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remove the middleware part of context composition

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Signed-off-by: Fredrik Adelöw <freben@gmail.com>
This commit is contained in:
Fredrik Adelöw
2022-01-24 15:23:37 +01:00
parent c78bf4acd4
commit 5045671d32
11 changed files with 63 additions and 107 deletions
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packages/backend-common/api-report.md
+9 -9
View File
@@ -151,23 +151,23 @@ export interface ContainerRunner {
export interface Context {
readonly abortSignal: AbortSignal_2;
readonly deadline: Date | undefined;
use(...decorators: ContextDecorator[]): Context;
value<T = unknown>(key: string): T | undefined;
}
// @public
export type ContextDecorator = (ctx: Context) => Context;
// @public
export class Contexts {
static root(): Context;
static setAbort(source: AbortController_2 | AbortSignal_2): ContextDecorator;
static setTimeoutDuration(timeout: Duration): ContextDecorator;
static setTimeoutMillis(timeout: number): ContextDecorator;
static setValue(
static withAbort(
parentCtx: Context,
source: AbortController_2 | AbortSignal_2,
): Context;
static withTimeoutDuration(parentCtx: Context, timeout: Duration): Context;
static withTimeoutMillis(parentCtx: Context, timeout: number): Context;
static withValue(
parentCtx: Context,
key: string,
value: unknown | ((previous: unknown | undefined) => unknown),
): ContextDecorator;
): Context;
}
// @public @deprecated
packages/backend-common/src/context/AbortContext.test.ts
-12
View File
@@ -16,7 +16,6 @@
import { AbortController } from 'node-abort-controller';
import { AbortContext } from './AbortContext';
import { Contexts } from './Contexts';
import { RootContext } from './RootContext';
describe('AbortContext', () => {
@@ -343,15 +342,4 @@ describe('AbortContext', () => {
expect(childListener).toBeCalledTimes(0);
});
});
it('can decorate', () => {
const root = new RootContext();
const controller = new AbortController();
const parent = AbortContext.forSignal(root, controller.signal);
const child = parent.use(
Contexts.setValue('a', 2),
Contexts.setValue('a', 3),
);
expect(child.value('a')).toBe(3);
});
});
packages/backend-common/src/context/AbortContext.ts
+1 -5
View File
@@ -15,7 +15,7 @@
*/
import { AbortController, AbortSignal } from 'node-abort-controller';
import { Context, ContextDecorator } from './types';
import { Context } from './types';
/**
* A context that implements various abort related functionality.
@@ -130,8 +130,4 @@ export class AbortContext implements Context {
value<T = unknown>(key: string): T | undefined {
return this.parent.value(key);
}
use(...items: ContextDecorator[]): Context {
return items.reduce((prev, curr) => curr(prev), this as Context);
}
}
packages/backend-common/src/context/Contexts.test.ts
+7 -6
View File
@@ -35,7 +35,7 @@ describe('Contexts', () => {
it('works for controllers', () => {
const controller = new AbortController();
const parent = Contexts.root();
const child = parent.use(Contexts.setAbort(controller));
const child = Contexts.withAbort(parent, controller);
expect(child.abortSignal.aborted).toBe(false);
controller.abort();
expect(child.abortSignal.aborted).toBe(true);
@@ -44,7 +44,7 @@ describe('Contexts', () => {
it('works for signals', () => {
const controller = new AbortController();
const parent = Contexts.root();
const child = parent.use(Contexts.setAbort(controller.signal));
const child = Contexts.withAbort(parent, controller.signal);
expect(child.abortSignal.aborted).toBe(false);
controller.abort();
expect(child.abortSignal.aborted).toBe(true);
@@ -55,8 +55,9 @@ describe('Contexts', () => {
it('works', () => {
jest.useFakeTimers();
const parent = Contexts.root();
const child = parent.use(
Contexts.setTimeoutDuration(Duration.fromMillis(200)),
const child = Contexts.withTimeoutDuration(
parent,
Duration.fromMillis(200),
);
expect(child.abortSignal.aborted).toBe(false);
jest.advanceTimersByTime(100);
@@ -70,7 +71,7 @@ describe('Contexts', () => {
it('works', () => {
jest.useFakeTimers();
const parent = Contexts.root();
const child = parent.use(Contexts.setTimeoutMillis(200));
const child = Contexts.withTimeoutMillis(parent, 200);
expect(child.abortSignal.aborted).toBe(false);
jest.advanceTimersByTime(100);
expect(child.abortSignal.aborted).toBe(false);
@@ -82,7 +83,7 @@ describe('Contexts', () => {
describe('setValue', () => {
it('works', () => {
const parent = Contexts.root();
const child = parent.use(Contexts.setValue('k', 'v'));
const child = Contexts.withValue(parent, 'k', 'v');
expect(child.value('k')).toBe('v');
});
});
packages/backend-common/src/context/Contexts.ts
+25 -21
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@@ -18,7 +18,7 @@ import { Duration } from 'luxon';
import { AbortController, AbortSignal } from 'node-abort-controller';
import { AbortContext } from './AbortContext';
import { RootContext } from './RootContext';
import { Context, ContextDecorator } from './types';
import { Context } from './types';
import { ValueContext } from './ValueContext';
/**
@@ -51,15 +51,18 @@ export class Contexts {
* If the given source was already aborted, then a new already-aborted context
* is returned.
*
* @param parentCtx - A parent context that shall be used as a base
* @param source - An abort controller or signal that you intend to perhaps
* trigger at some later point in time.
* @returns A decorator that can be passed to {@link Context.use}
* @returns A new {@link Context}
*/
static setAbort(source: AbortController | AbortSignal): ContextDecorator {
return ctx =>
'aborted' in source
? AbortContext.forSignal(ctx, source)
: AbortContext.forController(ctx, source);
static withAbort(
parentCtx: Context,
source: AbortController | AbortSignal,
): Context {
return 'aborted' in source
? AbortContext.forSignal(parentCtx, source)
: AbortContext.forController(parentCtx, source);
}
/**
@@ -67,13 +70,13 @@ export class Contexts {
* any parent context signals, or when the given amount of time has passed.
* This may affect the deadline.
*
* @param parentCtx - A parent context that shall be used as a base
* @param timeout - The duration of time, after which the derived context will
* signal to abort.
* @returns A decorator that can be passed to {@link Context.use}
* @returns A new {@link Context}
*/
static setTimeoutDuration(timeout: Duration): ContextDecorator {
return ctx =>
AbortContext.forTimeoutMillis(ctx, timeout.as('milliseconds'));
static withTimeoutDuration(parentCtx: Context, timeout: Duration): Context {
return AbortContext.forTimeoutMillis(parentCtx, timeout.as('milliseconds'));
}
/**
@@ -81,30 +84,31 @@ export class Contexts {
* any parent context signals, or when the given amount of time has passed.
* This may affect the deadline.
*
* @param parentCtx - A parent context that shall be used as a base
* @param timeout - The number of milliseconds, after which the derived
* context will signal to abort.
* @returns A decorator that can be passed to {@link Context.use}
* @returns A new {@link Context}
*/
static setTimeoutMillis(timeout: number): ContextDecorator {
return ctx => AbortContext.forTimeoutMillis(ctx, timeout);
static withTimeoutMillis(parentCtx: Context, timeout: number): Context {
return AbortContext.forTimeoutMillis(parentCtx, timeout);
}
/**
* Creates a derived context, which has a specific key-value pair set as well
* as all key-value pairs that were set in the original context.
*
* @param parentCtx - A parent context that shall be used as a base
* @param key - The key of the value to set
* @param value - The value, or a function that accepts the previous value (or
* undefined if not set yet) and computes the new value
* @returns A decorator that can be passed to {@link Context.use}
* @returns A new {@link Context}
*/
static setValue(
static withValue(
parentCtx: Context,
key: string,
value: unknown | ((previous: unknown | undefined) => unknown),
): ContextDecorator {
return ctx => {
const v = typeof value === 'function' ? value(ctx.value(key)) : value;
return ValueContext.forConstantValue(ctx, key, v);
};
): Context {
const v = typeof value === 'function' ? value(parentCtx.value(key)) : value;
return ValueContext.forConstantValue(parentCtx, key, v);
}
}
packages/backend-common/src/context/RootContext.test.ts
+1 -10
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@@ -14,23 +14,14 @@
* limitations under the License.
*/
import { Contexts } from './Contexts';
import { RootContext } from './RootContext';
describe('RootContext', () => {
it('returns empty values', async () => {
const ctx = new RootContext();
expect(ctx.abortSignal).toBeDefined();
expect(ctx.abortSignal.aborted).toBe(false);
expect(ctx.deadline).toBeUndefined();
expect(ctx.value('a')).toBeUndefined();
});
it('can decorate', () => {
const parent = new RootContext();
const child = parent.use(
Contexts.setValue('a', 2),
Contexts.setValue('a', 3),
);
expect(child.value('a')).toBe(3);
});
});
packages/backend-common/src/context/RootContext.ts
+18 -7
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@@ -14,21 +14,32 @@
* limitations under the License.
*/
import { AbortController } from 'node-abort-controller';
import { Context, ContextDecorator } from './types';
import { AbortSignal } from 'node-abort-controller';
import { Context } from './types';
/**
* Since the root context can never abort, and since nobody is every meant to
* dispatch events through it, we can use a static dummy instance for
* efficiency.
*/
const dummyAbortSignal: AbortSignal = Object.freeze({
aborted: false,
addEventListener() {},
removeEventListener() {},
dispatchEvent() {
return true;
},
onabort: null,
});
/**
* An empty root context.
*/
export class RootContext implements Context {
readonly abortSignal = new AbortController().signal;
readonly abortSignal = dummyAbortSignal;
readonly deadline = undefined;
value<T = unknown>(_key: string): T | undefined {
return undefined;
}
use(...items: ContextDecorator[]): Context {
return items.reduce((prev, curr) => curr(prev), this as Context);
}
}
packages/backend-common/src/context/ValueContext.test.ts
-11
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@@ -14,7 +14,6 @@
* limitations under the License.
*/
import { Contexts } from './Contexts';
import { RootContext } from './RootContext';
import { ValueContext } from './ValueContext';
@@ -42,14 +41,4 @@ describe('ValueContext', () => {
expect(d.value('b')).toBe(4);
expect(d.value('x')).toBe(2);
});
it('can decorate', () => {
const root = new RootContext();
const parent = ValueContext.forConstantValue(root, 'a', 1);
const child = parent.use(
Contexts.setValue('a', 2),
Contexts.setValue('a', 3),
);
expect(child.value('a')).toBe(3);
});
});
packages/backend-common/src/context/ValueContext.ts
+1 -5
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@@ -15,7 +15,7 @@
*/
import { AbortSignal } from 'node-abort-controller';
import { Context, ContextDecorator } from './types';
import { Context } from './types';
/**
* A context that just holds a single value, and delegates the rest to its
@@ -43,8 +43,4 @@ export class ValueContext implements Context {
value<T = unknown>(key: string): T | undefined {
return key === this._key ? (this._value as T) : this._parent.value(key);
}
use(...items: ContextDecorator[]): Context {
return items.reduce((prev, curr) => curr(prev), this as Context);
}
}
packages/backend-common/src/context/index.ts
+1 -1
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@@ -15,4 +15,4 @@
*/
export { Contexts } from './Contexts';
export type { Context, ContextDecorator } from './types';
export type { Context } from './types';
packages/backend-common/src/context/types.ts
-20
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@@ -16,14 +16,6 @@
import { AbortSignal } from 'node-abort-controller';
/**
* A function that accepts a context and produces a new, derived context from,
* decorated with some specific behavior.
*
* @public
*/
export type ContextDecorator = (ctx: Context) => Context;
/**
* A context that is meant to be passed as a ctx variable down the call chain,
* to pass along scoped information and abort signals.
@@ -50,16 +42,4 @@ export interface Context {
* @returns The associated value, or undefined if not set
*/
value<T = unknown>(key: string): T | undefined;
/**
* Decorates this context with one or more behaviors.
*
* @remarks
*
* The decorators are applied in the order that they are given.
*
* @param decorators - The decorators to apply
* @returns A derived context with the relevant behaviors
*/
use(...decorators: ContextDecorator[]): Context;
}