cmd/go: reject missing source code in go get -d, same as go get -d -u

Fixes #11090.

Change-Id: I1518df7a48346b175ec80079a07225901fdd51fb
Reviewed-on: https://go-review.googlesource.com/12177Reviewed-by: Rob Pike <r@golang.org>

src/cmd/go/get.go

@@ -96,12 +96,13 @@ func runGet(cmd *Command, args []string) {
 	}
 
 	args = importPaths(args)
+	packagesForBuild(args)
 
 	// Phase 3.  Install.
 	if *getD {
 		// Download only.
 		// Check delayed until now so that importPaths
-		// has a chance to print errors.
+		// and packagesForBuild have a chance to print errors.
 		return
 	}
 

src/cmd/go/go_test.go

@@ -1184,6 +1184,22 @@ func TestGodocInstalls(t *testing.T) {
 	tg.wantExecutable(filepath.Join(goroot, "bin", "godoc"), "did not install godoc to $GOROOT/bin")
 }
 
+func TestGoGetNonPkg(t *testing.T) {
+	testenv.MustHaveExternalNetwork(t)
+
+	tg := testgo(t)
+	defer tg.cleanup()
+	tg.tempDir("gobin")
+	tg.setenv("GOPATH", tg.path("."))
+	tg.setenv("GOBIN", tg.path("gobin"))
+	tg.runFail("get", "-d", "golang.org/x/tools")
+	tg.grepStderr("golang.org/x/tools: no buildable Go source files", "missing error")
+	tg.runFail("get", "-d", "-u", "golang.org/x/tools")
+	tg.grepStderr("golang.org/x/tools: no buildable Go source files", "missing error")
+	tg.runFail("get", "-d", "golang.org/x/tools")
+	tg.grepStderr("golang.org/x/tools: no buildable Go source files", "missing error")
+}
+
 func TestInstalls(t *testing.T) {
 	tg := testgo(t)
 	defer tg.cleanup()