Implement diagnostic for relative package paths

Author: owen-mc

go/extractor/cli/go-extractor/go-extractor.go

@@ -9,6 +9,7 @@ import (
 	"strings"
 
 	"github.com/github/codeql-go/extractor"
+	"github.com/github/codeql-go/extractor/diagnostics"
 )
 
 var cpuprofile, memprofile string
@@ -115,7 +116,12 @@ func main() {
 	log.Printf("Build flags: '%s'; patterns: '%s'\n", strings.Join(buildFlags, " "), strings.Join(patterns, " "))
 	err := extractor.ExtractWithFlags(buildFlags, patterns)
 	if err != nil {
-		log.Fatalf("Error running go tooling: %s\n", err.Error())
+		errString := err.Error()
+		if strings.Contains(errString, "unexpected directory layout:") {
+			diagnostics.EmitRelativeImportPaths()
+		}
+
+		log.Fatalf("Error running go tooling: %s\n", errString)
 	}
 
 	if memprofile != "" {

go/extractor/diagnostics/diagnostics.go

@@ -181,3 +181,14 @@ func EmitGoFilesFoundButNotProcessed() {
 		noLocation,
 	)
 }
+
+func EmitRelativeImportPaths() {
+	emitDiagnostic(
+		"go/autobuilder/relative-import-paths",
+		"Some imports use unsupported relative package paths",
+		"You should replace relative package paths (that contain `.` or `..`) with absolute paths. Alternatively you can [use a Go module](https://go.dev/blog/using-go-modules).",
+		severityError,
+		fullVisibility,
+		noLocation,
+	)
+}