mergeConfigRecursively() — astro Function Reference

Architecture documentation for the mergeConfigRecursively() function in merge.ts from the astro codebase.

Function typescript CoreAstro RenderingEngine called by 1

Entity Profile

CoreAstro→ RenderingEngine→ mergeConfigRecursively() — astro Function Reference

Dependency Diagram

graph TD
  3e40db17_0001_3ecb_3f8e_3ef4971790f6["mergeConfigRecursively()"]
  59d6cf60_ff4d_d499_5395_b2c915d5ed58["merge.ts"]
  3e40db17_0001_3ecb_3f8e_3ef4971790f6 -->|defined in| 59d6cf60_ff4d_d499_5395_b2c915d5ed58
  4c00ca19_2bc9_05c7_bd27_7e949188bd23["mergeConfig()"]
  4c00ca19_2bc9_05c7_bd27_7e949188bd23 -->|calls| 3e40db17_0001_3ecb_3f8e_3ef4971790f6
  style 3e40db17_0001_3ecb_3f8e_3ef4971790f6 fill:#6366f1,stroke:#818cf8,color:#fff

Relationship Graph

Source Code

packages/astro/src/core/config/merge.ts lines 6–64

function mergeConfigRecursively(
	defaults: Record<string, any>,
	overrides: Record<string, any>,
	rootPath: string,
) {
	const merged: Record<string, any> = { ...defaults };
	for (const key in overrides) {
		const value = overrides[key];
		if (value == null) {
			continue;
		}

		const existing = merged[key];

		if (existing == null) {
			merged[key] = value;
			continue;
		}

		// fields that require special handling:
		if (key === 'vite' && rootPath === '') {
			merged[key] = mergeViteConfig(existing, value);
			continue;
		}
		if (key === 'server' && rootPath === '') {
			// server config can be a function or an object, if one of the two values is a function,
			// create a new wrapper function that merges them
			if (typeof existing === 'function' || typeof value === 'function') {
				merged[key] = (...args: any[]) => {
					const existingConfig = typeof existing === 'function' ? existing(...args) : existing;
					const valueConfig = typeof value === 'function' ? value(...args) : value;
					return mergeConfigRecursively(existingConfig, valueConfig, key);
				};
				continue;
			}
		}

		// for server.allowedHosts, if the value is a boolean
		if (key === 'allowedHosts' && rootPath === 'server' && typeof existing === 'boolean') {
			continue;
		}

		if (Array.isArray(existing) || Array.isArray(value)) {
			merged[key] = [...arraify(existing ?? []), ...arraify(value ?? [])];
			continue;
		}
		if (isURL(existing) && isURL(value)) {
			merged[key] = value;
			continue;
		}
		if (isObject(existing) && isObject(value)) {
			merged[key] = mergeConfigRecursively(existing, value, rootPath ? `${rootPath}.${key}` : key);
			continue;
		}

		merged[key] = value;
	}
	return merged;
}