Emit diagnostic to pass fourth integration tests

Author: owen-mc

go/extractor/diagnostics/diagnostics.go

@@ -143,3 +143,13 @@ func EmitNewerGoVersionNeeded() {
 		"", 0, 0, 0, 0,
 	)
 }
+
+func EmitGoFilesFoundButNotProcessed() {
+	emitDiagnostic("go/autobuilder/go-files-found-but-not-processed",
+		"Go files were found but not processed",
+		"[Specify a custom build command](https://docs.github.com/en/github-ae@latest/code-security/code-scanning/automatically-scanning-your-code-for-vulnerabilities-and-errors/configuring-the-codeql-workflow-for-compiled-languages#adding-build-steps-for-a-compiled-language) that includes one or more `go build` commands to build the `.go` files to be analyzed.",
+		severityError, false,
+		true, true, true,
+		"", 0, 0, 0, 0,
+	)
+}

go/extractor/extractor.go

@@ -98,6 +98,15 @@ func ExtractWithFlags(buildFlags []string, patterns []string) error {
 
 	if len(pkgs) == 0 {
 		log.Println("No packages found.")
+
+		wd, err := os.Getwd()
+		if err != nil {
+			log.Fatalf("Unable to determine current directory: %s\n", err.Error())
+		}
+
+		if util.FindGoFiles(wd) {
+			diagnostics.EmitGoFilesFoundButNotProcessed()
+		}
 	}
 
 	log.Println("Extracting universe scope.")

go/extractor/util/util.go

@@ -4,6 +4,7 @@ import (
 	"encoding/json"
 	"errors"
 	"io"
+	"io/fs"
 	"log"
 	"os"
 	"os/exec"
@@ -281,3 +282,17 @@ func EscapeTrapSpecialChars(s string) string {
 	s = strings.ReplaceAll(s, "#", "#")
 	return s
 }
+
+func FindGoFiles(root string) bool {
+	found := false
+	filepath.WalkDir(root, func(s string, d fs.DirEntry, e error) error {
+		if e != nil {
+			return e
+		}
+		if filepath.Ext(d.Name()) == ".go" {
+			found = true
+		}
+		return nil
+	})
+	return found
+}