Platform

Platforms are responsible for providing plarform-specific support that helps run and build the whole project. In this documentation, we will learn how to implement a platform.

A platform should implement the Platform interface, and export the instance of the class as default.

The Platform Interface

getDefaultConfig

Definition

getDefaultConfig returns an object that would be merged into the project platform configuration, whose key name is platformConfig.$PACKAGE_NAME, while $PACKAGE_NAME is the package name of current platform.

getLoaderImports

Definition

getLoaderImports should return an array of dependencies that could be used by @agros/loader's AOP to generate bootstrap code.

The definition of array item can be found here. In general, there will always be two things that should be in this array: renderer and router.

For example, in @agros/platform-react, we should import react (which is exported from @agros/platform-react/lib/react) and react-router-dom (which is exported from @agros/platform-react/lib/react-router-dom), then the getLoaderImports' value will be:

import { Platform as IPlatform } from '@agros/platforms';
class Platform implements IPlatform {
    // ...
    public getLoaderImports() {
        return [
            {
                libName: '@agros/platform-react/lib/react-router-dom',
                identifierName: 'Routes',
            },
            {
                libName: '@agros/platform-react/lib/react-router-dom',
                identifierName: 'Route',
            },
            // ...
        ];
    }
    // ...
}

提示

The import declarations of react-router-dom can also be:

{
    libName: '@agros/platform-react/lib/react-router-dom',
    identifierName: 'ReactRouter',
    type: 'default',
}

The value of type field can be default, named or namespace. If default is specified, Agros will add a declaration like import Foo from '/path/to/foo', if named is specified, it will add import { Foo } from '/path/to/foo', and import * as Foo from '/path/to/foo' with namespace.

getDecoratorImports

Definition

getDecoratorImports should return an array of dependencies that could be used by @agros/loader when transforming @Component() decorator. The return value is the same as getLoaderImports.

getBootstrapCode

Definition

getBootstrapCode should return a string value that defines the body of the entry function. It passes a value named config from string literal of code, which points to the default-exported object from the entry file of the project (usually src/index.ts).

The method passes importsMap and addVirtualFile as its parameters.

The importMap is an object whose key and value are all string. The keys of importMap are the identifierName from getLoaderImports, and the values of it are the imported identifier name. For example, the importMap of getBootstrapCode from @agros/platform-react should be:

{
    React: 'Agros$$React',
    Routes: 'Agros$$Routes',
    // ...
}

You won't care about what the true identifier names are, just use importMap[$KEY] to get them in code.

addVirtualFile is a function that can help add some file into virtual filesystem which can be read by @agros/loader.

In general, the string of code should contain the code of render function. For example, in @agros/platform-react, the code should be:

import { Platform as IPlatform } from '@agros/platforms';
class Platform implements IPlatform {
    // ...
    public getBootstrapCode(ensuredImportsMap: Record<string, string>): string {
        const reactIdentifier = ensuredImportsMap['React'] || 'React';
        const factoryIdentifier = ensuredImportsMap['factory'] || 'factory';
        return `
            const {
                module: Module,
                RouterComponent,
                routerProps,
                container = document.getElementById('root'),
            } = config;
            ${factoryIdentifier}.create(Module).then((componentInstance) => {
                const rootModuleInstance = ${factoryIdentifier}.getRootModuleInstance();
                const rootRoutes = rootModuleInstance.getProviderValue(${ensuredImportsMap['ROUTES_ROOT']});
                ${ensuredImportsMap['RouterModule']}.createRouterItems(${factoryIdentifier}, rootRoutes).then((routes) => {
                    if (routes && Array.isArray(routes) && routes.length > 0) {
                        const RootContainer = ({
                            Module,
                            routerProps = {},
                            RouterComponent = ${ensuredImportsMap['BrowserRouter'] || 'BrowserRouter'},
                        }) => {
                            const elements = ${ensuredImportsMap['createRoutes']}(routes);
                            return ${reactIdentifier}.createElement(
                                RouterComponent,
                                routerProps,
                                ${reactIdentifier}.createElement(${ensuredImportsMap['Routes'] || 'Routes'}, {}, elements),
                            );
                        };
                        ${ensuredImportsMap['render'] || 'render'}(
                            ${reactIdentifier}.createElement(RootContainer, {
                                Module,
                                RouterComponent,
                                routerProps,
                            }),
                            container,
                        );
                    } else {
                        ${ensuredImportsMap['render'] || 'render'}(
                            ${reactIdentifier}.createElement(componentInstance.getComponent()),
                            container,
                        );
                    }
                });
            });
        `;
    }
    // ...
}

信息

This code requires a createRoutes which can be invoked by ensuredImportsMap['createRoutes'], the following code is its content:

./create-routes.ts

import { RouterItem } from '@agros/common/lib/types';
import {
    createElement,
} from 'react';
import { Route } from 'react-router-dom';

export const createRoutes = (routerItems: RouterItem[], level = 0) => {
    return routerItems.map((routerItem, index) => {
        const {
            componentInstance,
            children,
            ...routeProps
        } = routerItem;
        const Component = componentInstance.getComponent();
        const { elementProps = {} } = componentInstance.metadata;

        return createElement(
            Route,
            {
                key: `level${level}_${index}`,
                ...routeProps,
                ...(
                    Component
                        ? {
                            element: createElement(Component, elementProps),
                        }
                        : {}
                ),
            },
            (Array.isArray(children) && children.length > 0) ? createRoutes(children, level + 1) : [],
        );
    });
};

getComponentFactoryCode

Definition

getComponentFactoryCode should return a string that contains the code content of a full factory function.

The method passes the following parameters:

• importsMap: same as the importsMap passed to getBootstrapCode, the key-value pairs are from the definition of getDecoratorImports
• filePath: the relative pathname (with component declaration file) of component file defined in the file field of @Component()
• identifierName: the identifier of dynamically imported component file by @agros/loader, defined as const ${identifierName} = import('filePath');
• lazy: a boolean value indicates whether the component is lazy or not

The return value of this method should be a full declaration of factory function, in general, the factory function is a single function returns platform-specified import of components. For example, in @agros/platform-react, the factory code is:

import { Platform as IPlatform } from '@agros/platforms';
class Platform implements IPlatform {
    // ...
    public getComponentFactoryCode(
        map: Record<string, string>,
        filePath: string,
        componentIdentifierName: string,
        lazy = false,
    ) {
        return `() => ${lazy ? `() => import('${filePath}')` : componentIdentifierName};`;
    }
    // ...
}

The () => import('/path/to/file') is lazy component definition of React.js.

generateComponent

generateComponent passes componentInstance and component as parameters, which means the instance of current component declaration and the imported component description file.

In general, it is optional and you can do nothing with it or simply not declare this method in a platform object since before this method being invoked by the factory, the component is already set into component instance by ComponentInstance.prototype.setComponent() method, this method provide a way to modify the component in componentInstance. For example, in @agros/platform-react, we can inject interceptor executions into it:

import { Platform as IPlatform } from '@agros/platforms';
class Platform implements IPlatform {
    // ...
    public async generateComponent<T = any>(componentInstance: ComponentInstance, component: any): Promise<T> {
        /**
         * set component directly so that it can prevent unlimited creating tasks
         */
        componentInstance.setComponent((props: any) => {
            const {
                interceptorsFallback = null,
                suspenseFallback = null,
            } = componentInstance.metadata;
            const [interceptorEnd, setInterceptorEnd] = useState<boolean>(false);

            useAsyncEffect(async () => {
                try {
                    if (Array.isArray(componentInstance.metadata.interceptorInstances)) {
                        for (const interceptorInstance of componentInstance.metadata.interceptorInstances) {
                            await interceptorInstance.intercept({
                                props,
                            });
                        }
                    }
                } finally {
                    setInterceptorEnd(true);
                }
            }, []);

            return interceptorEnd
                ? createElement(
                    Suspense,
                    {
                        fallback: suspenseFallback,
                    },
                    createElement(component, props),
                )
                : interceptorsFallback;
        });

        return component;
    }
    // ...
}

The BundlessPlatform Interface

BundlessPlatform is only designed to be used by Node.js environment since the methods in it contain some imports that cannot be recognized by Webpack. That is why the interface called BundlessPlatform. The following sections will introduce the methods in this interface.

getComponentScript

getComponentScript passes the component description file content as parameter and returns an object with type of ComponentScript, which has two fields: content and location.

Why and when should Agros need this method from platform?

When Agros loader loads the component description files whoes code are not totally pure JavaScript or TypeScript, like Vue SFC files, Svelte files, etc.

Agros will need this method to extract JavaScript or TypeScript code content and the indexes of where it starts and ends, and return them to Agros loader. That is why Agros loader need this method from platform. By the way, other platforms with pure JavaScript or TypeScript frameworks may not provide this method.

For example, in @agros/platform-vue, the definition of this method is:

import { BundlessPlatform as IBundlessPlatform } from '@agros/utils/lib/types';
import { parse } from 'vue/compiler-sfc';

class BundlessPlatform implements IBundlessPlatform {
    // ...
    public getComponentScript(source: string) {
        const ast = parse(source);
        const content = ast?.descriptor?.script?.content;
        const start = ast?.descriptor?.script?.loc?.start?.offset;
        const end = ast?.descriptor?.script?.loc?.end.offset;

        if (typeof start !== 'number' || typeof end !== 'number') {
            return {
                content,
            };
        }

        return {
            content,
            location: {
                start,
                end,
            },
        };
    }
    // ...
}

agros-platform.config.js

agros-platform.config.js is the configuration file of platform. This configuration file should export an object with type PlatformConfig.

configWebpack

This is a function which passes a default Webpack configuration object from @agros/app by module.exports. In this file, you are allowed to modify some configuration with the parameter configuration object to add some loaders, plugins and any other things.

For example, in @agros/platform-vue, the content of configWebpack is:

const { defineBuilderConfig } = require('@agros/common/lib/builder-config');
const {
    addBabelPreset,
    addBabelPlugin,
} = require('@agros/utils/lib/customizers');
const { VueLoaderPlugin } = require('vue-loader');

module.exports = {
    configWebpack: defineBuilderConfig((config) => {
        addBabelPreset(require.resolve('@babel/preset-env'))(config);
        addBabelPreset(require.resolve('@vue/babel-preset-app'))(config);
        addBabelPlugin(require.resolve('@babel/plugin-transform-typescript'))(config);
        addBabelPlugin(require.resolve('@babel/plugin-transform-runtime'))(config);
        addBabelPlugin(require.resolve('@babel/plugin-transform-parameters'))(config);

        config.module?.rules?.unshift({
            test: /\.vue$/,
            use: [
                {
                    loader: require.resolve('./lib/loaders/vue-loader.js'),
                    options: {
                        loaders: {
                            js: require.resolve('awesome-typescript-loader'),
                        },
                    },
                },
            ],
        });

        let resourceRule = config.module.rules.find((rule) => rule?.type === 'asset/resource');

        if (!resourceRule) {
            resourceRule = config.module.rules.find((rule) => !!rule.oneOf)?.oneOf?.find((rule) => {
                return rule?.type === 'asset/resource';
            });
        }

        if (resourceRule) {
            resourceRule?.exclude?.push(/\.vue$/);
        }

        config.plugins?.push(new VueLoaderPlugin());
        config.module.rules = config.module?.rules?.map((rule) => {
            if (
                typeof rule.use === 'string' && (
                    rule.use.indexOf('@agros/loader') !== -1 ||
                    /packages\/agros-loader/.test(rule.use)
                )
            ) {
                return {
                    ...rule,
                    test: /\.(js|jsx|ts|tsx|vue)$/,
                };
            }
            return rule;
        });

        return config;
    }),
};

bundlessPlatform

The relative pathname of BundlessPlatform file. For example, in @agros/platform-vue, the compiled BundlessPlatform file is located in lib/bundless-platform.js this field is:

module.exports = {
    configWebpack: './lib/bundless-platform.js',
};