[nullsafe] Add a test for `switch` case

Summary:
Java treats switch on nullables in a non-obvious way (throws an NPE
surprise) so lets have a decidated test exactly for this.

Reviewed By: ngorogiannis

Differential Revision: D19371280

fbshipit-source-id: d9867b6d6

infer/tests/codetoanalyze/java/nullsafe-default/SwitchCase.java

@@ -0,0 +1,66 @@
+/*
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+package codetoanalyze.java.nullsafe_default;
+
+import javax.annotation.Nullable;
+
+public class SwitchCase {
+  public String switchOnNullIsBad() {
+    Color color = null;
+    switch (color) {
+      case BLACK:
+        return "BLACK";
+      case WHITE:
+        return "WHITE";
+      default:
+        // the default case will never be called.
+        // instead, an NPE will be thrown.
+        return "DEFAULT";
+    }
+  }
+
+  public String switchOnNullableIsBad() {
+    Color color = getNullableColor();
+    switch (color) {
+      case BLACK:
+        return "BLACK";
+      case WHITE:
+        return "WHITE";
+      default:
+        // in case `color` is null, this WON'T BE called.
+        // instead, an NPE will be thrown
+        return "DEFAULT";
+    }
+  }
+
+  public String switchOnNonNullableIsOK() {
+    Color color = getNonNullableColor();
+    switch (color) {
+      case BLACK:
+        return "BLACK";
+      case WHITE:
+        return "WHITE";
+      default:
+        // default case won't happen, but this is fine
+        return "DEFAULT";
+    }
+  }
+
+  private @Nullable Color getNullableColor() {
+    return Color.BLACK;
+  }
+
+  private Color getNonNullableColor() {
+    return Color.BLACK;
+  }
+}
+
+enum Color {
+  BLACK,
+  WHITE;
+}

infer/tests/codetoanalyze/java/nullsafe-default/issues.exp

@@ -243,4 +243,7 @@ codetoanalyze/java/nullsafe-default/StrictModeForThirdParty.java, codetoanalyze.
 codetoanalyze/java/nullsafe-default/StrictModeForThirdParty.java, codetoanalyze.java.nullsafe_default.StrictModeForThirdParty.dereferenceUnspecifiedIsBAD():void, 0, ERADICATE_UNVETTED_THIRD_PARTY_IN_STRICT, no_bucket, WARNING, [`ThirdPartyTestClass.returnUnspecified()`: `@NullsafeStrict` mode prohibits using values coming from not vetted third party methods without a check. Result of this call is used at line 41. Either add a local check for null or assertion, or add the correct signature to nullsafe-default/third-party-signatures/some.test.pckg.sig.]
 codetoanalyze/java/nullsafe-default/StrictModeForThirdParty.java, codetoanalyze.java.nullsafe_default.StrictModeForThirdParty.passingNullableParamToUnspecifiedIsBAD():void, 0, ERADICATE_PARAMETER_NOT_NULLABLE, no_bucket, WARNING, [Third-party `ThirdPartyTestClass.paramUnspecified(...)` is missing a signature that would allow passing a nullable to param #1(`param`). Actual argument `getNullable()` is nullable. Consider adding the correct signature of `ThirdPartyTestClass.paramUnspecified(...)` to nullsafe-default/third-party-signatures/some.test.pckg.sig.]
 codetoanalyze/java/nullsafe-default/StrictModeForThirdParty.java, codetoanalyze.java.nullsafe_default.StrictModeForThirdParty.passingNullableToParamSpecifiedAsNonnullIsBAD():void, 0, ERADICATE_PARAMETER_NOT_NULLABLE, no_bucket, WARNING, [`ThirdPartyTestClass.secondParamSpecifiedAsNonnull(...)`: parameter #2(`specifiedAsNonnull`) is declared non-nullable (see nullsafe-default/third-party-signatures/some.test.pckg.sig at line 3) but the argument `getNullable()` is nullable.]
+codetoanalyze/java/nullsafe-default/SwitchCase.java, codetoanalyze.java.nullsafe_default.SwitchCase.getNullableColor():codetoanalyze.java.nullsafe_default.Color, 0, ERADICATE_RETURN_OVER_ANNOTATED, no_bucket, WARNING, [Method `getNullableColor()` is annotated with `@Nullable` but never returns null.]
+codetoanalyze/java/nullsafe-default/SwitchCase.java, codetoanalyze.java.nullsafe_default.SwitchCase.switchOnNullIsBad():java.lang.String, 1, ERADICATE_NULLABLE_DEREFERENCE, no_bucket, WARNING, [NullPointerException will be thrown at this line! `color` is `null` and is dereferenced via calling `ordinal()`: null constant at line 14]
+codetoanalyze/java/nullsafe-default/SwitchCase.java, codetoanalyze.java.nullsafe_default.SwitchCase.switchOnNullableIsBad():java.lang.String, 1, ERADICATE_NULLABLE_DEREFERENCE, no_bucket, WARNING, [`color` is nullable and is not locally checked for null when calling `ordinal()`: call to getNullableColor() at line 28]
 codetoanalyze/java/nullsafe-default/third-party-test-code/some/test/pckg/ThirdPartyTestClass.java, some.test.pckg.ThirdPartyTestClass.returnSpecifiedAsNullable():java.lang.String, 0, ERADICATE_RETURN_OVER_ANNOTATED, no_bucket, WARNING, [Method `returnSpecifiedAsNullable()` is annotated with `@Nullable` but never returns null.]