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Prevent NestedOptionals from throwing an NPE #412

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Dec 16, 2022
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Prevent NestedOptionals from throwing an NPE #412

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8f83c82
fix: NPE thrown in NestedOptionals
gtoison Dec 14, 2022
27e28e2
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Stephan202 Dec 14, 2022
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9 changes: 6 additions & 3 deletions error-prone-contrib/src/main/java/tech/picnic/errorprone/bugpatterns/NestedOptionals.java
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Original file line number Diff line number Diff line change
Expand Up @@ -41,8 +41,11 @@ public NestedOptionals() {}

@Override
public Description matchMethodInvocation(MethodInvocationTree tree, VisitorState state) {
return state.getTypes().isSubtype(ASTHelpers.getType(tree), OPTIONAL_OF_OPTIONAL.get(state))
? describeMatch(tree)
: Description.NO_MATCH;
Type stateType = OPTIONAL_OF_OPTIONAL.get(state);
if (stateType != null && state.getTypes().isSubtype(ASTHelpers.getType(tree), stateType)) {
return describeMatch(tree);
} else {
return Description.NO_MATCH;
}
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Alright, so I guess that the issue happens if the Optional class isn't loaded during compilation at all. That realization also lead to this code.

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We do have a preference for an early return with Description.NO_MATCH:

Suggested change
Type stateType = OPTIONAL_OF_OPTIONAL.get(state);
if (stateType != null && state.getTypes().isSubtype(ASTHelpers.getType(tree), stateType)) {
return describeMatch(tree);
} else {
return Description.NO_MATCH;
}
Type type = OPTIONAL_OF_OPTIONAL.get(state);
if (type == null || !state.getTypes().isSubtype(ASTHelpers.getType(tree), type)) {
return Description.NO_MATCH;
}
return describeMatch(tree);

}
}
15 changes: 15 additions & 0 deletions ...r-prone-contrib/src/test/java/tech/picnic/errorprone/bugpatterns/NestedOptionalsTest.java
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Expand Up @@ -39,4 +39,19 @@ void identification() {
"}")
.doTest();
}

@Test
void failingTypeCheck() {
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Slightly more in line which what we do in a few other places

Suggested change
void failingTypeCheck() {
void identificationOptionalTypeNotLoaded() {

(Funny: I tried to replace the Duration expression below with Stream.empty(), but then the NPE didn't happen. I think because Stream does reference Optional, while Duration (and ChronoUnit) don't.

compilationTestHelper
.addSourceLines(
"B.java",
"import java.time.temporal.ChronoUnit;",
"",
"class B {",
" void m() {",
" java.time.Duration.of(1, ChronoUnit.YEARS);",
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I suggest using a slightly more realistic case ;)

jshell> java.time.Duration.of(1, java.time.temporal.ChronoUnit.YEARS)
|  Exception java.time.temporal.UnsupportedTemporalTypeException: Unit must not have an estimated duration
|        at Duration.plus (Duration.java:717)
|        at Duration.of (Duration.java:312)
|        at (#1:1)

" }",
"}")
.doTest();
}
}