qmllint

qmllint is a tool shipped with Qt, that verifies the syntatic validity of QML files. You can integrate qmllint into your build system for ease of use. It also warns about some QML anti-patterns. See {Configuring qmllint warnings} for how to disable a specific warning type.

By default, some issues will result in warnings that will be printed. If there are more warnings than a limit which can be configured with --max-warnings, the exit code will be non-zero. Minor issues however (such as unused imports) are just informational messages by default and will never affect the exit code. qmllint is very configurable and allows for disabling warnings or changing how they are treated.

qmllint warns about:

• Unqualified accesses of properties
• Usage of signal handlers without a matching signal
• Usage of with statements in QML
• Issues related to compiling QML code
• Unused imports
• Deprecated components and properties
• And many other things

See QML Lint Warning and Errors on how to fix qmllint warnings and errors.

To get an overview and explanation of all available command line options, run qmllint --help.

Compiler warnings

qmllint can warn you about code that cannot be compiled by qmlsc.

These warnings are not enabled by default. In order to enable them, configure qmllint to use the compiler warning category.

Using qmllint with CMake

For projects using the qt_add_qml_module() CMake API for creating QML modules, convenience targets such as all_qmllint are created automatically. These run qmllint on all the QML files of a specific module or of the project.

Marking components and properties as deprecated

qmllint allows you to mark both properties and components as deprecated:

@Deprecated { reason: "Use NewCustomText instead" }
Text {
    @Deprecated { reason: "Use newProperty instead" }
    property int oldProperty
    property int newProperty
    Component.onCompleted: console.log(oldProperty);  // Warning: XY.qml:8:40: Property "oldProperty" is deprecated (Reason: Use newProperty instead)
}

Deprecation warnings for components will be shown every time the component is created.

Disabling warnings inline

You may at any point disable warnings temporarily in a file using // qmllint disable.

You can do this at the end of a line when a single line produces warnings:

Item {
    property string foo
    Item {
        property string bar: foo // qmllint disable unqualified
    }
}

Alternatively you can disable comments for a block of lines by putting the comment in a line only containing // qmllint disable, ending the block with // qmllint enable:

Item {
    property string foo
    Item {
        // qmllint disable unqualified
        property string bar: foo
        property string bar2: foo
        // qmllint enable unqualified
    }
}

qmllint interprets all single line comments starting with qmllint as directives. Thus you may not start a comment that way unless you wish to enable or disable warnings.

Configuring qmllint warnings

You can configure the warnings that qmllint emits and their severity level. These levels can be info, {warning}, error, or disable. You can customize the warnings using the .qmllint.ini settings file or by passing command line options to qmllint. Command line options override the default and the settings file.

To customize the level of a warning category via the command line, set the corresponding command line option to the desired level.

For example, to disable warnings about deprecations, call qmllint with the --deprecated=disable option. And to turn unused imports into an error, pass --unused-imports=error.

Customizing warnings in a more permanent way can be done by modifying the settings file. See the upcoming section on Settings files for more details.

Settings

In addition to passing command-line options, you can also configure qmllint via a settings file. The command line --write-defaults will generate one for you.

Setting files are named .qmllint.ini and look like this:

[General]
DisableDefaultImports=false
MaxWarnings=-1

[Warnings]
AccessSingletonViaObject=warning
AliasCycle=warning
AssignmentInCondition=warning
AttachedPropertyReuse=disable
BadSignalHandlerParameters=warning
Comma=warning
CompilerWarnings=disable
ComponentChildrenCount=warning
ConfusingExpressionStatement=warning
ConfusingMinuses=warning
ConfusingPluses=warning
ContextProperties=warning
Deprecated=warning
DuplicateEnumEntries=warning
DuplicateImport=warning
DuplicateInlineComponent=warning
DuplicatePropertyBinding=warning
DuplicatedName=warning
EnumEntryMatchesEnum=warning
EnumsAreNotTypes=warning
EqualityTypeCoercion=warning
Eval=warning
FunctionUsedBeforeDeclaration=disable
ImportFailure=warning
IncompatibleType=warning
InheritanceCycle=warning
InvalidLintDirective=warning
LintPluginWarnings=disable
LiteralConstructor=warning
MissingEnumEntry=warning
MissingProperty=warning
MissingType=warning
MultilineStrings=info
NonListProperty=warning
NonRootEnum=warning
PreferNonVarProperties=warning
PrefixedImportType=warning
PropertyAliasCycles=warning
QtDesignStudio.FunctionsNotSupportedInQmlUi=warning
QtDesignStudio.ImperativeCodeNotEditableInVisualDesigner=warning
QtDesignStudio.InvalidIdeInVisualDesigner=warning
QtDesignStudio.ReferenceToParentItemNotSupportedByVisualDesigner=warning
QtDesignStudio.UnsupportedRootTypeInQmlUi=warning
QtDesignStudio.UnsupportedTypeInQmlUi=warning
Quick.Anchors=warning
Quick.AttachedPropertyReuse=disable
Quick.AttachedPropertyType=warning
Quick.Color=warning
Quick.ControlsAttachedPropertyReuse=disable
Quick.ControlsNativeCustomize=warning
Quick.LayoutsPositioning=warning
Quick.PropertyChangesParsed=warning
Quick.StateNoChildItem=warning
Quick.UnexpectedVarType=warning
ReadOnlyProperty=warning
RedundantOptionalChaining=warning
RequiredProperty=warning
RestrictedType=warning
StalePropertyRead=warning
TopLevelComponent=warning
TranslationFunctionMismatch=warning
UncreatableType=warning
UnintentionalEmptyBlock=warning
UnqualifiedAccess=warning
UnreachableCode=warning
UnresolvedAlias=warning
UnresolvedType=warning
UnterminatedCase=warning
UnusedImports=info
UseProperFunction=warning
VarUsedBeforeDeclaration=warning
Void=disable
WithStatement=warning

Warning levels may be set to info, warning, error, or disable just as with command line options.

qmllint will automatically look for a settings file at the location of the qml file that is being linted. It also looks through all parent directories to find this file and automatically applies the settings therein. You can disable this behavior by using --ignore-settings. You may always override these defaults by specifying command line parameters that take precedence over the warning levels in settings.

Context property settings

Context properties can be defined or ignored by name in their own settings file. Context property settings allow a more fine-grained approach to disabling unqualified access warnings for context property usages, while .qmllint.ini only allows to disable all unqualified access warnings, potentially including non-context property related ones.

Context property settings are named .contextProperties.ini and should be located inside the source folder of your project. They look like this:

[General]
disableUnqualifiedAccess = "myContextProperty1,myContextProperty2"
warnOnUsage = "myContextProperty3,myContextProperty4,myContextProperty5"
disableHeuristic = false

To disable qmllint warnings about unqualified access to a context property name, add the context property name to disableUnqualifiedAccess. Separate multiple context property names with a comma.

To warn about context property usages, add the context property name to warnOnUsage. Separate multiple context property names with a comma.

To control the qmllint heuristic, set disableHeuristic to true or false.

Scripting

qmllint can write or output JSON via the --json <file> option which will return valid JSON with warning messages, file and line location of warnings, and their severity level. Use the special filename '-' to write to stdout instead of a file. This can be used to more easily integrate qmllint in your pre-commit hooks or CI testing.