Psalm config for detecting unsafe array access when migrating PHP7 - 8

psalm-php8-migration.xml

<?xml version="1.0"?>
<psalm
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns="https://getpsalm.org/schema/config"
    xsi:schemaLocation="https://getpsalm.org/schema/config vendor/vimeo/psalm/config.xsd"
    errorLevel="1"
    phpVersion="8.0"

    ensureArrayStringOffsetsExist="true"
    ensureArrayIntOffsetsExist="true"
>

    <projectFiles>
        <directory name="src"/>
        <ignoreFiles>
            <directory name="vendor"/>
        </ignoreFiles>
    </projectFiles>

    <issueHandlers>
        <AbstractInstantiation errorLevel="suppress"/>
        <AbstractMethodCall errorLevel="suppress"/>
        <ArgumentTypeCoercion errorLevel="suppress"/>
        <AssignmentToVoid errorLevel="suppress"/>
        <CircularReference errorLevel="suppress"/>
        <ComplexFunction errorLevel="suppress"/>
        <ComplexMethod errorLevel="suppress"/>
        <ConfigIssue errorLevel="suppress"/>
        <ConflictingReferenceConstraint errorLevel="suppress"/>
        <ConstructorSignatureMismatch errorLevel="suppress"/>
        <ContinueOutsideLoop errorLevel="suppress"/>
        <DeprecatedClass errorLevel="suppress"/>
        <DeprecatedConstant errorLevel="suppress"/>
        <DeprecatedFunction errorLevel="suppress"/>
        <DeprecatedInterface errorLevel="suppress"/>
        <DeprecatedMethod errorLevel="suppress"/>
        <DeprecatedProperty errorLevel="suppress"/>
        <DeprecatedTrait errorLevel="suppress"/>
        <DocblockTypeContradiction errorLevel="suppress"/>
        <DuplicateArrayKey errorLevel="suppress"/>
        <DuplicateClass errorLevel="suppress"/>
        <DuplicateConstant errorLevel="suppress"/>
        <DuplicateEnumCase errorLevel="suppress"/>
        <DuplicateEnumCaseValue errorLevel="suppress"/>
        <DuplicateFunction errorLevel="suppress"/>
        <DuplicateMethod errorLevel="suppress"/>
        <DuplicateParam errorLevel="suppress"/>
        <EmptyArrayAccess errorLevel="suppress"/>
        <ExtensionRequirementViolation errorLevel="suppress"/>
        <FalsableReturnStatement errorLevel="suppress"/>
        <FalseOperand errorLevel="suppress"/>
        <ForbiddenCode errorLevel="suppress"/>
        <ForbiddenEcho errorLevel="suppress"/>
        <IfThisIsMismatch errorLevel="suppress"/>
        <ImplementationRequirementViolation errorLevel="suppress"/>
        <ImplementedParamTypeMismatch errorLevel="suppress"/>
        <ImplementedReturnTypeMismatch errorLevel="suppress"/>
        <ImplicitToStringCast errorLevel="suppress"/>
        <ImpureByReferenceAssignment errorLevel="suppress"/>
        <ImpureFunctionCall errorLevel="suppress"/>
        <ImpureMethodCall errorLevel="suppress"/>
        <ImpurePropertyAssignment errorLevel="suppress"/>
        <ImpurePropertyFetch errorLevel="suppress"/>
        <ImpureStaticProperty errorLevel="suppress"/>
        <ImpureStaticVariable errorLevel="suppress"/>
        <ImpureVariable errorLevel="suppress"/>
        <InaccessibleClassConstant errorLevel="suppress"/>
        <InaccessibleMethod errorLevel="suppress"/>
        <InaccessibleProperty errorLevel="suppress"/>
        <InterfaceInstantiation errorLevel="suppress"/>
        <InternalClass errorLevel="suppress"/>
        <InternalMethod errorLevel="suppress"/>
        <InternalProperty errorLevel="suppress"/>
        <InvalidArgument errorLevel="suppress"/>
<!--        <InvalidArrayAccess errorLevel="suppress"/>-->
        <InvalidArrayAssignment errorLevel="suppress"/>
        <InvalidArrayOffset errorLevel="suppress"/>
        <InvalidAttribute errorLevel="suppress"/>
        <InvalidCast errorLevel="suppress"/>
        <InvalidCatch errorLevel="suppress"/>
        <InvalidClass errorLevel="suppress"/>
        <InvalidClone errorLevel="suppress"/>
        <InvalidDocblock errorLevel="suppress"/>
        <InvalidDocblockParamName errorLevel="suppress"/>
        <InvalidEnumBackingType errorLevel="suppress"/>
        <InvalidEnumCaseValue errorLevel="suppress"/>
        <InvalidExtendClass errorLevel="suppress"/>
        <InvalidFalsableReturnType errorLevel="suppress"/>
        <InvalidFunctionCall errorLevel="suppress"/>
        <InvalidGlobal errorLevel="suppress"/>
        <InvalidIterator errorLevel="suppress"/>
        <InvalidLiteralArgument errorLevel="suppress"/>
        <InvalidMethodCall errorLevel="suppress"/>
        <InvalidNamedArgument errorLevel="suppress"/>
        <InvalidNullableReturnType errorLevel="suppress"/>
        <InvalidOperand errorLevel="suppress"/>
        <InvalidParamDefault errorLevel="suppress"/>
        <InvalidParent errorLevel="suppress"/>
        <InvalidPassByReference errorLevel="suppress"/>
        <InvalidPropertyAssignment errorLevel="suppress"/>
        <InvalidPropertyAssignmentValue errorLevel="suppress"/>
        <InvalidPropertyFetch errorLevel="suppress"/>
        <InvalidReturnStatement errorLevel="suppress"/>
        <InvalidReturnType errorLevel="suppress"/>
        <InvalidScalarArgument errorLevel="suppress"/>
        <InvalidScope errorLevel="suppress"/>
        <InvalidStaticInvocation errorLevel="suppress"/>
        <InvalidStringClass errorLevel="suppress"/>
        <InvalidTemplateParam errorLevel="suppress"/>
        <InvalidThrow errorLevel="suppress"/>
        <InvalidToString errorLevel="suppress"/>
        <InvalidTraversableImplementation errorLevel="suppress"/>
        <InvalidTypeImport errorLevel="suppress"/>
        <LessSpecificImplementedReturnType errorLevel="suppress"/>
        <LessSpecificReturnStatement errorLevel="suppress"/>
        <LessSpecificReturnType errorLevel="suppress"/>
        <LoopInvalidation errorLevel="suppress"/>
        <MethodSignatureMismatch errorLevel="suppress"/>
        <MethodSignatureMustOmitReturnType errorLevel="suppress"/>
        <MethodSignatureMustProvideReturnType errorLevel="suppress"/>
        <MismatchingDocblockParamType errorLevel="suppress"/>
        <MismatchingDocblockPropertyType errorLevel="suppress"/>
        <MismatchingDocblockReturnType errorLevel="suppress"/>
        <MissingClosureParamType errorLevel="suppress"/>
        <MissingClosureReturnType errorLevel="suppress"/>
        <MissingConstructor errorLevel="suppress"/>
        <MissingDependency errorLevel="suppress"/>
        <MissingDocblockType errorLevel="suppress"/>
        <MissingFile errorLevel="suppress"/>
        <MissingImmutableAnnotation errorLevel="suppress"/>
        <MissingParamType errorLevel="suppress"/>
        <MissingPropertyType errorLevel="suppress"/>
        <MissingReturnType errorLevel="suppress"/>
        <MissingTemplateParam errorLevel="suppress"/>
        <MissingThrowsDocblock errorLevel="suppress"/>
        <MixedArgument errorLevel="suppress"/>
        <MixedArgumentTypeCoercion errorLevel="suppress"/>
        <MixedArrayAccess errorLevel="suppress"/>
        <MixedArrayAssignment errorLevel="suppress"/>
        <MixedArrayOffset errorLevel="suppress"/>
        <MixedArrayTypeCoercion errorLevel="suppress"/>
        <MixedAssignment errorLevel="suppress"/>
        <MixedClone errorLevel="suppress"/>
        <MixedFunctionCall errorLevel="suppress"/>
        <MixedInferredReturnType errorLevel="suppress"/>
        <MixedMethodCall errorLevel="suppress"/>
        <MixedOperand errorLevel="suppress"/>
        <MixedPropertyAssignment errorLevel="suppress"/>
        <MixedPropertyFetch errorLevel="suppress"/>
        <MixedPropertyTypeCoercion errorLevel="suppress"/>
        <MixedReturnStatement errorLevel="suppress"/>
        <MixedReturnTypeCoercion errorLevel="suppress"/>
        <MixedStringOffsetAssignment errorLevel="suppress"/>
        <MoreSpecificImplementedParamType errorLevel="suppress"/>
        <MoreSpecificReturnType errorLevel="suppress"/>
        <MutableDependency errorLevel="suppress"/>
        <NamedArgumentNotAllowed errorLevel="suppress"/>
        <NoEnumProperties errorLevel="suppress"/>
        <NoInterfaceProperties errorLevel="suppress"/>
        <NoValue errorLevel="suppress"/>
        <NonInvariantDocblockPropertyType errorLevel="suppress"/>
        <NonInvariantPropertyType errorLevel="suppress"/>
        <NonStaticSelfCall errorLevel="suppress"/>
        <NullArgument errorLevel="suppress"/>
<!--        <NullArrayAccess errorLevel="suppress"/>-->
        <NullArrayOffset errorLevel="suppress"/>
        <NullFunctionCall errorLevel="suppress"/>
        <NullIterator errorLevel="suppress"/>
        <NullOperand errorLevel="suppress"/>
        <NullPropertyAssignment errorLevel="suppress"/>
        <NullPropertyFetch errorLevel="suppress"/>
        <NullReference errorLevel="suppress"/>
        <NullableReturnStatement errorLevel="suppress"/>
        <OverriddenMethodAccess errorLevel="suppress"/>
        <OverriddenPropertyAccess errorLevel="suppress"/>
        <ParadoxicalCondition errorLevel="suppress"/>
        <ParamNameMismatch errorLevel="suppress"/>
        <ParentNotFound errorLevel="suppress"/>
        <PossibleRawObjectIteration errorLevel="suppress"/>
        <PossiblyFalseArgument errorLevel="suppress"/>
        <PossiblyFalseIterator errorLevel="suppress"/>
        <PossiblyFalseOperand errorLevel="suppress"/>
        <PossiblyFalsePropertyAssignmentValue errorLevel="suppress"/>
        <PossiblyFalseReference errorLevel="suppress"/>
        <PossiblyInvalidArgument errorLevel="suppress"/>
        <PossiblyInvalidArrayAccess errorLevel="suppress"/>
        <PossiblyInvalidArrayAssignment errorLevel="suppress"/>
<!--        <PossiblyInvalidArrayOffset errorLevel="suppress"/>-->
        <PossiblyInvalidCast errorLevel="suppress"/>
        <PossiblyInvalidClone errorLevel="suppress"/>
        <PossiblyInvalidDocblockTag errorLevel="suppress"/>
        <PossiblyInvalidFunctionCall errorLevel="suppress"/>
        <PossiblyInvalidIterator errorLevel="suppress"/>
        <PossiblyInvalidMethodCall errorLevel="suppress"/>
        <PossiblyInvalidOperand errorLevel="suppress"/>
        <PossiblyInvalidPropertyAssignment errorLevel="suppress"/>
        <PossiblyInvalidPropertyAssignmentValue errorLevel="suppress"/>
        <PossiblyInvalidPropertyFetch errorLevel="suppress"/>
        <PossiblyNullArgument errorLevel="suppress"/>
<!--        <PossiblyNullArrayAccess errorLevel="suppress"/>-->
        <PossiblyNullArrayAssignment errorLevel="suppress"/>
        <PossiblyNullArrayOffset errorLevel="suppress"/>
        <PossiblyNullFunctionCall errorLevel="suppress"/>
        <PossiblyNullIterator errorLevel="suppress"/>
        <PossiblyNullOperand errorLevel="suppress"/>
        <PossiblyNullPropertyAssignment errorLevel="suppress"/>
        <PossiblyNullPropertyAssignmentValue errorLevel="suppress"/>
        <PossiblyNullPropertyFetch errorLevel="suppress"/>
        <PossiblyNullReference errorLevel="suppress"/>
<!--        <PossiblyUndefinedArrayOffset errorLevel="suppress"/>-->
        <PossiblyUndefinedGlobalVariable errorLevel="suppress"/>
<!--        <PossiblyUndefinedIntArrayOffset errorLevel="suppress"/>-->
        <PossiblyUndefinedMethod errorLevel="suppress"/>
<!--        <PossiblyUndefinedStringArrayOffset errorLevel="suppress"/>-->
        <PossiblyUndefinedVariable errorLevel="suppress"/>
        <PossiblyUnusedMethod errorLevel="suppress"/>
        <PossiblyUnusedParam errorLevel="suppress"/>
        <PossiblyUnusedProperty errorLevel="suppress"/>
        <PossiblyUnusedReturnValue errorLevel="suppress"/>
        <PropertyNotSetInConstructor errorLevel="suppress"/>
        <PropertyTypeCoercion errorLevel="suppress"/>
        <RawObjectIteration errorLevel="suppress"/>
        <RedundantCast errorLevel="suppress"/>
        <RedundantCastGivenDocblockType errorLevel="suppress"/>
        <RedundantCondition errorLevel="suppress"/>
        <RedundantConditionGivenDocblockType errorLevel="suppress"/>
        <RedundantFunctionCall errorLevel="suppress"/>
        <RedundantFunctionCallGivenDocblockType errorLevel="suppress"/>
        <RedundantIdentityWithTrue errorLevel="suppress"/>
        <RedundantPropertyInitializationCheck errorLevel="suppress"/>
        <ReferenceConstraintViolation errorLevel="suppress"/>
        <ReservedWord errorLevel="suppress"/>
        <StringIncrement errorLevel="suppress"/>
        <TaintedCallable errorLevel="suppress"/>
        <TaintedCookie errorLevel="suppress"/>
        <TaintedCustom errorLevel="suppress"/>
        <TaintedEval errorLevel="suppress"/>
        <TaintedFile errorLevel="suppress"/>
        <TaintedHeader errorLevel="suppress"/>
        <TaintedHtml errorLevel="suppress"/>
        <TaintedInclude errorLevel="suppress"/>
        <TaintedInput errorLevel="suppress"/>
        <TaintedLdap errorLevel="suppress"/>
        <TaintedSSRF errorLevel="suppress"/>
        <TaintedShell errorLevel="suppress"/>
        <TaintedSql errorLevel="suppress"/>
        <TaintedSystemSecret errorLevel="suppress"/>
        <TaintedTextWithQuotes errorLevel="suppress"/>
        <TaintedUnserialize errorLevel="suppress"/>
        <TaintedUserSecret errorLevel="suppress"/>
        <TooFewArguments errorLevel="suppress"/>
        <TooManyArguments errorLevel="suppress"/>
        <TooManyTemplateParams errorLevel="suppress"/>
        <Trace errorLevel="suppress"/>
        <TraitMethodSignatureMismatch errorLevel="suppress"/>
        <TypeDoesNotContainNull errorLevel="suppress"/>
        <TypeDoesNotContainType errorLevel="suppress"/>
        <UncaughtThrowInGlobalScope errorLevel="suppress"/>
        <UndefinedAttributeClass errorLevel="suppress"/>
        <UndefinedClass errorLevel="suppress"/>
        <UndefinedConstant errorLevel="suppress"/>
        <UndefinedDocblockClass errorLevel="suppress"/>
        <UndefinedFunction errorLevel="suppress"/>
        <UndefinedGlobalVariable errorLevel="suppress"/>
        <UndefinedInterface errorLevel="suppress"/>
        <UndefinedInterfaceMethod errorLevel="suppress"/>
        <UndefinedMagicMethod errorLevel="suppress"/>
        <UndefinedMagicPropertyAssignment errorLevel="suppress"/>
        <UndefinedMagicPropertyFetch errorLevel="suppress"/>
        <UndefinedMethod errorLevel="suppress"/>
        <UndefinedPropertyAssignment errorLevel="suppress"/>
        <UndefinedPropertyFetch errorLevel="suppress"/>
        <UndefinedThisPropertyAssignment errorLevel="suppress"/>
        <UndefinedThisPropertyFetch errorLevel="suppress"/>
        <UndefinedTrace errorLevel="suppress"/>
        <UndefinedTrait errorLevel="suppress"/>
        <UndefinedVariable errorLevel="suppress"/>
        <UnevaluatedCode errorLevel="suppress"/>
        <UnhandledMatchCondition errorLevel="suppress"/>
        <UnimplementedAbstractMethod errorLevel="suppress"/>
        <UnimplementedInterfaceMethod errorLevel="suppress"/>
        <UninitializedProperty errorLevel="suppress"/>
        <UnnecessaryVarAnnotation errorLevel="suppress"/>
        <UnrecognizedExpression errorLevel="suppress"/>
        <UnrecognizedStatement errorLevel="suppress"/>
        <UnresolvableInclude errorLevel="suppress"/>
        <UnsafeGenericInstantiation errorLevel="suppress"/>
        <UnsafeInstantiation errorLevel="suppress"/>
        <UnusedClass errorLevel="suppress"/>
        <UnusedClosureParam errorLevel="suppress"/>
        <UnusedConstructor errorLevel="suppress"/>
        <UnusedForeachValue errorLevel="suppress"/>
        <UnusedFunctionCall errorLevel="suppress"/>
        <UnusedMethod errorLevel="suppress"/>
        <UnusedMethodCall errorLevel="suppress"/>
        <UnusedParam errorLevel="suppress"/>
        <UnusedProperty errorLevel="suppress"/>
        <UnusedPsalmSuppress errorLevel="suppress"/>
        <UnusedReturnValue errorLevel="suppress"/>
        <UnusedVariable errorLevel="suppress"/>
    </issueHandlers>
</psalm>

PHP8 promotes undefined array offset errors from E_NOTICE to E_WARNING, which breaks a lot of legacy code that was ignoring notices (yeah, bad bad bad 😉 )

The idea here is to detect absolutely all errors (errorLevel="1", ensureArrayStringOffsetsExist="true", etc), but then use <issueHandlers> to suppress everything except the array offset stuff. It's a useful technique that can be used when hunting for other categories of issues in legacy code.