Propagate lint report write errors

cmd/core-lint/main.go

@@ -323,7 +323,9 @@ func newCheckCommand() *cli.Command {
 			}
 			return lintpkg.WriteReportSARIF(command.OutOrStdout(), report)
 		default:
-			lintpkg.WriteText(command.OutOrStdout(), findings)
+			if err := lintpkg.WriteText(command.OutOrStdout(), findings); err != nil {
+				return err
+			}
 			if format == "text" && len(findings) > 0 {
 				writeCatalogSummary(command.OutOrStdout(), findings)
 			}
@@ -405,11 +407,9 @@ func writeReport(writer io.Writer, output string, report lintpkg.Report) error {
 	case "json":
 		return lintpkg.WriteReportJSON(writer, report)
 	case "text":
-		lintpkg.WriteReportText(writer, report)
-		return nil
+		return lintpkg.WriteReportText(writer, report)
 	case "github":
-		lintpkg.WriteReportGitHub(writer, report)
-		return nil
+		return lintpkg.WriteReportGitHub(writer, report)
 	case "sarif":
 		return lintpkg.WriteReportSARIF(writer, report)
 	default:

pkg/lint/report.go

@@ -75,7 +75,7 @@ func WriteJSONL(w io.Writer, findings []Finding) error {
 // WriteText writes findings in a human-readable format.
 //
 //	lint.WriteText(os.Stdout, findings)
-func WriteText(w io.Writer, findings []Finding) {
+func WriteText(w io.Writer, findings []Finding) error {
 	for _, finding := range findings {
 		message := finding.Message
 		if message == "" {
@@ -85,8 +85,11 @@ func WriteText(w io.Writer, findings []Finding) {
 		if code == "" {
 			code = finding.RuleID
 		}
-		fmt.Fprintf(w, "%s:%d [%s] %s (%s)\n", finding.File, finding.Line, finding.Severity, message, code)
+		if _, err := fmt.Fprintf(w, "%s:%d [%s] %s (%s)\n", finding.File, finding.Line, finding.Severity, message, code); err != nil {
+			return err
+		}
 	}
+	return nil
 }
 
 // WriteReportJSON writes the RFC report document as pretty-printed JSON.
@@ -101,15 +104,18 @@ func WriteReportJSON(w io.Writer, report Report) error {
 // WriteReportText writes report findings followed by a short summary.
 //
 //	lint.WriteReportText(os.Stdout, report)
-func WriteReportText(w io.Writer, report Report) {
-	WriteText(w, report.Findings)
-	fmt.Fprintf(w, "\n%d finding(s): %d error(s), %d warning(s), %d info\n", report.Summary.Total, report.Summary.Errors, report.Summary.Warnings, report.Summary.Info)
+func WriteReportText(w io.Writer, report Report) error {
+	if err := WriteText(w, report.Findings); err != nil {
+		return err
+	}
+	_, err := fmt.Fprintf(w, "\n%d finding(s): %d error(s), %d warning(s), %d info\n", report.Summary.Total, report.Summary.Errors, report.Summary.Warnings, report.Summary.Info)
+	return err
 }
 
 // WriteReportGitHub writes GitHub Actions annotation lines.
 //
 //	lint.WriteReportGitHub(os.Stdout, report)
-func WriteReportGitHub(w io.Writer, report Report) {
+func WriteReportGitHub(w io.Writer, report Report) error {
 	for _, finding := range report.Findings {
 		level := githubAnnotationLevel(finding.Severity)
 
@@ -132,8 +138,11 @@ func WriteReportGitHub(w io.Writer, report Report) {
 		if code == "" {
 			code = finding.RuleID
 		}
-		fmt.Fprintf(w, "::%s%s::[%s] %s (%s)\n", level, location, finding.Tool, message, code)
+		if _, err := fmt.Fprintf(w, "::%s%s::[%s] %s (%s)\n", level, location, finding.Tool, message, code); err != nil {
+			return err
+		}
 	}
+	return nil
 }
 
 // WriteReportSARIF writes a minimal SARIF document for code scanning tools.

pkg/lint/report_test.go

@@ -3,6 +3,7 @@ package lint
 import (
 	"bytes"
 	"encoding/json"
+	"errors"
 	"strings"
 	"testing"
 
@@ -118,7 +119,8 @@ func TestWriteJSONL_Good_Empty(t *testing.T) {
 func TestWriteText_Good(t *testing.T) {
 	findings := sampleFindings()
 	var buf bytes.Buffer
-	WriteText(&buf, findings)
+	err := WriteText(&buf, findings)
+	require.NoError(t, err)
 
 	output := buf.String()
 	assert.Contains(t, output, "store/query.go:42")
@@ -131,14 +133,15 @@ func TestWriteText_Good(t *testing.T) {
 
 func TestWriteText_Good_Empty(t *testing.T) {
 	var buf bytes.Buffer
-	WriteText(&buf, nil)
+	err := WriteText(&buf, nil)
+	require.NoError(t, err)
 	assert.Empty(t, buf.String())
 }
 
 func TestWriteReportGitHub_Good_MapsInfoToNotice(t *testing.T) {
 	var buf bytes.Buffer
 
-	WriteReportGitHub(&buf, Report{
+	err := WriteReportGitHub(&buf, Report{
 		Findings: []Finding{{
 			Tool:     "demo",
 			File:     "example.go",
@@ -149,10 +152,23 @@ func TestWriteReportGitHub_Good_MapsInfoToNotice(t *testing.T) {
 			Message:  "explanation",
 		}},
 	})
+	require.NoError(t, err)
 
 	assert.Contains(t, buf.String(), "::notice file=example.go,line=7,col=3::[demo] explanation (demo-rule)")
 }
 
+func TestWriteText_Bad_PropagatesWriterErrors(t *testing.T) {
+	err := WriteText(failingWriter{}, sampleFindings())
+	require.Error(t, err)
+}
+
+func TestWriteReportGitHub_Bad_PropagatesWriterErrors(t *testing.T) {
+	err := WriteReportGitHub(failingWriter{}, Report{
+		Findings: sampleFindings(),
+	})
+	require.Error(t, err)
+}
+
 func TestWriteReportSARIF_Good_MapsInfoToNote(t *testing.T) {
 	var buf bytes.Buffer
 
@@ -176,3 +192,9 @@ func TestWriteReportSARIF_Good_MapsInfoToNote(t *testing.T) {
 	results := runs[0].(map[string]any)["results"].([]any)
 	assert.Equal(t, "note", results[0].(map[string]any)["level"])
 }
+
+type failingWriter struct{}
+
+func (failingWriter) Write([]byte) (int, error) {
+	return 0, errors.New("write failed")
+}