Add DiagnosticsWriter interface to abstract over diagnostics output implementation

go/extractor/diagnostics/diagnostics.go

@@ -3,7 +3,7 @@ package diagnostics
 import (
 	"encoding/json"
 	"fmt"
-	"log"
+	"log/slog"
 	"os"
 	"strings"
 	"time"
@@ -56,19 +56,62 @@ type diagnostic struct {
 var diagnosticsEmitted, diagnosticsLimit uint = 0, 100
 var noDiagnosticDirPrinted bool = false
 
-func emitDiagnostic(sourceid, sourcename, markdownMessage string, severity diagnosticSeverity, visibility *visibilityStruct, location *locationStruct) {
+type DiagnosticsWriter interface {
+	WriteDiagnostic(d diagnostic)
+}
+
+type FileDiagnosticsWriter struct {
+	diagnosticDir string
+}
+
+func (writer *FileDiagnosticsWriter) WriteDiagnostic(d diagnostic) {
+	content, err := json.Marshal(d)
+	if err != nil {
+		slog.Error("Failed to encode diagnostic as JSON", slog.Any("err", err))
+		return
+	}
+
+	targetFile, err := os.CreateTemp(writer.diagnosticDir, "go-extractor.*.json")
+	if err != nil {
+		slog.Error("Failed to create diagnostic file", slog.Any("err", err))
+		return
+	}
+	defer func() {
+		if err := targetFile.Close(); err != nil {
+			slog.Error("Failed to close diagnostic file", slog.Any("err", err))
+		}
+	}()
+
+	_, err = targetFile.Write(content)
+	if err != nil {
+		slog.Error("Failed to write to diagnostic file", slog.Any("err", err))
+	}
+}
+
+var DefaultWriter *FileDiagnosticsWriter = nil
+
+func NewFileDiagnosticsWriter() *FileDiagnosticsWriter {
+	diagnosticDir := os.Getenv("CODEQL_EXTRACTOR_GO_DIAGNOSTIC_DIR")
+	if diagnosticDir == "" {
+		if !noDiagnosticDirPrinted {
+			slog.Warn("No diagnostic directory set, so not emitting diagnostics")
+			noDiagnosticDirPrinted = true
+		}
+		return nil
+	}
+
+	return &FileDiagnosticsWriter{diagnosticDir}
+}
+
+func init() {
+	DefaultWriter = NewFileDiagnosticsWriter()
+}
+
+// Emits a diagnostic using the specified `DiagnosticsWriter`.
+func emitDiagnosticTo(writer DiagnosticsWriter, sourceid, sourcename, markdownMessage string, severity diagnosticSeverity, visibility *visibilityStruct, location *locationStruct) {
 	if diagnosticsEmitted < diagnosticsLimit {
 		diagnosticsEmitted += 1
 
-		diagnosticDir := os.Getenv("CODEQL_EXTRACTOR_GO_DIAGNOSTIC_DIR")
-		if diagnosticDir == "" {
-			if !noDiagnosticDirPrinted {
-				log.Println("No diagnostic directory set, so not emitting diagnostic")
-				noDiagnosticDirPrinted = true
-			}
-			return
-		}
-
 		timestamp := time.Now().UTC().Format("2006-01-02T15:04:05.000") + "Z"
 
 		var d diagnostic
@@ -93,33 +136,18 @@ func emitDiagnostic(sourceid, sourcename, markdownMessage string, severity diagn
 			}
 		}
 
-		content, err := json.Marshal(d)
-		if err != nil {
-			log.Println(err)
-			return
-		}
-
-		targetFile, err := os.CreateTemp(diagnosticDir, "go-extractor.*.json")
-		if err != nil {
-			log.Println("Failed to create diagnostic file: ")
-			log.Println(err)
-			return
-		}
-		defer func() {
-			if err := targetFile.Close(); err != nil {
-				log.Println("Failed to close diagnostic file:")
-				log.Println(err)
-			}
-		}()
-
-		_, err = targetFile.Write(content)
-		if err != nil {
-			log.Println("Failed to write to diagnostic file: ")
-			log.Println(err)
-		}
+		writer.WriteDiagnostic(d)
 	}
 }
 
+// Emits a diagnostic using the default `DiagnosticsWriter`.
+func emitDiagnostic(sourceid, sourcename, markdownMessage string, severity diagnosticSeverity, visibility *visibilityStruct, location *locationStruct) {
+	if DefaultWriter == nil {
+		return
+	}
+	emitDiagnosticTo(DefaultWriter, sourceid, sourcename, markdownMessage, severity, visibility, location)
+}
+
 func EmitPackageDifferentOSArchitecture(pkgPath string) {
 	emitDiagnostic(
 		"go/autobuilder/package-different-os-architecture",