@loopback/context/dist/binding.js

"use strict";
// Copyright IBM Corp. and LoopBack contributors 2017,2020. All Rights Reserved.
// Node module: @loopback/context
// This file is licensed under the MIT License.
// License text available at https://opensource.org/licenses/MIT
Object.defineProperty(exports, "__esModule", { value: true });
exports.Binding = exports.isDynamicValueProviderClass = exports.BindingType = exports.BindingScope = void 0;
const tslib_1 = require("tslib");
const debug_1 = tslib_1.__importDefault(require("debug"));
const events_1 = require("events");
const binding_inspector_1 = require("./binding-inspector");
const binding_key_1 = require("./binding-key");
const inject_1 = require("./inject");
const interception_proxy_1 = require("./interception-proxy");
const invocation_1 = require("./invocation");
const keys_1 = require("./keys");
const resolution_session_1 = require("./resolution-session");
const resolver_1 = require("./resolver");
const value_promise_1 = require("./value-promise");
const debug = (0, debug_1.default)('loopback:context:binding');
/**
 * Scope for binding values
 */
var BindingScope;
(function (BindingScope) {
    /**
     * The binding provides a value that is calculated each time. This will be
     * the default scope if not set.
     *
     * For example, with the following context hierarchy:
     *
     * - `app` (with a binding `'b1'` that produces sequential values 0, 1, ...)
     *   - req1
     *   - req2
     *
     * Now `'b1'` is resolved to a new value each time for `app` and its
     * descendants `req1` and `req2`:
     * - app.get('b1') ==> 0
     * - req1.get('b1') ==> 1
     * - req2.get('b1') ==> 2
     * - req2.get('b1') ==> 3
     * - app.get('b1') ==> 4
     */
    BindingScope["TRANSIENT"] = "Transient";
    /**
     * @deprecated Finer-grained scopes such as `APPLICATION`, `SERVER`, or
     * `REQUEST` should be used instead to ensure the scope of sharing of resolved
     * binding values.
     *
     * The binding provides a value as a singleton within each local context. The
     * value is calculated only once per context and cached for subsequential
     * uses. Child contexts have their own value and do not share with their
     * ancestors.
     *
     * For example, with the following context hierarchy:
     *
     * - `app` (with a binding `'b1'` that produces sequential values 0, 1, ...)
     *   - req1
     *   - req2
     *
     * 1. `0` is the resolved value for `'b1'` within the `app` afterward
     * - app.get('b1') ==> 0 (always)
     *
     * 2. `'b1'` is resolved in `app` but not in `req1`, a new value `1` is
     * calculated and used for `req1` afterward
     * - req1.get('b1') ==> 1 (always)
     *
     * 3. `'b1'` is resolved in `app` but not in `req2`, a new value `2` is
     * calculated and used for `req2` afterward
     * - req2.get('b1') ==> 2 (always)
     *
     */
    BindingScope["CONTEXT"] = "Context";
    /**
     * The binding provides a value as a singleton within the context hierarchy
     * (the owning context and its descendants). The value is calculated only
     * once for the owning context and cached for subsequential uses. Child
     * contexts share the same value as their ancestors.
     *
     * For example, with the following context hierarchy:
     *
     * - `app` (with a binding `'b1'` that produces sequential values 0, 1, ...)
     *   - req1
     *   - req2
     *
     * 1. `0` is the singleton for `app` afterward
     * - app.get('b1') ==> 0 (always)
     *
     * 2. `'b1'` is resolved in `app`, reuse it for `req1`
     * - req1.get('b1') ==> 0 (always)
     *
     * 3. `'b1'` is resolved in `app`, reuse it for `req2`
     * - req2.get('b1') ==> 0 (always)
     */
    BindingScope["SINGLETON"] = "Singleton";
    /*
     * The following scopes are checked against the context hierarchy to find
     * the first matching context for a given scope in the chain. Resolved binding
     * values will be cached and shared on the scoped context. This ensures a
     * binding to have the same value for the scoped context.
     */
    /**
     * Application scope
     *
     * @remarks
     * The binding provides an application-scoped value within the context
     * hierarchy. Resolved value for this binding will be cached and shared for
     * the same application context (denoted by its scope property set to
     * `BindingScope.APPLICATION`).
     *
     */
    BindingScope["APPLICATION"] = "Application";
    /**
     * Server scope
     *
     * @remarks
     * The binding provides an server-scoped value within the context hierarchy.
     * Resolved value for this binding will be cached and shared for the same
     * server context (denoted by its scope property set to
     * `BindingScope.SERVER`).
     *
     * It's possible that an application has more than one servers configured,
     * such as a `RestServer` and a `GrpcServer`. Both server contexts are created
     * with `scope` set to `BindingScope.SERVER`. Depending on where a binding
     * is resolved:
     * - If the binding is resolved from the RestServer or below, it will be
     * cached using the RestServer context as the key.
     * - If the binding is resolved from the GrpcServer or below, it will be
     * cached using the GrpcServer context as the key.
     *
     * The same binding can resolved/shared/cached for all servers, each of which
     * has its own value for the binding.
     */
    BindingScope["SERVER"] = "Server";
    /**
     * Request scope
     *
     * @remarks
     * The binding provides an request-scoped value within the context hierarchy.
     * Resolved value for this binding will be cached and shared for the same
     * request context (denoted by its scope property set to
     * `BindingScope.REQUEST`).
     *
     * The `REQUEST` scope is very useful for controllers, services and artifacts
     * that want to have a single instance/value for a given request.
     */
    BindingScope["REQUEST"] = "Request";
})(BindingScope || (exports.BindingScope = BindingScope = {}));
/**
 * Type of the binding source
 */
var BindingType;
(function (BindingType) {
    /**
     * A fixed value
     */
    BindingType["CONSTANT"] = "Constant";
    /**
     * A function to get the value
     */
    BindingType["DYNAMIC_VALUE"] = "DynamicValue";
    /**
     * A class to be instantiated as the value
     */
    BindingType["CLASS"] = "Class";
    /**
     * A provider class with `value()` function to get the value
     */
    BindingType["PROVIDER"] = "Provider";
    /**
     * A alias to another binding key with optional path
     */
    BindingType["ALIAS"] = "Alias";
})(BindingType || (exports.BindingType = BindingType = {}));
/**
 * Adapt the ValueFactoryProvider class to be a value factory
 * @param provider - ValueFactoryProvider class
 */
function toValueFactory(provider) {
    return resolutionCtx => (0, invocation_1.invokeMethod)(provider, 'value', resolutionCtx.context, [], {
        skipInterceptors: true,
        session: resolutionCtx.options.session,
    });
}
/**
 * Check if the factory is a value factory provider class
 * @param factory - A factory function or a dynamic value provider class
 */
function isDynamicValueProviderClass(factory) {
    // Not a class
    if (typeof factory !== 'function' || !String(factory).startsWith('class ')) {
        return false;
    }
    const valueMethod = factory.value;
    return typeof valueMethod === 'function';
}
exports.isDynamicValueProviderClass = isDynamicValueProviderClass;
/**
 * Binding represents an entry in the `Context`. Each binding has a key and a
 * corresponding value getter.
 */
class Binding extends events_1.EventEmitter {
    /**
     * Scope of the binding to control how the value is cached/shared
     */
    get scope() {
        var _a;
        // Default to TRANSIENT if not set
        return (_a = this._scope) !== null && _a !== void 0 ? _a : BindingScope.TRANSIENT;
    }
    /**
     * Type of the binding value getter
     */
    get type() {
        var _a;
        return (_a = this._source) === null || _a === void 0 ? void 0 : _a.type;
    }
    get source() {
        return this._source;
    }
    /**
     * For bindings bound via `toClass()`, this property contains the constructor
     * function of the class
     */
    get valueConstructor() {
        var _a, _b;
        return ((_a = this._source) === null || _a === void 0 ? void 0 : _a.type) === BindingType.CLASS
            ? (_b = this._source) === null || _b === void 0 ? void 0 : _b.value
            : undefined;
    }
    /**
     * For bindings bound via `toProvider()`, this property contains the
     * constructor function of the provider class
     */
    get providerConstructor() {
        var _a, _b;
        return ((_a = this._source) === null || _a === void 0 ? void 0 : _a.type) === BindingType.PROVIDER
            ? (_b = this._source) === null || _b === void 0 ? void 0 : _b.value
            : undefined;
    }
    constructor(key, isLocked = false) {
        super();
        this.isLocked = isLocked;
        /**
         * Map for tag name/value pairs
         */
        this.tagMap = {};
        binding_key_1.BindingKey.validate(key);
        this.key = key.toString();
    }
    /**
     * Cache the resolved value by the binding scope
     * @param resolutionCtx - The resolution context
     * @param result - The calculated value for the binding
     */
    _cacheValue(resolutionCtx, result) {
        // Initialize the cache as a weakmap keyed by context
        if (!this._cache)
            this._cache = new WeakMap();
        if (this.scope !== BindingScope.TRANSIENT) {
            this._cache.set(resolutionCtx, result);
        }
        return result;
    }
    /**
     * Clear the cache
     */
    _clearCache() {
        if (!this._cache)
            return;
        // WeakMap does not have a `clear` method
        this._cache = new WeakMap();
    }
    /**
     * Invalidate the binding cache so that its value will be reloaded next time.
     * This is useful to force reloading a cached value when its configuration or
     * dependencies are changed.
     * **WARNING**: The state held in the cached value will be gone.
     *
     * @param ctx - Context object
     */
    refresh(ctx) {
        if (!this._cache)
            return;
        if (this.scope !== BindingScope.TRANSIENT) {
            const resolutionCtx = ctx.getResolutionContext(this);
            if (resolutionCtx != null) {
                this._cache.delete(resolutionCtx);
            }
        }
    }
    // Implementation
    getValue(ctx, optionsOrSession) {
        var _a;
        /* istanbul ignore if */
        if (debug.enabled) {
            debug('Get value for binding %s', this.key);
        }
        const options = (0, resolution_session_1.asResolutionOptions)(optionsOrSession);
        const resolutionCtx = this.getResolutionContext(ctx, options);
        if (resolutionCtx == null)
            return undefined;
        // Keep a snapshot for proxy
        const savedSession = (_a = resolution_session_1.ResolutionSession.fork(options.session)) !== null && _a !== void 0 ? _a : new resolution_session_1.ResolutionSession();
        // First check cached value for non-transient
        if (this._cache) {
            if (this.scope !== BindingScope.TRANSIENT) {
                if (resolutionCtx && this._cache.has(resolutionCtx)) {
                    const value = this._cache.get(resolutionCtx);
                    return this.getValueOrProxy(resolutionCtx, { ...options, session: savedSession }, value);
                }
            }
        }
        const resolutionMetadata = {
            context: resolutionCtx,
            binding: this,
            options,
        };
        if (typeof this._getValue === 'function') {
            const result = resolution_session_1.ResolutionSession.runWithBinding(s => {
                const optionsWithSession = {
                    ...options,
                    session: s,
                    // Force to be the non-proxy version
                    asProxyWithInterceptors: false,
                };
                // We already test `this._getValue` is a function. It's safe to assert
                // that `this._getValue` is not undefined.
                return this._getValue({
                    ...resolutionMetadata,
                    options: optionsWithSession,
                });
            }, this, options.session);
            const value = this._cacheValue(resolutionCtx, result);
            return this.getValueOrProxy(resolutionCtx, { ...options, session: savedSession }, value);
        }
        // `@inject.binding` adds a binding without _getValue
        if (options.optional)
            return undefined;
        return Promise.reject(new resolution_session_1.ResolutionError(`No value was configured for binding ${this.key}.`, resolutionMetadata));
    }
    getValueOrProxy(resolutionCtx, options, value) {
        const session = options.session;
        session.pushBinding(this);
        return Binding.valueOrProxy({
            context: resolutionCtx,
            binding: this,
            options,
        }, value);
    }
    /**
     * Locate and validate the resolution context
     * @param ctx - Current context
     * @param options - Resolution options
     */
    getResolutionContext(ctx, options) {
        const resolutionCtx = ctx.getResolutionContext(this);
        switch (this.scope) {
            case BindingScope.APPLICATION:
            case BindingScope.SERVER:
            case BindingScope.REQUEST:
                if (resolutionCtx == null) {
                    const msg = `Binding "${this.key}" in context "${ctx.name}" cannot` +
                        ` be resolved in scope "${this.scope}"`;
                    if (options.optional) {
                        debug(msg);
                        return undefined;
                    }
                    throw new Error(msg);
                }
        }
        const ownerCtx = ctx.getOwnerContext(this.key);
        if (ownerCtx != null && !ownerCtx.isVisibleTo(resolutionCtx)) {
            const msg = `Resolution context "${resolutionCtx === null || resolutionCtx === void 0 ? void 0 : resolutionCtx.name}" does not have ` +
                `visibility to binding "${this.key} (scope:${this.scope})" in context "${ownerCtx.name}"`;
            if (options.optional) {
                debug(msg);
                return undefined;
            }
            throw new Error(msg);
        }
        return resolutionCtx;
    }
    /**
     * Lock the binding so that it cannot be rebound
     */
    lock() {
        this.isLocked = true;
        return this;
    }
    /**
     * Emit a `changed` event
     * @param operation - Operation that makes changes
     */
    emitChangedEvent(operation) {
        const event = { binding: this, operation, type: 'changed' };
        this.emit('changed', event);
    }
    /**
     * Tag the binding with names or name/value objects. A tag has a name and
     * an optional value. If not supplied, the tag name is used as the value.
     *
     * @param tags - A list of names or name/value objects. Each
     * parameter can be in one of the following forms:
     * - string: A tag name without value
     * - string[]: An array of tag names
     * - TagMap: A map of tag name/value pairs
     *
     * @example
     * ```ts
     * // Add a named tag `controller`
     * binding.tag('controller');
     *
     * // Add two named tags: `controller` and `rest`
     * binding.tag('controller', 'rest');
     *
     * // Add two tags
     * // - `controller` (name = 'controller')
     * // `{name: 'my-controller'}` (name = 'name', value = 'my-controller')
     * binding.tag('controller', {name: 'my-controller'});
     *
     * ```
     */
    tag(...tags) {
        for (const t of tags) {
            if (typeof t === 'string') {
                this.tagMap[t] = t;
            }
            else if (Array.isArray(t)) {
                // Throw an error as TypeScript cannot exclude array from TagMap
                throw new Error('Tag must be a string or an object (but not array): ' + t);
            }
            else {
                Object.assign(this.tagMap, t);
            }
        }
        this.emitChangedEvent('tag');
        return this;
    }
    /**
     * Get an array of tag names
     */
    get tagNames() {
        return Object.keys(this.tagMap);
    }
    /**
     * Set the binding scope
     * @param scope - Binding scope
     */
    inScope(scope) {
        if (this._scope !== scope)
            this._clearCache();
        this._scope = scope;
        this.emitChangedEvent('scope');
        return this;
    }
    /**
     * Apply default scope to the binding. It only changes the scope if it's not
     * set yet
     * @param scope - Default binding scope
     */
    applyDefaultScope(scope) {
        if (!this._scope) {
            this.inScope(scope);
        }
        return this;
    }
    /**
     * Set the `_getValue` function
     * @param getValue - getValue function
     */
    _setValueGetter(getValue) {
        // Clear the cache
        this._clearCache();
        this._getValue = resolutionCtx => {
            return getValue(resolutionCtx);
        };
        this.emitChangedEvent('value');
    }
    /**
     * Bind the key to a constant value. The value must be already available
     * at binding time, it is not allowed to pass a Promise instance.
     *
     * @param value - The bound value.
     *
     * @example
     *
     * ```ts
     * ctx.bind('appName').to('CodeHub');
     * ```
     */
    to(value) {
        if ((0, value_promise_1.isPromiseLike)(value)) {
            // Promises are a construct primarily intended for flow control:
            // In an algorithm with steps 1 and 2, we want to wait for the outcome
            // of step 1 before starting step 2.
            //
            // Promises are NOT a tool for storing values that may become available
            // in the future, depending on the success or a failure of a background
            // async task.
            //
            // Values stored in bindings are typically accessed only later,
            // in a different turn of the event loop or the Promise micro-queue.
            // As a result, when a promise is stored via `.to()` and is rejected
            // later, then more likely than not, there will be no error (catch)
            // handler registered yet, and Node.js will print
            // "Unhandled Rejection Warning".
            throw new Error('Promise instances are not allowed for constant values ' +
                'bound via ".to()". Register an async getter function ' +
                'via ".toDynamicValue()" instead.');
        }
        /* istanbul ignore if */
        if (debug.enabled) {
            debug('Bind %s to constant:', this.key, value);
        }
        this._source = {
            type: BindingType.CONSTANT,
            value,
        };
        this._setValueGetter(resolutionCtx => {
            return Binding.valueOrProxy(resolutionCtx, value);
        });
        return this;
    }
    /**
     * Bind the key to a computed (dynamic) value.
     *
     * @param factoryFn - The factory function creating the value.
     *   Both sync and async functions are supported.
     *
     * @example
     *
     * ```ts
     * // synchronous
     * ctx.bind('now').toDynamicValue(() => Date.now());
     *
     * // asynchronous
     * ctx.bind('something').toDynamicValue(
     *  async () => Promise.delay(10).then(doSomething)
     * );
     * ```
     */
    toDynamicValue(factory) {
        /* istanbul ignore if */
        if (debug.enabled) {
            debug('Bind %s to dynamic value:', this.key, factory);
        }
        this._source = {
            type: BindingType.DYNAMIC_VALUE,
            value: factory,
        };
        let factoryFn;
        if (isDynamicValueProviderClass(factory)) {
            factoryFn = toValueFactory(factory);
        }
        else {
            factoryFn = factory;
        }
        this._setValueGetter(resolutionCtx => {
            const value = factoryFn(resolutionCtx);
            return Binding.valueOrProxy(resolutionCtx, value);
        });
        return this;
    }
    static valueOrProxy(resolutionCtx, value) {
        if (!resolutionCtx.options.asProxyWithInterceptors)
            return value;
        return createInterceptionProxyFromInstance(value, resolutionCtx.context, resolutionCtx.options.session);
    }
    /**
     * Bind the key to a value computed by a Provider.
     *
     * * @example
     *
     * ```ts
     * export class DateProvider implements Provider<Date> {
     *   constructor(@inject('stringDate') private param: String){}
     *   value(): Date {
     *     return new Date(param);
     *   }
     * }
     * ```
     *
     * @param provider - The value provider to use.
     */
    toProvider(providerClass) {
        /* istanbul ignore if */
        if (debug.enabled) {
            debug('Bind %s to provider %s', this.key, providerClass.name);
        }
        this._source = {
            type: BindingType.PROVIDER,
            value: providerClass,
        };
        this._setValueGetter(resolutionCtx => {
            const providerOrPromise = (0, resolver_1.instantiateClass)(providerClass, resolutionCtx.context, resolutionCtx.options.session);
            const value = (0, value_promise_1.transformValueOrPromise)(providerOrPromise, p => p.value());
            return Binding.valueOrProxy(resolutionCtx, value);
        });
        return this;
    }
    /**
     * Bind the key to an instance of the given class.
     *
     * @param ctor - The class constructor to call. Any constructor
     *   arguments must be annotated with `@inject` so that
     *   we can resolve them from the context.
     */
    toClass(ctor) {
        /* istanbul ignore if */
        if (debug.enabled) {
            debug('Bind %s to class %s', this.key, ctor.name);
        }
        this._source = {
            type: BindingType.CLASS,
            value: ctor,
        };
        this._setValueGetter(resolutionCtx => {
            const value = (0, resolver_1.instantiateClass)(ctor, resolutionCtx.context, resolutionCtx.options.session);
            return Binding.valueOrProxy(resolutionCtx, value);
        });
        return this;
    }
    /**
     * Bind to a class optionally decorated with `@injectable`. Based on the
     * introspection of the class, it calls `toClass/toProvider/toDynamicValue`
     * internally. The current binding key will be preserved (not being overridden
     * by the key inferred from the class or options).
     *
     * This is similar to {@link createBindingFromClass} but applies to an
     * existing binding.
     *
     * @example
     *
     * ```ts
     * @injectable({scope: BindingScope.SINGLETON, tags: {service: 'MyService}})
     * class MyService {
     *   // ...
     * }
     *
     * const ctx = new Context();
     * ctx.bind('services.MyService').toInjectable(MyService);
     * ```
     *
     * @param ctor - A class decorated with `@injectable`.
     */
    toInjectable(ctor) {
        this.apply((0, binding_inspector_1.bindingTemplateFor)(ctor));
        return this;
    }
    /**
     * Bind the key to an alias of another binding
     * @param keyWithPath - Target binding key with optional path,
     * such as `servers.RestServer.options#apiExplorer`
     */
    toAlias(keyWithPath) {
        /* istanbul ignore if */
        if (debug.enabled) {
            debug('Bind %s to alias %s', this.key, keyWithPath);
        }
        this._source = {
            type: BindingType.ALIAS,
            value: keyWithPath,
        };
        this._setValueGetter(({ context, options }) => {
            return context.getValueOrPromise(keyWithPath, options);
        });
        return this;
    }
    /**
     * Unlock the binding
     */
    unlock() {
        this.isLocked = false;
        return this;
    }
    /**
     * Apply one or more template functions to set up the binding with scope,
     * tags, and other attributes as a group.
     *
     * @example
     * ```ts
     * const serverTemplate = (binding: Binding) =>
     *   binding.inScope(BindingScope.SINGLETON).tag('server');
     *
     * const serverBinding = new Binding<RestServer>('servers.RestServer1');
     * serverBinding.apply(serverTemplate);
     * ```
     * @param templateFns - One or more functions to configure the binding
     */
    apply(...templateFns) {
        for (const fn of templateFns) {
            fn(this);
        }
        return this;
    }
    /**
     * Convert to a plain JSON object
     */
    toJSON() {
        var _a, _b, _c, _d;
        const json = {
            key: this.key,
            scope: this.scope,
            tags: this.tagMap,
            isLocked: this.isLocked,
        };
        if (this.type != null) {
            json.type = this.type;
        }
        switch ((_a = this._source) === null || _a === void 0 ? void 0 : _a.type) {
            case BindingType.CLASS:
                json.valueConstructor = (_b = this._source) === null || _b === void 0 ? void 0 : _b.value.name;
                break;
            case BindingType.PROVIDER:
                json.providerConstructor = (_c = this._source) === null || _c === void 0 ? void 0 : _c.value.name;
                break;
            case BindingType.ALIAS:
                json.alias = (_d = this._source) === null || _d === void 0 ? void 0 : _d.value.toString();
                break;
        }
        return json;
    }
    /**
     * Inspect the binding to return a json representation of the binding information
     * @param options - Options to control what information should be included
     */
    inspect(options = {}) {
        options = {
            includeInjections: false,
            ...options,
        };
        const json = this.toJSON();
        if (options.includeInjections) {
            const injections = (0, inject_1.inspectInjections)(this);
            if (Object.keys(injections).length)
                json.injections = injections;
        }
        return json;
    }
    /**
     * A static method to create a binding so that we can do
     * `Binding.bind('foo').to('bar');` as `new Binding('foo').to('bar')` is not
     * easy to read.
     * @param key - Binding key
     */
    static bind(key) {
        return new Binding(key);
    }
    /**
     * Create a configuration binding for the given key
     *
     * @example
     * ```ts
     * const configBinding = Binding.configure('servers.RestServer.server1')
     *   .to({port: 3000});
     * ```
     *
     * @typeParam V Generic type for the configuration value (not the binding to
     * be configured)
     *
     * @param key - Key for the binding to be configured
     */
    static configure(key) {
        return new Binding(binding_key_1.BindingKey.buildKeyForConfig(key)).tag({
            [keys_1.ContextTags.CONFIGURATION_FOR]: key.toString(),
        });
    }
    // eslint-disable-next-line @typescript-eslint/no-explicit-any
    on(event, listener) {
        return super.on(event, listener);
    }
    // eslint-disable-next-line @typescript-eslint/no-explicit-any
    once(event, listener) {
        return super.once(event, listener);
    }
}
exports.Binding = Binding;
function createInterceptionProxyFromInstance(instOrPromise, context, session) {
    return (0, value_promise_1.transformValueOrPromise)(instOrPromise, inst => {
        if (typeof inst !== 'object' || inst == null)
            return inst;
        return (0, interception_proxy_1.createProxyWithInterceptors)(
        // Cast inst from `T` to `object`
        inst, context, session);
    });
}
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