Summary:
One limitation of Eradicate is that certain nullability patterns are not expressible using simply the `Nullable` annotation.
One such pattern is using the knowledge that a function returns null when passed null, but returns an object otherwise.
The annotation `PropagatesNullable` is a variant of `Nullable` applied to parameters when their value propagates to the return value.
A method annotated
```
B m(PropagatesNullable A x) { return x == null ? x : B(x); }
```
indicates that `m` returns null if `x` is null, or an object of class `B` if the argument is not null.
Examples with multiple parameters are in the test cases.
This diff builds some infrastructure for annotation transformers: the example above represents the identity function on nullability annotations.
Reviewed By: jvillard
Differential Revision: D4705938
fbshipit-source-id: 9f6194e
master
Cristiano Calcagno
8 years ago
committed by
Facebook Github Bot
parent
69fe80346c
commit
434cfbfb15
@ -0,0 +1,23 @@
|
|||||||
|
/*
|
||||||
|
* Copyright (c) 2017 - present Facebook, Inc.
|
||||||
|
* All rights reserved.
|
||||||
|
*
|
||||||
|
* This source code is licensed under the BSD style license found in the
|
||||||
|
* LICENSE file in the root directory of this source tree. An additional grant
|
||||||
|
* of patent rights can be found in the PATENTS file in the same directory.
|
||||||
|
*/
|
||||||
|
|
||||||
|
package com.facebook.infer.annotation;
|
||||||
|
|
||||||
|
import java.lang.annotation.ElementType;
|
||||||
|
import java.lang.annotation.Retention;
|
||||||
|
import java.lang.annotation.RetentionPolicy;
|
||||||
|
import java.lang.annotation.Target;
|
||||||
|
|
||||||
|
/**
|
||||||
|
* Annotation to indicate that when the parameter is null, the result is also null.
|
||||||
|
*/
|
||||||
|
@Retention(RetentionPolicy.CLASS)
|
||||||
|
@Target({ElementType.PARAMETER})
|
||||||
|
public @interface PropagatesNullable {
|
||||||
|
}
|
||||||
@ -0,0 +1,129 @@
|
|||||||
|
/*
|
||||||
|
* Copyright (c) 2013 - present Facebook, Inc.
|
||||||
|
* All rights reserved.
|
||||||
|
*
|
||||||
|
* This source code is licensed under the BSD style license found in the
|
||||||
|
* LICENSE file in the root directory of this source tree. An additional grant
|
||||||
|
* of patent rights can be found in the PATENTS file in the same directory.
|
||||||
|
*/
|
||||||
|
|
||||||
|
package codetoanalyze.java.eradicate;
|
||||||
|
|
||||||
|
import android.text.TextUtils;
|
||||||
|
|
||||||
|
import javax.annotation.Nullable;
|
||||||
|
import com.facebook.infer.annotation.Assertions;
|
||||||
|
import com.facebook.infer.annotation.FalseOnNull;
|
||||||
|
import com.facebook.infer.annotation.PropagatesNullable;
|
||||||
|
import com.facebook.infer.annotation.TrueOnNull;
|
||||||
|
|
||||||
|
|
||||||
|
public class CustomAnnotations {
|
||||||
|
|
||||||
|
static class MyTextUtils {
|
||||||
|
|
||||||
|
@TrueOnNull
|
||||||
|
static boolean isEmpty(@Nullable java.lang.CharSequence s) {
|
||||||
|
return s == null || s.equals("");
|
||||||
|
}
|
||||||
|
|
||||||
|
@FalseOnNull
|
||||||
|
static boolean isNotEmpty(@Nullable java.lang.CharSequence s) {
|
||||||
|
return s != null && s.length() > 0;
|
||||||
|
}
|
||||||
|
}
|
||||||
|
|
||||||
|
class TestTextUtilsIsEmpty {
|
||||||
|
void textUtilsNotIsEmpty(@Nullable CharSequence s) {
|
||||||
|
if (!TextUtils.isEmpty(s)) {
|
||||||
|
s.toString(); // OK
|
||||||
|
}
|
||||||
|
}
|
||||||
|
|
||||||
|
void textUtilsIsEmpty(@Nullable CharSequence s) {
|
||||||
|
if (TextUtils.isEmpty(s)) {
|
||||||
|
s.toString(); // BAD
|
||||||
|
}
|
||||||
|
}
|
||||||
|
|
||||||
|
void myTextUtilsNotIsEmpty(@Nullable CharSequence s) {
|
||||||
|
if (!MyTextUtils.isEmpty(s)) {
|
||||||
|
s.toString(); // OK
|
||||||
|
}
|
||||||
|
}
|
||||||
|
|
||||||
|
void myTextUtilsIsEmpty(@Nullable CharSequence s) {
|
||||||
|
if (MyTextUtils.isEmpty(s)) {
|
||||||
|
s.toString(); // BAD
|
||||||
|
}
|
||||||
|
}
|
||||||
|
void myTextUtilsIsNotEmpty(@Nullable CharSequence s) {
|
||||||
|
if (MyTextUtils.isNotEmpty(s)) {
|
||||||
|
s.toString(); // OK
|
||||||
|
}
|
||||||
|
}
|
||||||
|
|
||||||
|
void myTextUtilsNotIsNotEmpty(@Nullable CharSequence s) {
|
||||||
|
if (!MyTextUtils.isNotEmpty(s)) {
|
||||||
|
s.toString(); // BAD
|
||||||
|
}
|
||||||
|
}
|
||||||
|
}
|
||||||
|
|
||||||
|
|
||||||
|
// Tests for the annotation @PropagatesNullable
|
||||||
|
class TestPropagatesNullable {
|
||||||
|
|
||||||
|
// one parameter: means return null iff s is null
|
||||||
|
String m(@PropagatesNullable String s) {
|
||||||
|
return s;
|
||||||
|
}
|
||||||
|
|
||||||
|
void mBad() {
|
||||||
|
m(null).length(); // bad: m returns null
|
||||||
|
}
|
||||||
|
|
||||||
|
void mGood() {
|
||||||
|
m("").length();
|
||||||
|
}
|
||||||
|
|
||||||
|
// limitation: we currently cannot check the body, and just trust the annotation
|
||||||
|
String cannotCheckBody(@PropagatesNullable String s) {
|
||||||
|
return null; // nothing is reported here
|
||||||
|
}
|
||||||
|
|
||||||
|
void illustrateFalseNegativeAsCannotCheckBody() {
|
||||||
|
cannotCheckBody("").length(); // this is an NPE but is not found
|
||||||
|
}
|
||||||
|
|
||||||
|
// second parameter: means return null iff s2 is null
|
||||||
|
String m2(@Nullable String s1, @PropagatesNullable String s2) {
|
||||||
|
return s2;
|
||||||
|
}
|
||||||
|
|
||||||
|
void m2Bad() {
|
||||||
|
m2(null, null).length(); // bad: m2 returns null
|
||||||
|
}
|
||||||
|
|
||||||
|
void m2Good() {
|
||||||
|
m2(null, "").length();
|
||||||
|
}
|
||||||
|
|
||||||
|
// two parameters: means return null iff either s1 or s2 is null
|
||||||
|
String m12(@PropagatesNullable String s1, @PropagatesNullable String s2) {
|
||||||
|
return s1 == null ? s1 : s2;
|
||||||
|
}
|
||||||
|
|
||||||
|
void m12Bad1() {
|
||||||
|
m12(null, "").length(); // bad: m12 returns null
|
||||||
|
}
|
||||||
|
|
||||||
|
void m12Bad2() {
|
||||||
|
m12("", null).length(); // bad: m12 returns null
|
||||||
|
}
|
||||||
|
|
||||||
|
void m12Good() {
|
||||||
|
m12("", "").length();
|
||||||
|
}
|
||||||
|
}
|
||||||
|
}
|
||||||
Loading…
Reference in new issue