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/**
* Copyright 2023 Google Inc. All rights reserved.
*
* 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.
*/
const createdFunctions = new Map<string, (...args: unknown[]) => unknown>();
/**
* Creates a function from a string.
*
* @internal
*/
export const createFunction = (
functionValue: string
): ((...args: unknown[]) => unknown) => {
let fn = createdFunctions.get(functionValue);
if (fn) {
return fn;
}
fn = new Function(`return ${functionValue}`)() as (
...args: unknown[]
) => unknown;
createdFunctions.set(functionValue, fn);
return fn;
};
/**
* @internal
*/
export function stringifyFunction(fn: (...args: never) => unknown): string {
let value = fn.toString();
try {
new Function(`(${value})`);
} catch {
// This means we might have a function shorthand (e.g. `test(){}`). Let's
// try prefixing.
let prefix = 'function ';
if (value.startsWith('async ')) {
prefix = `async ${prefix}`;
value = value.substring('async '.length);
}
value = `${prefix}${value}`;
try {
new Function(`(${value})`);
} catch {
// We tried hard to serialize, but there's a weird beast here.
throw new Error('Passed function cannot be serialized!');
}
}
return value;
}
/**
* Replaces `PLACEHOLDER`s with the given replacements.
*
* All replacements must be valid JS code.
*
* @example
*
* ```ts
* interpolateFunction(() => PLACEHOLDER('test'), {test: 'void 0'});
* // Equivalent to () => void 0
* ```
*
* @internal
*/
export const interpolateFunction = <T extends (...args: never[]) => unknown>(
fn: T,
replacements: Record<string, string>
): T => {
let value = stringifyFunction(fn);
for (const [name, jsValue] of Object.entries(replacements)) {
value = value.replace(
new RegExp(`PLACEHOLDER\\(\\s*(?:'${name}'|"${name}")\\s*\\)`, 'g'),
jsValue
);
}
return createFunction(value) as unknown as T;
};
declare global {
/**
* Used for interpolation with {@link interpolateFunction}.
*
* @internal
*/
function PLACEHOLDER<T>(name: string): T;
}
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