go.tools/importer: add unit test of LoadInitialPackages.

Also: fix nil pointer dereference during failed import of
non-first import path.

R=crawshaw
CC=golang-dev
https://golang.org/cl/13646043

importer/importer.go

@@ -189,7 +189,9 @@ func (imp *Importer) doImport0(imports map[string]*types.Package, path string) (
 		} else {
 			imp.importBinary(imports, ii)
 		}
-		ii.info.Importable = true
+		if ii.info != nil {
+			ii.info.Importable = true
+		}
 
 		close(ii.ready) // enter ready state and wake up waiters
 	} else {

importer/importer_test.go

@@ -0,0 +1,66 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package importer_test
+
+import (
+	"fmt"
+	"go/build"
+	"testing"
+
+	"code.google.com/p/go.tools/importer"
+)
+
+func TestLoadInitialPackages(t *testing.T) {
+	ctxt := &importer.Config{Build: &build.Default}
+
+	// Failed load: bad first import path causes parsePackageFiles to fail.
+	args := []string{"nosuchpkg", "errors"}
+	if _, _, err := importer.New(ctxt).LoadInitialPackages(args); err == nil {
+		t.Errorf("LoadInitialPackages(%q) succeeded, want failure", args)
+	} else {
+		// cannot find package: ok.
+	}
+
+	// Failed load: bad second import path proceeds to doImport0, which fails.
+	args = []string{"errors", "nosuchpkg"}
+	if _, _, err := importer.New(ctxt).LoadInitialPackages(args); err == nil {
+		t.Errorf("LoadInitialPackages(%q) succeeded, want failure", args)
+	} else {
+		// cannot find package: ok
+	}
+
+	// Successful load.
+	args = []string{"fmt", "errors", "testdata/a.go,testdata/b.go", "--", "surplus"}
+	imp := importer.New(ctxt)
+	infos, rest, err := imp.LoadInitialPackages(args)
+	if err != nil {
+		t.Errorf("LoadInitialPackages(%q) failed: %s", args, err)
+		return
+	}
+	if got, want := fmt.Sprint(rest), "[surplus]"; got != want {
+		t.Errorf("LoadInitialPackages(%q) rest: got %s, want %s", got, want)
+	}
+	// Check list of initial packages.
+	var pkgnames []string
+	for _, info := range infos {
+		pkgnames = append(pkgnames, info.Pkg.Path())
+	}
+	// Only the first import path (currently) contributes tests.
+	if got, want := fmt.Sprint(pkgnames), "[fmt fmt_test errors P]"; got != want {
+		t.Errorf("InitialPackages: got %s, want %s", got, want)
+	}
+	// Check set of transitive packages.
+	// There are >30 and the set may grow over time, so only check a few.
+	all := map[string]struct{}{}
+	for _, info := range imp.AllPackages() {
+		all[info.Pkg.Path()] = struct{}{}
+	}
+	want := []string{"strings", "time", "runtime", "testing", "unicode"}
+	for _, w := range want {
+		if _, ok := all[w]; !ok {
+			t.Errorf("AllPackages: want element %s, got set %v", w, all)
+		}
+	}
+}

importer/testdata/a.go

@@ -0,0 +1 @@
+package P

importer/testdata/b.go

@@ -0,0 +1 @@
+package P