given:
        def property = property()
        property.set(someValue())
        property.set((Iterable) null)

        expect:
        !property.present
        property.getOrNull() == null
        property.getOrElse(someValue()) == someValue()
        property.getOrElse(null) == null
    }

    def "can set null value to remove any added values"() {
        property.add("abc")

        given:
        property.set(notDefined())
        and:
        property.put('k1', 'v1')
        property.put('k2', Providers.of('v2'))
        property.putAll(['k3': 'v3'])
        property.putAll(Providers.of(['k4': 'v4']))

        expect:
        !property.present
        property.getOrNull() == null
        property.getOrElse(['kk': 'vv']) == ['kk': 'vv']

        when:
        property.get()
        then:

        property.get() == someValue()

        property.set(someOtherValue())
        property.present
        property.get() == someOtherValue()
    }

    def "can use null convention value"() {
        def property = propertyWithNoValue()
        assert property.getOrNull() != someValue()

        expect:
        nullConvention(property)

        !property.present
        property.getOrNull() == null

    }

    private static boolean isNameProperty(PropertyMetadata property) {
        // Property is read only, called "name", has type String and getter is abstract
        return property.isReadOnly() && "name".equals(property.getName()) && property.getType() == String.class && property.getMainGetter().isAbstract();
    }

    private static boolean hasPropertyType(PropertyMetadata property) {

<2> Reads the value from the project extra property we created — note the `project.` qualifier on `extra[...]`, otherwise Gradle will assume we want to read an extra property from the _task_

// === `Property`, `Provider` and `NamedDomainObjectProvider`


[[kotdsl:assignment]]
== Kotlin lazy property assignment

        failureDescriptionContains("- Type 'Consumer' property 'counter' doesn't have a configured value.")
        failureDescriptionContains("Reason: This property isn't marked as optional and no value has been configured.")
    }

    def "injection by name does not fail validation if service is not found but property marked as @Optional"() {
        given:
        serviceImplementation()

    }

    @Override
    public void setStatus(Object s) {
        getInternalStatus().set(s);
    }

    @Override
    public Property<Object> getInternalStatus() {
        if (status == null) {
            status = getObjects().property(Object.class).convention(DEFAULT_STATUS);
        }
        return status;
    }

    @Override
    public Map<String, Project> getChildProjectsUnchecked() {

====
include::sample[dir="snippets/files/misc/kotlin/project2",files="build.gradle.kts[tags=using-root-dir-property]"]
include::sample[dir="snippets/files/misc/groovy/project2",files="build.gradle[tags=using-root-dir-property]"]
====

        super.visitValueParameter(valueParameter)
        valueParameter.correspondingProperty?.let { visitProperty(it) }
    }

    override fun visitProperty(property: FirProperty) {
        if (visitedProperty.add(property)) {
            super.visitProperty(property)
        }
    }

    override fun visitScript(script: FirScript) {
        script.declarations.forEach {
            it.accept(this)
        }

Attempting to modify the toolchain after it has been finalized will result in error messages similar to the following:
```
The value for property 'implementation' is final and cannot be changed any further.
The value for property 'languageVersion' is final and cannot be changed any further.
The value for property 'vendor' is final and cannot be changed any further.
```