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Introduce the Context to the backend again
Signed-off-by: Fredrik Adelöw <freben@gmail.com>
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| Original file line number | Diff line number | Diff line change |
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| --- | ||
| '@backstage/backend-common': patch | ||
| --- | ||
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| Added a Context class for the backend, that handles aborting, timeouts, api resolution etc |
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| /* | ||
| * Copyright 2021 The Backstage Authors | ||
| * | ||
| * Licensed under the Apache License, Version 2.0 (the "License"); | ||
| * you may not use this file except in compliance with the License. | ||
| * You may obtain a copy of the License at | ||
| * | ||
| * http://www.apache.org/licenses/LICENSE-2.0 | ||
| * | ||
| * Unless required by applicable law or agreed to in writing, software | ||
| * distributed under the License is distributed on an "AS IS" BASIS, | ||
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
| * See the License for the specific language governing permissions and | ||
| * limitations under the License. | ||
| */ | ||
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| import { Duration } from 'luxon'; | ||
| import { RootContext } from './RootContext'; | ||
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| describe('RootContext', () => { | ||
| it('can perform a manual abort', async () => { | ||
| const { ctx, abort } = RootContext.create().withAbort(); | ||
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| const cb = jest.fn(); | ||
| ctx.abortSignal.addEventListener('abort', cb); | ||
| ctx.abortPromise.then(cb); | ||
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| abort(); | ||
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| await ctx.abortPromise; | ||
| expect(cb).toBeCalledTimes(2); | ||
| }); | ||
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| it('can abort on a timeout', async () => { | ||
| const ctx = RootContext.create().withTimeout(Duration.fromMillis(200)); | ||
| const start = Date.now(); | ||
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| const cb = jest.fn(); | ||
| ctx.abortSignal.addEventListener('abort', cb); | ||
| ctx.abortPromise.then(cb); | ||
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| await ctx.abortPromise; | ||
| const delta = Date.now() - start; | ||
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| expect(delta).toBeGreaterThan(100); | ||
| expect(delta).toBeLessThan(300); | ||
| expect(cb).toBeCalledTimes(2); | ||
| }); | ||
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| it('can apply behaviors', () => { | ||
| const ctx = RootContext.create().with( | ||
| c => c.withValue('a', 1), | ||
| c => c.withValue<number>('a', p => p! + 1), | ||
| c => c.withValue('b', 3), | ||
| ); | ||
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| expect(ctx.value('a')).toBe(2); | ||
| expect(ctx.value('b')).toBe(3); | ||
| }); | ||
| }); |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,123 @@ | ||
| /* | ||
| * Copyright 2021 The Backstage Authors | ||
| * | ||
| * Licensed under the Apache License, Version 2.0 (the "License"); | ||
| * you may not use this file except in compliance with the License. | ||
| * You may obtain a copy of the License at | ||
| * | ||
| * http://www.apache.org/licenses/LICENSE-2.0 | ||
| * | ||
| * Unless required by applicable law or agreed to in writing, software | ||
| * distributed under the License is distributed on an "AS IS" BASIS, | ||
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
| * See the License for the specific language governing permissions and | ||
| * limitations under the License. | ||
| */ | ||
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| import { DateTime, Duration } from 'luxon'; | ||
| import { AbortSignal } from 'node-abort-controller'; | ||
| import { | ||
| abortManually, | ||
| abortOnTimeout, | ||
| ContextAbortState, | ||
| } from './features/abort'; | ||
| import { | ||
| ContextValues, | ||
| findInContextValues, | ||
| unshiftContextValues, | ||
| } from './features/values'; | ||
| import { Context, ContextDecorator } from './types'; | ||
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| // The context value key used for holding abort related state | ||
| const abortKey = Symbol('Context.abort'); | ||
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| /** | ||
| * A context that is meant to be passed as a ctx variable down the call chain, | ||
| * to pass along scoped information and abort signals. | ||
| * | ||
| * @public | ||
| */ | ||
| export class RootContext implements Context { | ||
| /** | ||
| * Creates a root context. | ||
| * | ||
| * @remarks | ||
| * | ||
| * This should normally only be called near the root of an application. The | ||
| * created context is meant to be passed down into deeper levels, which may | ||
| * or may not make derived contexts out of it. | ||
| */ | ||
| static create() { | ||
| return new RootContext(undefined).withValue<ContextAbortState>( | ||
| abortKey, | ||
| abortManually(), | ||
| ); | ||
| } | ||
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| /** | ||
| * {@inheritdoc Context.abortSignal} | ||
| */ | ||
| public get abortSignal(): AbortSignal { | ||
| return this.value<ContextAbortState>(abortKey)!.signal; | ||
| } | ||
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| /** | ||
| * {@inheritdoc Context.abortPromise} | ||
| */ | ||
| public get abortPromise(): Promise<void> { | ||
| return this.value<ContextAbortState>(abortKey)!.promise; | ||
| } | ||
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| /** | ||
| * {@inheritdoc Context.deadline} | ||
| */ | ||
| public get deadline(): DateTime | undefined { | ||
| return this.value<ContextAbortState>(abortKey)!.deadline; | ||
| } | ||
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| private constructor(private readonly values: ContextValues) {} | ||
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| /** | ||
| * {@inheritdoc Context.withAbort} | ||
| */ | ||
| withAbort(): { ctx: Context; abort: () => void } { | ||
| const state = abortManually(this.value<ContextAbortState>(abortKey)); | ||
| return { | ||
| ctx: this.withValue(abortKey, state), | ||
| abort: state.abort, | ||
| }; | ||
| } | ||
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| /** | ||
| * {@inheritdoc Context.withTimeout} | ||
| */ | ||
| withTimeout(timeout: Duration): Context { | ||
| return this.withValue<ContextAbortState>(abortKey, previous => | ||
| abortOnTimeout(timeout, previous), | ||
| ); | ||
| } | ||
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| /** | ||
| * {@inheritdoc Context.with} | ||
| */ | ||
| with(...items: ContextDecorator[]): Context { | ||
| return items.reduce<Context>((prev, curr) => curr(prev), this); | ||
| } | ||
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| /** | ||
| * {@inheritdoc Context.withValue} | ||
| */ | ||
| withValue<T = unknown>( | ||
| key: string | symbol, | ||
| value: T | ((previous: T | undefined) => T), | ||
| ): Context { | ||
| return new RootContext(unshiftContextValues(this.values, key, value)); | ||
| } | ||
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| /** | ||
| * {@inheritdoc Context.value} | ||
| */ | ||
| value<T = unknown>(key: string | symbol): T | undefined { | ||
| return findInContextValues<T>(this.values, key); | ||
| } | ||
| } |
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