cmd/go: apply import restrictions to test code too

We reject import of main packages, but we missed tests.
Reject in all tests except test of that main package.

We reject local (relative) imports from code with a
non-local import path, but again we missed tests.
Reject those too.

Fixes #14811.
Fixes #15795.
Fixes #17475.

Change-Id: I535ff26889520276a891904f54f1a85b2c40207d
Reviewed-on: https://go-review.googlesource.com/31821
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Quentin Smith <quentin@golang.org>

src/cmd/go/go_test.go

@@ -135,7 +135,15 @@ func testgo(t *testing.T) *testgoData {
 		t.Skip("skipping external tests on %s/%s", runtime.GOOS, runtime.GOARCH)
 	}
 
-	return &testgoData{t: t}
+	tg := &testgoData{t: t}
+
+	// Hide user's local .gitconfig from git invocations.
+	// In particular, people using Github 2FA may configure
+	// https://github.com/ to redirect to ssh://git@github.com/
+	// using an insteadOf configuration, and that will break various
+	// of our tests.
+	tg.setenv("HOME", "/test-go-home-does-not-exist")
+	return tg
 }
 
 // must gives a fatal error if err is not nil.
@@ -2063,6 +2071,16 @@ func TestCoverageUsesActualSettingToOverrideEvenForRace(t *testing.T) {
 	checkCoverage(tg, data)
 }
 
+func TestCoverageImportMainLoop(t *testing.T) {
+	tg := testgo(t)
+	defer tg.cleanup()
+	tg.setenv("GOPATH", filepath.Join(tg.pwd(), "testdata"))
+	tg.runFail("test", "importmain/test")
+	tg.grepStderr("not an importable package", "did not detect import main")
+	tg.runFail("test", "-cover", "importmain/test")
+	tg.grepStderr("not an importable package", "did not detect import main")
+}
+
 func TestBuildDryRunWithCgo(t *testing.T) {
 	if !canCgo {
 		t.Skip("skipping because cgo not enabled")
@@ -2462,21 +2480,238 @@ func TestGoGetHTTPS404(t *testing.T) {
 }
 
 // Test that you cannot import a main package.
-func TestIssue4210(t *testing.T) {
+// See golang.org/issue/4210 and golang.org/issue/17475.
+func TestImportMain(t *testing.T) {
 	tg := testgo(t)
 	defer tg.cleanup()
+
+	// Importing package main from that package main's test should work.
 	tg.tempFile("src/x/main.go", `package main
 		var X int
 		func main() {}`)
-	tg.tempFile("src/y/main.go", `package main
-		import "fmt"
+	tg.tempFile("src/x/main_test.go", `package main_test
 		import xmain "x"
-		func main() {
-			fmt.Println(xmain.X)
-		}`)
+		import "testing"
+		var _ = xmain.X
+		func TestFoo(t *testing.T) {}
+	`)
 	tg.setenv("GOPATH", tg.path("."))
-	tg.runFail("build", "y")
-	tg.grepBoth("is a program", `did not find expected error message ("is a program")`)
+	tg.run("build", "x")
+	tg.run("test", "x")
+
+	// Importing package main from another package should fail.
+	tg.tempFile("src/p1/p.go", `package p1
+		import xmain "x"
+		var _ = xmain.X
+	`)
+	tg.runFail("build", "p1")
+	tg.grepStderr("import \"x\" is a program, not an importable package", "did not diagnose package main")
+
+	// ... even in that package's test.
+	tg.tempFile("src/p2/p.go", `package p2
+	`)
+	tg.tempFile("src/p2/p_test.go", `package p2
+		import xmain "x"
+		import "testing"
+		var _ = xmain.X
+		func TestFoo(t *testing.T) {}
+	`)
+	tg.run("build", "p2")
+	tg.runFail("test", "p2")
+	tg.grepStderr("import \"x\" is a program, not an importable package", "did not diagnose package main")
+
+	// ... even if that package's test is an xtest.
+	tg.tempFile("src/p3/p.go", `package p
+	`)
+	tg.tempFile("src/p3/p_test.go", `package p_test
+		import xmain "x"
+		import "testing"
+		var _ = xmain.X
+		func TestFoo(t *testing.T) {}
+	`)
+	tg.run("build", "p3")
+	tg.runFail("test", "p3")
+	tg.grepStderr("import \"x\" is a program, not an importable package", "did not diagnose package main")
+
+	// ... even if that package is a package main
+	tg.tempFile("src/p4/p.go", `package main
+	func main() {}
+	`)
+	tg.tempFile("src/p4/p_test.go", `package main
+		import xmain "x"
+		import "testing"
+		var _ = xmain.X
+		func TestFoo(t *testing.T) {}
+	`)
+	tg.run("build", "p4")
+	tg.runFail("test", "p4")
+	tg.grepStderr("import \"x\" is a program, not an importable package", "did not diagnose package main")
+
+	// ... even if that package is a package main using an xtest.
+	tg.tempFile("src/p5/p.go", `package main
+	func main() {}
+	`)
+	tg.tempFile("src/p5/p_test.go", `package main_test
+		import xmain "x"
+		import "testing"
+		var _ = xmain.X
+		func TestFoo(t *testing.T) {}
+	`)
+	tg.run("build", "p5")
+	tg.runFail("test", "p5")
+	tg.grepStderr("import \"x\" is a program, not an importable package", "did not diagnose package main")
+}
+
+// Test that you cannot use a local import in a package
+// accessed by a non-local import (found in a GOPATH/GOROOT).
+// See golang.org/issue/17475.
+func TestImportLocal(t *testing.T) {
+	tg := testgo(t)
+	defer tg.cleanup()
+
+	// Importing package main from that package main's test should work.
+	tg.tempFile("src/dir/x/x.go", `package x
+		var X int
+	`)
+	tg.setenv("GOPATH", tg.path("."))
+	tg.run("build", "dir/x")
+
+	// Ordinary import should work.
+	tg.tempFile("src/dir/p0/p.go", `package p0
+		import "dir/x"
+		var _ = x.X
+	`)
+	tg.run("build", "dir/p0")
+
+	// Relative import should not.
+	tg.tempFile("src/dir/p1/p.go", `package p1
+		import "../x"
+		var _ = x.X
+	`)
+	tg.runFail("build", "dir/p1")
+	tg.grepStderr("local import.*in non-local package", "did not diagnose local import")
+
+	// ... even in a test.
+	tg.tempFile("src/dir/p2/p.go", `package p2
+	`)
+	tg.tempFile("src/dir/p2/p_test.go", `package p2
+		import "../x"
+		import "testing"
+		var _ = x.X
+		func TestFoo(t *testing.T) {}
+	`)
+	tg.run("build", "dir/p2")
+	tg.runFail("test", "dir/p2")
+	tg.grepStderr("local import.*in non-local package", "did not diagnose local import")
+
+	// ... even in an xtest.
+	tg.tempFile("src/dir/p2/p_test.go", `package p2_test
+		import "../x"
+		import "testing"
+		var _ = x.X
+		func TestFoo(t *testing.T) {}
+	`)
+	tg.run("build", "dir/p2")
+	tg.runFail("test", "dir/p2")
+	tg.grepStderr("local import.*in non-local package", "did not diagnose local import")
+
+	// Relative import starting with ./ should not work either.
+	tg.tempFile("src/dir/d.go", `package dir
+		import "./x"
+		var _ = x.X
+	`)
+	tg.runFail("build", "dir")
+	tg.grepStderr("local import.*in non-local package", "did not diagnose local import")
+
+	// ... even in a test.
+	tg.tempFile("src/dir/d.go", `package dir
+	`)
+	tg.tempFile("src/dir/d_test.go", `package dir
+		import "./x"
+		import "testing"
+		var _ = x.X
+		func TestFoo(t *testing.T) {}
+	`)
+	tg.run("build", "dir")
+	tg.runFail("test", "dir")
+	tg.grepStderr("local import.*in non-local package", "did not diagnose local import")
+
+	// ... even in an xtest.
+	tg.tempFile("src/dir/d_test.go", `package dir_test
+		import "./x"
+		import "testing"
+		var _ = x.X
+		func TestFoo(t *testing.T) {}
+	`)
+	tg.run("build", "dir")
+	tg.runFail("test", "dir")
+	tg.grepStderr("local import.*in non-local package", "did not diagnose local import")
+
+	// Relative import plain ".." should not work.
+	tg.tempFile("src/dir/x/y/y.go", `package dir
+		import ".."
+		var _ = x.X
+	`)
+	tg.runFail("build", "dir/x/y")
+	tg.grepStderr("local import.*in non-local package", "did not diagnose local import")
+
+	// ... even in a test.
+	tg.tempFile("src/dir/x/y/y.go", `package y
+	`)
+	tg.tempFile("src/dir/x/y/y_test.go", `package y
+		import ".."
+		import "testing"
+		var _ = x.X
+		func TestFoo(t *testing.T) {}
+	`)
+	tg.run("build", "dir/x/y")
+	tg.runFail("test", "dir/x/y")
+	tg.grepStderr("local import.*in non-local package", "did not diagnose local import")
+
+	// ... even in an x test.
+	tg.tempFile("src/dir/x/y/y_test.go", `package y_test
+		import ".."
+		import "testing"
+		var _ = x.X
+		func TestFoo(t *testing.T) {}
+	`)
+	tg.run("build", "dir/x/y")
+	tg.runFail("test", "dir/x/y")
+	tg.grepStderr("local import.*in non-local package", "did not diagnose local import")
+
+	// Relative import "." should not work.
+	tg.tempFile("src/dir/x/xx.go", `package x
+		import "."
+		var _ = x.X
+	`)
+	tg.runFail("build", "dir/x")
+	tg.grepStderr("local import.*in non-local package", "did not diagnose local import")
+
+	// ... even in a test.
+	tg.tempFile("src/dir/x/xx.go", `package x
+	`)
+	tg.tempFile("src/dir/x/xx_test.go", `package x
+		import "."
+		import "testing"
+		var _ = x.X
+		func TestFoo(t *testing.T) {}
+	`)
+	tg.run("build", "dir/x")
+	tg.runFail("test", "dir/x")
+	tg.grepStderr("local import.*in non-local package", "did not diagnose local import")
+
+	// ... even in an xtest.
+	tg.tempFile("src/dir/x/xx.go", `package x
+	`)
+	tg.tempFile("src/dir/x/xx_test.go", `package x_test
+		import "."
+		import "testing"
+		var _ = x.X
+		func TestFoo(t *testing.T) {}
+	`)
+	tg.run("build", "dir/x")
+	tg.runFail("test", "dir/x")
+	tg.grepStderr("local import.*in non-local package", "did not diagnose local import")
 }
 
 func TestGoGetInsecure(t *testing.T) {

src/cmd/go/pkg.go

@@ -341,19 +341,11 @@ func loadImport(path, srcDir string, parent *Package, stk *importStack, importPo
 		importPath = path
 	}
 
-	if p := packageCache[importPath]; p != nil {
-		if perr := disallowInternal(srcDir, p, stk); perr != p {
-			return perr
-		}
-		if mode&useVendor != 0 {
-			if perr := disallowVendor(srcDir, origPath, p, stk); perr != p {
-				return perr
-			}
-		}
-		return reusePackage(p, stk)
-	}
-
-	p := new(Package)
+	p := packageCache[importPath]
+	if p != nil {
+		p = reusePackage(p, stk)
+	} else {
+		p = new(Package)
 		p.local = isLocal
 		p.ImportPath = importPath
 		packageCache[importPath] = p
@@ -385,6 +377,16 @@ func loadImport(path, srcDir string, parent *Package, stk *importStack, importPo
 			p.Error.Pos = pos.String()
 		}
 
+		if origPath != cleanImport(origPath) {
+			p.Error = &PackageError{
+				ImportStack: stk.copy(),
+				Err:         fmt.Sprintf("non-canonical import path: %q should be %q", origPath, pathpkg.Clean(origPath)),
+			}
+			p.Incomplete = true
+		}
+	}
+
+	// Checked on every import because the rules depend on the code doing the importing.
 	if perr := disallowInternal(srcDir, p, stk); perr != p {
 		return perr
 	}
@@ -394,12 +396,32 @@ func loadImport(path, srcDir string, parent *Package, stk *importStack, importPo
 		}
 	}
 
-	if origPath != cleanImport(origPath) {
-		p.Error = &PackageError{
+	if p.Name == "main" && parent != nil && parent.Dir != p.Dir {
+		perr := *p
+		perr.Error = &PackageError{
 			ImportStack: stk.copy(),
-			Err:         fmt.Sprintf("non-canonical import path: %q should be %q", origPath, pathpkg.Clean(origPath)),
+			Err:         fmt.Sprintf("import %q is a program, not an importable package", path),
 		}
-		p.Incomplete = true
+		if len(importPos) > 0 {
+			pos := importPos[0]
+			pos.Filename = shortPath(pos.Filename)
+			perr.Error.Pos = pos.String()
+		}
+		return &perr
+	}
+
+	if p.local && parent != nil && !parent.local {
+		perr := *p
+		perr.Error = &PackageError{
+			ImportStack: stk.copy(),
+			Err:         fmt.Sprintf("local import %q in non-local package", path),
+		}
+		if len(importPos) > 0 {
+			pos := importPos[0]
+			pos.Filename = shortPath(pos.Filename)
+			perr.Error.Pos = pos.String()
+		}
+		return &perr
 	}
 
 	return p
@@ -445,7 +467,7 @@ func vendoredImportPath(parent *Package, path string) (found string) {
 		root = expandPath(root)
 	}
 
-	if !hasFilePathPrefix(dir, root) || len(dir) <= len(root) || dir[len(root)] != filepath.Separator || parent.ImportPath != "command-line-arguments" && filepath.Join(root, parent.ImportPath) != dir {
+	if !hasFilePathPrefix(dir, root) || len(dir) <= len(root) || dir[len(root)] != filepath.Separator || parent.ImportPath != "command-line-arguments" && !parent.local && filepath.Join(root, parent.ImportPath) != dir {
 		fatalf("unexpected directory layout:\n"+
 			"	import path: %s\n"+
 			"	root: %s\n"+
@@ -974,7 +996,8 @@ func (p *Package) load(stk *importStack, bp *build.Package, err error) *Package
 		// The same import path could produce an error or not,
 		// depending on what tries to import it.
 		// Prefer to record entries with errors, so we can report them.
-		if deps[path] == nil || p1.Error != nil {
+		p0 := deps[path]
+		if p0 == nil || p1.Error != nil && (p0.Error == nil || len(p0.Error.ImportStack) > len(p1.Error.ImportStack)) {
 			deps[path] = p1
 		}
 	}
@@ -984,28 +1007,6 @@ func (p *Package) load(stk *importStack, bp *build.Package, err error) *Package
 			continue
 		}
 		p1 := loadImport(path, p.Dir, p, stk, p.build.ImportPos[path], useVendor)
-		if p1.Name == "main" {
-			p.Error = &PackageError{
-				ImportStack: stk.copy(),
-				Err:         fmt.Sprintf("import %q is a program, not an importable package", path),
-			}
-			pos := p.build.ImportPos[path]
-			if len(pos) > 0 {
-				p.Error.Pos = pos[0].String()
-			}
-		}
-		if p1.local {
-			if !p.local && p.Error == nil {
-				p.Error = &PackageError{
-					ImportStack: stk.copy(),
-					Err:         fmt.Sprintf("local import %q in non-local package", path),
-				}
-				pos := p.build.ImportPos[path]
-				if len(pos) > 0 {
-					p.Error.Pos = pos[0].String()
-				}
-			}
-		}
 		if p.Standard && p.Error == nil && !p1.Standard && p1.Error == nil {
 			p.Error = &PackageError{
 				ImportStack: stk.copy(),

src/cmd/go/testdata/src/importmain/ismain/main.go

@@ -0,0 +1,5 @@
+package main
+
+import _ "importmain/test"
+
+func main() {}

src/cmd/go/testdata/src/importmain/test/test.go

@@ -0,0 +1 @@
+package test

src/cmd/go/testdata/src/importmain/test/test_test.go

@@ -0,0 +1,6 @@
+package test_test
+
+import "testing"
+import _ "importmain/ismain"
+
+func TestCase(t *testing.T) {}