Go indexer: Handle resolution of the 'unsafe' metapackage.

Summary:
The type checker does not include "unsafe" as a package dependency, since it
isn't a real package but a special hook for the compiler. For indexing purposes
we pretend it IS s real package so that references will resolve.

- Extractor: Don't treat 'unsafe' as a missing package.
- Add a unit test for resolution of the 'unsafe' package.
- Add ForStandardLibrary to the govname package.

Reviewers: #core_team, shahms

Reviewed By: #core_team, shahms

Differential Revision: https://phabricator-dot-kythe-repo.appspot.com/D1256

kythe/go/extractors/golang/golang.go

@@ -450,10 +450,11 @@ func (*Package) addFlag(cu *apb.CompilationUnit, name string, values ...string)
 func (p *Package) addDeps(cu *apb.CompilationUnit, importPaths []string) []string {
 	var missing []string
 	for _, ip := range importPaths {
-		dep, err := p.ext.addPackage(ip)
-		if err != nil {
+		if ip == "unsafe" {
+			// package unsafe is intrinsic; nothing to do
+		} else if dep, err := p.ext.addPackage(ip); err != nil {
 			missing = append(missing, ip)
-		} else if ip != "unsafe" { // package unsafe is intrinsic
+		} else {
 			p.addInput(cu, dep)
 		}
 	}

kythe/go/extractors/govname/BUILD

@@ -15,6 +15,7 @@ go_package_library(
 
 go_test(
     name = "govname_test",
+    size = "small",
     srcs = ["govname_test.go"],
     library = "govname",
     visibility = ["//visibility:private"],

kythe/go/extractors/govname/govname.go

@@ -109,6 +109,17 @@ func ForBuiltin(signature string) *spb.VName {
 	}
 }
 
+// ForStandardLibrary returns a VName for a standard library package with the
+// given import path.
+func ForStandardLibrary(importPath string) *spb.VName {
+	return &spb.VName{
+		Corpus:    golangCorpus,
+		Language:  Language,
+		Path:      importPath,
+		Signature: "package",
+	}
+}
+
 // IsStandardLibrary reports whether v names part of the Go standard library.
 // This includes the "golang.org" corpus but excludes the "golang.org/x/..."
 // extension repositories.  If v == nil, the answer is false.

kythe/go/extractors/govname/govname_test.go

@@ -100,3 +100,22 @@ func TestForBuiltin(t *testing.T) {
 		t.Errorf("ForBuiltin(%q): got %+v, want %+v", signature, got, want)
 	}
 }
+
+func TestForStandardLibrary(t *testing.T) {
+	tests := []struct {
+		input string
+		want  *spb.VName
+	}{
+		{"fmt", &spb.VName{Corpus: "golang.org", Path: "fmt", Signature: "package", Language: "go"}},
+		{"io/ioutil", &spb.VName{Corpus: "golang.org", Path: "io/ioutil", Signature: "package", Language: "go"}},
+		{"strconv", &spb.VName{Corpus: "golang.org", Path: "strconv", Signature: "package", Language: "go"}},
+	}
+	for _, test := range tests {
+		got := ForStandardLibrary(test.input)
+		if !proto.Equal(got, test.want) {
+			t.Errorf("ForStandardLibrary(%q): got %+v\nwant %+v", test.input, got, test.want)
+		} else if !IsStandardLibrary(got) {
+			t.Errorf("IsStandardLibrary(%+v) is unexpectedly false", got)
+		}
+	}
+}

kythe/go/indexer/BUILD

@@ -93,3 +93,8 @@ go_indexer_test(
     name = "comment_test",
     srcs = ["testdata/basic/comments.go"],
 )
+
+go_indexer_test(
+    name = "unsafe_test",
+    srcs = ["testdata/unsafe.go"],
+)

kythe/go/indexer/indexer.go

@@ -123,6 +123,11 @@ type packageImporter struct {
 func (pi *packageImporter) Import(importPath string) (*types.Package, error) {
 	if pkg := pi.deps[importPath]; pkg != nil && pkg.Complete() {
 		return pkg, nil
+	} else if importPath == "unsafe" {
+		// The "unsafe" package is special, and isn't usually added by the
+		// resolver into the dependency map.
+		pi.deps[importPath] = types.Unsafe
+		return types.Unsafe, nil
 	}
 
 	// Fetch the required input holding the package for this import path, and
@@ -235,6 +240,9 @@ func Resolve(unit *apb.CompilationUnit, f Fetcher, info *types.Info) (*PackageIn
 			pi.PackageVName[pkg].Signature = "package"
 		}
 	}
+	if _, ok := pi.Dependencies["unsafe"]; ok {
+		pi.PackageVName[types.Unsafe] = govname.ForStandardLibrary("unsafe")
+	}
 
 	// Set this package's own vname.
 	pi.VName = proto.Clone(unit.VName).(*spb.VName)

kythe/go/indexer/testdata/unsafe.go

@@ -0,0 +1,11 @@
+// Package magic tests resolution of the "unsafe" metapackage.
+package magic
+
+//- @"\"unsafe\"" ref/imports Unsafe=vname("package", "golang.org", _, "unsafe", "go")
+import "unsafe"
+
+//- @foo defines/binding Foo
+//- Foo.node/kind variable
+//- @unsafe ref Unsafe
+//- @Pointer ref UnsafePointer
+var foo unsafe.Pointer