3:1: decl starts here
+stderr p/p.go:4:1: 	decl ends here
+
+checker -related -c=0 example.com/p
+stderr p/p.go:3:1: decl starts here
+stderr 3	func f\(bar int\) {
+stderr p/p.go:4:1: 	decl ends here
+stderr 4	}
+exit 3
+
+-- go.mod --
+module example.com
+go 1.22
+
+-- p/p.go --
+package p
+
+func f(bar int) {
+}