imports: ignore globals in different packages

Some people put multiple packages' files in the same directory, most
commonly commands and code generators. Global variables from one package
should be ignored in other packages.

Change-Id: I9a5d27778570183dfe391dd3273dfa8277a29bf2
Reviewed-on: https://go-review.googlesource.com/c/153419
Run-TryBot: Heschi Kreinick <heschi@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

imports/fix.go

@@ -282,7 +282,11 @@ func (p *pass) load() bool {
 	// that we might want to mimic.
 	globals := map[string]bool{}
 	for _, otherFile := range p.otherFiles {
-		addGlobals(otherFile, globals)
+		// Don't load globals from files that are in the same directory
+		// but a different package. Using them to suggest imports is OK.
+		if p.f.Name.Name == otherFile.Name.Name {
+			addGlobals(otherFile, globals)
+		}
 		p.candidates = append(p.candidates, collectImports(otherFile)...)
 	}
 

imports/fix_test.go

@@ -1882,6 +1882,33 @@ var time Time
 	}.processTest(t, "foo.com", "pkg/uses.go", nil, nil, usesGlobal)
 }
 
+// Some people put multiple packages' files in the same directory. Globals
+// declared in other packages should be ignored.
+func TestGlobalImports_DifferentPackage(t *testing.T) {
+	const declaresGlobal = `package main
+var fmt int
+`
+	const input = `package pkg
+var _ = fmt.Printf
+`
+	const want = `package pkg
+
+import "fmt"
+
+var _ = fmt.Printf
+`
+
+	testConfig{
+		module: packagestest.Module{
+			Name: "foo.com",
+			Files: fm{
+				"pkg/main.go": declaresGlobal,
+				"pkg/uses.go": input,
+			},
+		},
+	}.processTest(t, "foo.com", "pkg/uses.go", nil, nil, want)
+}
+
 // Tests that sibling files - other files in the same package - can provide an
 // import that may not be the default one otherwise.
 func TestSiblingImports(t *testing.T) {