path: root/doc/reference/items/language/module.qdoc

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/*!
    \contentspage list-of-language-items.html
    \previouspage JobLimit
    \nextpage ModuleProvider
    \qmltype Module
    \inqmlmodule QbsLanguageItems
    \ingroup list-of-items
    \keyword QML.Module

    \brief Represents a collection of properties and items that can be loaded into a product.

    A Module item is a collection of properties and language items. It
    contributes to building a product if the product has a
    \l{Depends}{dependency} on the module. Modules may contain the following
    items:

    \list
        \li \l{Depends}
        \li \l{FileTagger}
        \li \l{Group}
        \li \l{JobLimit}
        \li \l{Parameter}
        \li \l{Probe}
        \li \l{PropertyOptions}
        \li \l{Rule}
        \li \l{Scanner}
    \endlist

    When a product expresses a dependency on a module, \QBS will create an
    instance of the module item in the scope of the product. The product can
    then read and write properties from and to the loaded module, respectively.

    Modules in different products are isolated from each other, just as products
    cannot access each other's properties. However, products can use the
    \l{Export} item to pass dependencies and properties of modules to other
    dependent products.

    The following (somewhat artificial) module pre-processes text files by removing certain
    characters from them. The module's name is \c{txt_processor}.

    \qml
    import qbs.FileInfo
    import qbs.TextFile

    Module {
        property stringList unwantedCharacters: []

        FileTagger {
            patterns: ["*.raw"]
            fileTags: ["raw-txt"]
        }

        Rule {
            inputs: ["raw-txt"]

            Artifact {
                filePath: FileInfo.relativePath(input.filePath, product.sourceDirectory) +
                           "/" + input.fileName + ".processed"
                fileTags: ["processed-txt"]
            }

            prepare: {
                var cmd = new JavaScriptCommand();
                cmd.description = "Processing " + input.fileName;
                cmd.sourceCode = function() {
                    var inFile = new TextFile(input.filePath, TextFile.ReadOnly);
                    var content = inFile.readAll();
                    inFile.close();
                    var unwantedChars = input.txt_processor.unwantedCharacters;
                    for (var c in unwantedChars)
                        content = content.replace(unwantedChars[c], "");
                    var outFile = new TextFile(output.filePath, TextFile.WriteOnly);
                    outFile.write(content);
                    outFile.close();
                };
                return cmd;
            }
        }
    }
    \endqml

    And this is how a \l{Product} would use the module:

    \qml
    Product {
        type: "processed-txt"
        Depends { name: "txt_processor" }
        txt_processor.unwantedCharacters: ["\r"]
        files: [
            "file1.raw",
            "file2.raw"
        ]
    }
    \endqml

    The resulting files are tagged with \c{processed-txt} and might be consumed
    by a rule in another module. That is possible if another rule has
    \c{processed-txt} in its \l{Rule::inputs}{inputs} property.

    For more information about how you make your own modules available to \QBS,
    see \l{Custom Modules and Items}.

    \section1 Accessing Product and Module Properties

    When defining a property in a module item, the right-hand side expression is
    a binding. Bindings may reference other properties of:

    \list
        \li the current module
        \li other modules that this module depends on
        \li the dependent product
    \endlist

    Please note that this applies to bindings in modules only. Property access
    in rules and other nested items is different.

    \section2 Accessing Properties of the Current Module

    Sibling properties in the same module can be accessed directly by their name:

    \qml
    Module {
        property stringList windowsDefaults: ["\r"]
        property stringList unwantedCharacters: windowsDefaults
    }
    \endqml

    \section2 Properties of the Dependent Modules

    When a module loads another module through a \l{Depends} element, it can
    access properties of the other module through its name. Assuming there was a
    module \c OtherModule with a property \c otherProperty, such an access would
    look like this:

    \qml
    Module {
        Depends { name: "OtherModule" }
        property string myProperty: "something-" + OtherModule.otherProperty
    }
    \endqml

    \section2 Accessing Properties of the Dependent Product

    \qml
    Module {
        property bool featureEnabled:
                (product.type.contains("application")) ?  true : false
    }
    \endqml

    \section1 Special Property Values

    For every property defined in a module, \QBS provides the following special
    built-in values:

    \list
        \li \l base
        \li \l original
        \li \l outer
    \endlist

    \section2 \c base
    This value is useful when making use of inheritance. It stands for the value of the respective
    property in the item one level up in the inheritance chain. For instance:
    \code
    Product { // defined in MyProduct.qbs
        Depends { name: "mymodule" }
        mymodule.someProperty: ["value1"]
    }
    ------ some other file ------
    MyProduct {
        mymodule.someProperty: base.concat(["value2"]) // => ["value1", "value2"]
    }
    \endcode

    \section2 \c original
    This is the value of the property in the module itself (possibly overridden from a profile or
    the command line). Use it to set a module property conditionally:
    \code
    Module { // This is mymodule
        property string aProperty: "z"
    }
    ----------
    Product {
        Depends { name: "mymodule" }
        Depends { name: "myothermodule" }
        mymodule.aProperty: myothermodule.anotherProperty === "x" ? "y" : original // => "y" if myothermodule.anotherProperty is "x", "z" otherwise
    \endcode

    \section2 \c outer
    This value is used in nested items, where it refers to the value of the respective property
    in the surrounding item. It is only valid in \l{Group} and \l{Properties} items:
    \code
    Product {
        Depends { name: "mymodule" }
        mymodule.someProperty: ["value1"]
        Group {
            name: "special files"
            files: ["somefile1", "somefile2"]
            mymodule.someProperty: outer.concat(["value"]) // => ["value1", "value2"]
        }
    }
    \endcode


    \section1 Dependency Parameters

    Modules can declare dependency parameters. Those parameters can be set
    within \l{Depends} items. \l{Rule}{Rules} of the module can read the
    parameters of dependencies and act accordingly.

    In the following example, the module \e{foo} declares the parameter
    \c{ignore}. A dependency to \c{bar} then sets the parameter \c{foo.ignore}
    to \c{true}. A rule in \c{foo} ignores all dependencies that have
    \c{foo.ignore} set to true.

    \code
    Module {    // Definition of module 'foo'.
        Parameter { property bool ignore }
        Rule {
            ...
            prepare: {
                for (i in product.dependencies) {
                    var dep = product.dependencies[i];
                    if (dep.foo.ignore)
                        continue;
                    // Do something with the dependency.
                }
            }
        }
        ...
    }
    ----------
    Product {
        Depends { name: "foo" }
        Depends { name: "bar"; foo.ignore: true }
    }
    \endcode
*/

/*!
    \qmlproperty stringList Module::additionalProductTypes

    A list of elements that will be added to the \l{Product::type}{type}
    property of a product that has a dependency on the module.

    \defaultvalue \c []
*/

/*!
    \qmlproperty bool Module::condition

    Whether the module is enabled. If this property is \c false, the
    surrounding Module item will not be considered in the module look-up.

    \defaultvalue \c true
*/

/*!
    \qmlproperty bool Module::present
    \readonly

    This property is \c false if and only if the respective \l{Depends} item had
    its \l{Depends::required}{required} property set to \c false and the module
    was not found.

    \defaultvalue \c true
*/

/*!
    \qmlproperty int Module::priority

    The priority of this module instance. If there is more than one module
    instance available for a module name, the module with the highest priority
    is chosen.

    \defaultvalue 0
*/

/*!
    \qmlproperty script Module::setupBuildEnvironment

    A script for setting up the environment in which a product is built.

    The code in this script is treated as a function with the signature
    \c{function(project, product)}.

    Use the \l{Environment Service}{Environment} functions to alter the
    environment.

    The return value of this script is ignored.

    \nodefaultvalue
*/

/*!
    \qmlproperty script Module::setupRunEnvironment

    A script for setting up the environment in which a product is run.

    The code in this script is treated as a function with the signature
    \c{function(project, product, config)}.

    The \c config parameter is a list of arbitrary strings that can be passed
    via the \l{run} command. The values supported by specific modules are
    listed in their respective documentation.

    Use the \l{Environment Service}{Environment} functions to alter the
    environment.

    The return value of this script is ignored.

    \nodefaultvalue
*/

/*!
    \qmlproperty script Module::validate

    A script that is run after the module is loaded. It can be used to check
    property values and throw errors in unexpected cases. The return value is
    ignored.

    \nodefaultvalue
*/

/*!
    \qmlproperty string Module::version

    The module's version. It consists of integer values separated by dots. You
    can check for specific values of this property in a \l{Depends} item.
*/