Connecting up the augmentor

Author: grantnelson-wf

compiler/astutil/astutil.go

@@ -531,8 +531,16 @@ func ConcatenateFiles(file *ast.File, tails ...*ast.File) error {
 			path := imp.Path.Value
 			if oldImp, ok := imports[path]; ok {
 				// Import is in both files so check if the import name is not different.
-				if oldName, newName := ImportName(oldImp), ImportName(imp); oldName != newName {
-					return fmt.Errorf("import from of %s can not be concatenated with different name: %q != %q", path, oldName, newName)
+				oldName, newName := ImportName(oldImp), ImportName(imp)
+				if oldName != newName {
+					if len(oldName) == 0 {
+						// Update the import name to the new name.
+						// This assumes the import name was `_` and
+						// could cause problems if it was `.`
+						oldImp.Name = imp.Name
+					} else if len(newName) != 0 {
+						return fmt.Errorf("import from of %s can not be concatenated with different name: %q != %q", path, oldName, newName)
+					}
 				}
 				continue
 			}

compiler/astutil/astutil_test.go

@@ -1076,6 +1076,34 @@ func TestConcatenateFiles(t *testing.T) {
 					import f2 "fmt"
 					func bar() { f2.Println("bar") }`,
 			expErr: `import from of "fmt" can not be concatenated with different name: "f1" != "f2"`,
+		}, {
+			name: `import mismatch with old being blank`,
+			srcHead: `package testpackage
+					import _ "unsafe"
+					//go:linkname foo runtime.foo
+					func bar()`,
+			srcTail: `package testpackage
+					import "unsafe"
+					func foo() unsafe.Pointer { return nil }`,
+			want: `package testpackage
+					import "unsafe"
+					//go:linkname foo runtime.foo
+					func bar()
+					func foo() unsafe.Pointer { return nil }`,
+		}, {
+			name: `import mismatch with new being blank`,
+			srcHead: `package testpackage
+					import "unsafe"
+					func foo() unsafe.Pointer { return nil }`,
+			srcTail: `package testpackage
+					import _ "unsafe"
+					//go:linkname foo runtime.foo
+					func bar()`,
+			want: `package testpackage
+					import "unsafe"
+					func foo() unsafe.Pointer { return nil }
+					//go:linkname foo runtime.foo
+					func bar()`,
 		},
 	}