Scott Murphy Heiberg created GROOVY-12688:
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Summary: FormatStringChecker fails inside the compiler on enum and
record declarations
Key: GROOVY-12688
URL: https://issues.apache.org/jira/browse/GROOVY-12688
Project: Groovy
Issue Type: Bug
Affects Versions: 6.0.0
Reporter: Scott Murphy Heiberg
With {{groovy.typecheckers.FormatStringChecker}} enabled, a class that declares
an enum or a record does not compile: the checker throws a
{{NullPointerException}} on a constructor call the compiler generated, and the
compiler reports a general error. The source contains no format call.
{{Size.groovy}} and {{Point.groovy}}:
{code:groovy}
import groovy.transform.TypeChecked
@TypeChecked(extensions = 'groovy.typecheckers.FormatStringChecker')
enum Size { S, M }
{code}
{code:groovy}
import groovy.transform.TypeChecked
@TypeChecked(extensions = 'groovy.typecheckers.FormatStringChecker')
record Point(int x, int y) {}
{code}
{code:sh}
groovyc --check --error-format=short Size.groovy
groovyc --check --error-format=short Point.groovy
{code}
Actual, for each: exit 1 and
{code:text}
org.codehaus.groovy.control.MultipleCompilationErrorsException: startup failed:
error: General error during canonicalization: Cannot get property 'annotations'
on null object
1 error
{code}
With {{groovyc -e --check Size.groovy}}:
{code:text}
java.lang.NullPointerException: Cannot get property 'annotations' on null object
at
org.codehaus.groovy.runtime.NullObject.getProperty(NullObject.java:99)
at
groovy.typecheckers.FormatStringChecker$_run_closure8.doCall(FormatStringChecker.groovy:100)
at groovy.lang.Closure.invokeHandle(Closure.java:647)
at groovy.lang.Closure.invokeCached(Closure.java:618)
at groovy.lang.Closure.call(Closure.java:584)
at
org.codehaus.groovy.transform.stc.AbstractTypeCheckingExtension.safeCall(AbstractTypeCheckingExtension.java:253)
at
org.codehaus.groovy.transform.stc.GroovyTypeCheckingExtensionSupport.afterMethodCall(GroovyTypeCheckingExtensionSupport.java:364)
at
org.codehaus.groovy.transform.stc.DefaultTypeCheckingExtension.afterMethodCall(DefaultTypeCheckingExtension.java:192)
at
org.codehaus.groovy.transform.stc.StaticTypeCheckingVisitor.visitConstructorCallExpression(StaticTypeCheckingVisitor.java:3288)
at
org.codehaus.groovy.ast.expr.ConstructorCallExpression.visit(ConstructorCallExpression.java:74)
at
org.codehaus.groovy.ast.CodeVisitorSupport.visitReturnStatement(CodeVisitorSupport.java:181)
...
{code}
Expected: both compile, as {{@TypeChecked enum PlainEnum { S, M }}} does (exit
0). The same failure appears under static compilation applied by a config
script ({{ast(groovy.transform.CompileStatic, extensions:
['groovy.typecheckers.FormatStringChecker'])}}) to a script containing {{enum
Size { S, M }}} and {{println Size.M}}, and when the enum or record is nested
in a checked class. 6.0.0-beta-1, 5.0.8 and 5.0.0 fail the same way, and so
does current master; this is not a late regression.
Cause: when the type checker cannot resolve a constructor call in generated
code (an enum's synthetic {{$INIT}} delegation, or a record's named-argument
constructor delegation) it drops the error silently and stores no target
method, but still fires {{afterMethodCall}}, where FormatStringChecker reads
{{annotations}} from that null target (line 100). Methods without a body
(abstract or interface methods, or an enum with constant bodies) crash a second
way, {{method.code.visit}} on a null {{code}}, which also affects RegexChecker.
The other checkers in the module guard their target lookups and are not
affected.
A fix that works: return early from {{afterMethodCall}} when the target method
is null, and visit {{method.code}} only when it exists, in FormatStringChecker
and RegexChecker. With it, enums, records, nested declarations and body-less
methods compile cleanly under both checkers, and a genuine format-string
mismatch in such a class is still reported. A pull request with regression
tests in {{FormatStringCheckerTest}} and {{RegexCheckerTest}} follows.
Impact: FormatStringChecker was graduated to stable for 6.0.0 (GROOVY-12039).
Any checked class that declares an enum or record cannot be compiled with it.
Workaround: leave FormatStringChecker off for such sources.
Environment: Groovy 6.0.0 on BellSoft JDK 21.0.12, macOS 26.5 (arm64);
reproduced on master at 9a1a0d0ccb with JDK 21.
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