Preserve aliased imports when parsing embedded interface packages

mockgen/internal/tests/aliased_embedded_interface/source.go

@@ -0,0 +1,7 @@
+package aliased_embedded_interface
+
+import "go.uber.org/mock/mockgen/internal/tests/aliased_embedded_interface/subpkg"
+
+type Embedder interface {
+	subpkg.Embedded
+}

mockgen/internal/tests/aliased_embedded_interface/subpkg/a_plain.go

@@ -0,0 +1,5 @@
+package subpkg
+
+import "time"
+
+var _ = time.Time{}

mockgen/internal/tests/aliased_embedded_interface/subpkg/b_aliased.go

@@ -0,0 +1,10 @@
+package subpkg
+
+import aliased_time_import "time"
+
+// Embedded is embedded by an interface in the parent package. Its method
+// references time.Time through an aliased import that lives only in this
+// (alphabetically later) file. See uber-go/mock#254.
+type Embedded interface {
+	Foo(t aliased_time_import.Time)
+}

mockgen/parse.go

@@ -299,9 +299,15 @@ func (p *fileParser) parsePackage(path string) (*fileParser, error) {
 		for ni := range iterInterfaces(file) {
 			newP.importedInterfaces.Set(path, ni.name.Name, ni)
 		}
-		imports, _ := importsOfFile(file)
-		for pkgName, pkgI := range imports {
-			newP.imports[pkgName] = pkgI
+		// Collect imports from each file rather than the merged file:
+		// FilterImportDuplicates dedupes imports by path, which drops an alias
+		// that only appears in one file and makes it look like an unknown
+		// package during type resolution (#254).
+		for _, f := range pkg.Files {
+			imports, _ := importsOfFile(f)
+			for pkgName, pkgI := range imports {
+				newP.imports[pkgName] = pkgI
+			}
 		}
 	}
 	return newP, nil

mockgen/parse_test.go

@@ -107,6 +107,17 @@ func checkGreeterImports(t *testing.T, imports map[string]importedPackage) {
 	}
 }
 
+func TestParseSourceWithAliasedImportInEmbeddedInterfacePackage(t *testing.T) {
+	// Regression test for #254. Source mode must resolve an embedded interface
+	// whose package aliases an import in an alphabetically-later file. Merging
+	// the package's files drops the alias, so parsing used to fail with
+	// `unknown package`.
+	_, err := sourceMode("internal/tests/aliased_embedded_interface/source.go")
+	if err != nil {
+		t.Fatalf("Unexpected error: %v", err)
+	}
+}
+
 func Benchmark_parseFile(b *testing.B) {
 	source := "internal/tests/performance/big_interface/big_interface.go"
 	for n := 0; n < b.N; n++ {