Merge "Guide behavior changes towards CompatChanges."

2 files changed, 119 insertions, 5 deletions

diff --git a/errorprone/java/com/google/errorprone/bugpatterns/android/CompatChangeChecker.java b/errorprone/java/com/google/errorprone/bugpatterns/android/CompatChangeChecker.java
new file mode 100644
index 000000000000..8829b0d3c649
--- /dev/null
+++ b/errorprone/java/com/google/errorprone/bugpatterns/android/CompatChangeChecker.java
@@ -0,0 +1,109 @@
+/*
+ * Copyright (C) 2020 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.google.errorprone.bugpatterns.android;
+
+import static com.google.errorprone.BugPattern.SeverityLevel.WARNING;
+import static com.google.errorprone.matchers.FieldMatchers.anyFieldInClass;
+import static com.google.errorprone.matchers.FieldMatchers.staticField;
+import static com.google.errorprone.matchers.Matchers.allOf;
+import static com.google.errorprone.matchers.Matchers.anyOf;
+import static com.google.errorprone.matchers.Matchers.anything;
+import static com.google.errorprone.matchers.Matchers.binaryTree;
+import static com.google.errorprone.matchers.Matchers.not;
+
+import com.google.auto.service.AutoService;
+import com.google.errorprone.BugPattern;
+import com.google.errorprone.VisitorState;
+import com.google.errorprone.bugpatterns.BugChecker;
+import com.google.errorprone.bugpatterns.BugChecker.BinaryTreeMatcher;
+import com.google.errorprone.matchers.Description;
+import com.google.errorprone.matchers.Matcher;
+import com.sun.source.tree.BinaryTree;
+import com.sun.source.tree.ExpressionTree;
+
+/**
+ * Each SDK level often has dozens of different behavior changes, which can be
+ * difficult for large app developers to adjust to during preview or beta
+ * releases. For this reason, {@code android.app.compat.CompatChanges} was
+ * introduced as a new best-practice for adding behavior changes.
+ * <p>
+ * During a preview or beta release, developers can temporarily opt-out of each
+ * individual change to aid debugging. This opt-out is only available during
+ * preview of beta releases, and cannot be adjusted on finalized builds.
+ */
+@AutoService(BugChecker.class)
+@BugPattern(
+    name = "AndroidFrameworkCompatChange",
+    summary = "Verifies that behavior changes use the modern compatibility framework",
+    severity = WARNING)
+public final class CompatChangeChecker extends BugChecker implements BinaryTreeMatcher {
+    private static final Matcher<ExpressionTree> VERSION_CODE =
+            anyFieldInClass("android.os.Build.VERSION_CODES");
+
+    // Ship has already sailed on these SDK levels; not worth fixing
+    private static final Matcher<ExpressionTree> LEGACY_VERSION_CODE = anyOf(
+            staticField("android.os.Build.VERSION_CODES", "BASE"),
+            staticField("android.os.Build.VERSION_CODES", "BASE_1_1"),
+            staticField("android.os.Build.VERSION_CODES", "CUPCAKE"),
+            staticField("android.os.Build.VERSION_CODES", "DONUT"),
+            staticField("android.os.Build.VERSION_CODES", "ECLAIR"),
+            staticField("android.os.Build.VERSION_CODES", "ECLAIR_0_1"),
+            staticField("android.os.Build.VERSION_CODES", "ECLAIR_MR1"),
+            staticField("android.os.Build.VERSION_CODES", "FROYO"),
+            staticField("android.os.Build.VERSION_CODES", "GINGERBREAD"),
+            staticField("android.os.Build.VERSION_CODES", "GINGERBREAD_MR1"),
+            staticField("android.os.Build.VERSION_CODES", "HONEYCOMB"),
+            staticField("android.os.Build.VERSION_CODES", "HONEYCOMB_MR1"),
+            staticField("android.os.Build.VERSION_CODES", "HONEYCOMB_MR2"),
+            staticField("android.os.Build.VERSION_CODES", "ICE_CREAM_SANDWICH"),
+            staticField("android.os.Build.VERSION_CODES", "ICE_CREAM_SANDWICH_MR1"),
+            staticField("android.os.Build.VERSION_CODES", "JELLY_BEAN"),
+            staticField("android.os.Build.VERSION_CODES", "JELLY_BEAN_MR1"),
+            staticField("android.os.Build.VERSION_CODES", "JELLY_BEAN_MR2"),
+            staticField("android.os.Build.VERSION_CODES", "KITKAT"),
+            staticField("android.os.Build.VERSION_CODES", "KITKAT_WATCH"),
+            staticField("android.os.Build.VERSION_CODES", "L"),
+            staticField("android.os.Build.VERSION_CODES", "LOLLIPOP"),
+            staticField("android.os.Build.VERSION_CODES", "LOLLIPOP_MR1"),
+            staticField("android.os.Build.VERSION_CODES", "M"),
+            staticField("android.os.Build.VERSION_CODES", "N"),
+            staticField("android.os.Build.VERSION_CODES", "N_MR1"),
+            staticField("android.os.Build.VERSION_CODES", "O"),
+            staticField("android.os.Build.VERSION_CODES", "O_MR1"),
+            staticField("android.os.Build.VERSION_CODES", "P"),
+            staticField("android.os.Build.VERSION_CODES", "Q"));
+
+    private static final Matcher<ExpressionTree> MODERN_VERSION_CODE =
+            allOf(VERSION_CODE, not(LEGACY_VERSION_CODE));
+
+    private static final Matcher<BinaryTree> INVALID = anyOf(
+            binaryTree(MODERN_VERSION_CODE, anything()),
+            binaryTree(anything(), MODERN_VERSION_CODE));
+
+    @Override
+    public Description matchBinary(BinaryTree tree, VisitorState state) {
+        if (INVALID.matches(tree, state)) {
+            return buildDescription(tree)
+                    .setMessage("Behavior changes should use CompatChanges.isChangeEnabled() "
+                            + "instead of direct SDK checks to ease developer transitions; "
+                            + "see go/compat-framework for more details")
+                    .build();
+
+        }
+        return Description.NO_MATCH;
+    }
+}
diff --git a/errorprone/java/com/google/errorprone/matchers/FieldMatchers.java b/errorprone/java/com/google/errorprone/matchers/FieldMatchers.java
index 46f0fb2e534c..08969d60671a 100644
--- a/errorprone/java/com/google/errorprone/matchers/FieldMatchers.java
+++ b/errorprone/java/com/google/errorprone/matchers/FieldMatchers.java
@@ -36,7 +36,8 @@ public final class FieldMatchers {
     return new FieldReferenceMatcher() {
       @Override
       boolean classIsAppropriate(ClassSymbol classSymbol) {
-        return classSymbol.getQualifiedName().contentEquals(className);
+        return classSymbol != null
+                && classSymbol.getQualifiedName().contentEquals(className);
       }
 
       @Override
@@ -50,12 +51,14 @@ public final class FieldMatchers {
     return new FieldReferenceMatcher() {
       @Override
       boolean classIsAppropriate(ClassSymbol classSymbol) {
-        return classSymbol.getQualifiedName().contentEquals(className);
+        return classSymbol != null
+                && classSymbol.getQualifiedName().contentEquals(className);
       }
 
       @Override
       boolean fieldSymbolIsAppropriate(Symbol symbol) {
-        return symbol.isStatic() && symbol.getSimpleName().contentEquals(fieldName);
+        return symbol != null
+                && symbol.isStatic() && symbol.getSimpleName().contentEquals(fieldName);
       }
     };
   }
@@ -64,12 +67,14 @@ public final class FieldMatchers {
     return new FieldReferenceMatcher() {
       @Override
       boolean classIsAppropriate(ClassSymbol classSymbol) {
-        return classSymbol.getQualifiedName().contentEquals(className);
+        return classSymbol != null
+                && classSymbol.getQualifiedName().contentEquals(className);
       }
 
       @Override
       boolean fieldSymbolIsAppropriate(Symbol symbol) {
-        return !symbol.isStatic() && symbol.getSimpleName().contentEquals(fieldName);
+        return symbol != null
+                && !symbol.isStatic() && symbol.getSimpleName().contentEquals(fieldName);
       }
     };
   }