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/**
* @license
* Copyright 2025 Google LLC
* SPDX-License-Identifier: Apache-2.0
*/
/**
* Resolves environment variables in a string.
* Replaces $VAR_NAME and ${VAR_NAME} with their corresponding environment variable values.
* If the environment variable is not defined, the original placeholder is preserved.
*
* @param value - The string that may contain environment variable placeholders
* @returns The string with environment variables resolved
*
* @example
* resolveEnvVarsInString("Token: $API_KEY") // Returns "Token: secret-123"
* resolveEnvVarsInString("URL: ${BASE_URL}/api") // Returns "URL: https://api.example.com/api"
* resolveEnvVarsInString("Missing: $UNDEFINED_VAR") // Returns "Missing: $UNDEFINED_VAR"
*/
export function resolveEnvVarsInString(value: string): string {
const envVarRegex = /\$(?:(\w+)|{([^}]+)})/g; // Find $VAR_NAME or ${VAR_NAME}
return value.replace(envVarRegex, (match, varName1, varName2) => {
const varName = varName1 || varName2;
if (process && process.env && typeof process.env[varName] === 'string') {
return process.env[varName]!;
}
return match;
});
}
/**
* Recursively resolves environment variables in an object of any type.
* Handles strings, arrays, nested objects, and preserves other primitive types.
* Protected against circular references using a WeakSet to track visited objects.
*
* @param obj - The object to process for environment variable resolution
* @returns A new object with environment variables resolved
*
* @example
* const config = {
* server: {
* host: "$HOST",
* port: "${PORT}",
* enabled: true,
* tags: ["$ENV", "api"]
* }
* };
* const resolved = resolveEnvVarsInObject(config);
*/
export function resolveEnvVarsInObject<T>(obj: T): T {
return resolveEnvVarsInObjectInternal(obj, new WeakSet());
}
/**
* Internal implementation of resolveEnvVarsInObject with circular reference protection.
*
* @param obj - The object to process
* @param visited - WeakSet to track visited objects and prevent circular references
* @returns A new object with environment variables resolved
*/
function resolveEnvVarsInObjectInternal<T>(
obj: T,
visited: WeakSet<object>,
): T {
if (
obj === null ||
obj === undefined ||
typeof obj === 'boolean' ||
typeof obj === 'number'
) {
return obj;
}
if (typeof obj === 'string') {
return resolveEnvVarsInString(obj) as unknown as T;
}
if (Array.isArray(obj)) {
// Check for circular reference
if (visited.has(obj)) {
// Return a shallow copy to break the cycle
return [...obj] as unknown as T;
}
visited.add(obj);
const result = obj.map((item) =>
resolveEnvVarsInObjectInternal(item, visited),
) as unknown as T;
visited.delete(obj);
return result;
}
if (typeof obj === 'object') {
// Check for circular reference
if (visited.has(obj as object)) {
// Return a shallow copy to break the cycle
return { ...obj } as T;
}
visited.add(obj as object);
const newObj = { ...obj } as T;
for (const key in newObj) {
if (Object.prototype.hasOwnProperty.call(newObj, key)) {
newObj[key] = resolveEnvVarsInObjectInternal(newObj[key], visited);
}
}
visited.delete(obj as object);
return newObj;
}
return obj;
}
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