Merge pull request github#15361 from github/mbg/go/legacy-gopath-mode-deprecated

Go: Update autobuilder to deal with the upcoming deprecation of the legacy GOPATH mode

Author: mbg

go/extractor/autobuilder/autobuilder.go

@@ -70,12 +70,33 @@ func tryBuild(cmd string, args ...string) bool {
 	return res && (!CheckExtracted || checkExtractorRun())
 }
 
-// Autobuild attempts to detect build system and run the corresponding command.
+// If a project is accompanied by a build script (such as a makefile), then we try executing such
+// build scripts to build the project. This type represents pairs of script names to check for
+// and the names of corresponding build tools to invoke if those scripts exist.
+type BuildScript struct {
+	Tool     string // The name of the command to execute if the build script exists
+	Filename string // The name of the build script to check for
+}
+
+// An array of build scripts to check for and corresponding commands that we can execute
+// if they exist.
+var BuildScripts = []BuildScript{
+	{Tool: "make", Filename: "Makefile"},
+	{Tool: "make", Filename: "makefile"},
+	{Tool: "make", Filename: "GNUmakefile"},
+	{Tool: "ninja", Filename: "build.ninja"},
+	{Tool: "./build", Filename: "build"},
+	{Tool: "./build.sh", Filename: "build.sh"},
+}
+
+// Autobuild attempts to detect build systems based on the presence of build scripts from the
+// list in `BuildScripts` and run the corresponding command. This may invoke zero or more
+// build scripts in the order given by `BuildScripts`.
 func Autobuild() bool {
-	return tryBuildIfExists("Makefile", "make") ||
-		tryBuildIfExists("makefile", "make") ||
-		tryBuildIfExists("GNUmakefile", "make") ||
-		tryBuildIfExists("build.ninja", "ninja") ||
-		tryBuildIfExists("build", "./build") ||
-		tryBuildIfExists("build.sh", "./build.sh")
+	for _, script := range BuildScripts {
+		if tryBuildIfExists(script.Filename, script.Tool) {
+			return true
+		}
+	}
+	return false
 }

go/extractor/autobuilder/build-environment.go

@@ -267,15 +267,22 @@ func outputEnvironmentJson(version string) {
 // Get the version of Go to install and output it to stdout as json.
 func IdentifyEnvironment() {
 	var v versionInfo
-	buildInfo := project.GetBuildInfo(false)
-	goVersionInfo := project.TryReadGoDirective(buildInfo)
-	v.goModVersion, v.goModVersionFound = goVersionInfo.Version, goVersionInfo.Found
+	workspaces := project.GetWorkspaceInfo(false)
 
+	// Remove temporary extractor files (e.g. auto-generated go.mod files) when we are done
+	defer project.RemoveTemporaryExtractorFiles()
+
+	// Find the greatest Go version required by any of the workspaces.
+	greatestGoVersion := project.RequiredGoVersion(&workspaces)
+	v.goModVersion, v.goModVersionFound = greatestGoVersion.Version, greatestGoVersion.Found
+
+	// Find which, if any, version of Go is installed on the system already.
 	v.goEnvVersionFound = toolchain.IsInstalled()
 	if v.goEnvVersionFound {
 		v.goEnvVersion = toolchain.GetEnvGoVersion()[2:]
 	}
 
+	// Determine which version of Go we should recommend to install.
 	msg, versionToInstall := getVersionToInstall(v)
 	log.Println(msg)