NativeScript/packages/core/module-name-resolver/index.ts

import { Screen, Device } from '../platform';
import { PlatformContext, findMatch, stripQualifiers } from './qualifier-matcher';
import { Trace } from '../trace';
import { ModuleNameResolverType, ModuleListProvider, initAppForModuleResolver, getResolveInstance, _setResolver } from './helpers';

export type { PlatformContext } from './qualifier-matcher';

export class ModuleNameResolver implements ModuleNameResolverType {
	private _cache = {};

	constructor(
		private context: PlatformContext,
		private moduleListProvider: ModuleListProvider = global.getRegisteredModules,
	) {
		initAppForModuleResolver();
	}

	public resolveModuleName(path: string, ext: string): string {
		const key = path + ext;
		let result: string = this._cache[key];
		if (result === undefined) {
			result = this.resolveModuleNameImpl(path, ext);
			this._cache[key] = result;
		}

		if (Trace.isEnabled()) {
			Trace.write(`path: '${path}' with ext: '${ext}' resolved: '${result}'`, Trace.categories.ModuleNameResolver);
		}

		return result;
	}

	public clearCache(): void {
		this._cache = {};
	}

	private resolveModuleNameImpl(path: string, ext: string): string {
		let result: string = null;
		ext = ext ? '.' + ext : '';

		// This call will return a clean path without qualifiers
		path = stripQualifiers(path);

		const candidates = this.getCandidates(path, ext);
		result = findMatch(path, ext, candidates, this.context);
		return result;
	}

	private getCandidates(path: string, ext: string): Array<string> {
		const candidates = this.moduleListProvider().filter((moduleName) => moduleName.startsWith(path) && (!ext || moduleName.endsWith(ext)));
		return candidates;
	}
}

export function resolveModuleName(path: string, ext: string): string {
	if (global.__snapshot) {
		return resolveModuleSnapshot(path, ext);
	}

	if (!getResolveInstance()) {
		_setResolver(
			new ModuleNameResolver({
				width: Screen.mainScreen.widthDIPs,
				height: Screen.mainScreen.heightDIPs,
				os: Device.os,
				deviceType: Device.deviceType,
			}),
		);
	}

	return getResolveInstance().resolveModuleName(path, ext);
}

function resolveModuleSnapshot(path, ext) {
	Trace.write(`Resolving module in SNAPSHOT context - path: '${path}' with ext: '${ext}'`, Trace.categories.ModuleNameResolver);

	// Platform module when in snapshot. So resolve modules with default android phone.
	// NB: The only module name that should ever be resolved while in snapshot is app.css, because it is
	// applied explicitly in the snapshot by [NativeScriptSnapshotPlugin](https://github.com/NativeScript/nativescript-dev-webpack/blob/48b26f412fd70c19dc0b9c7763e08e9505a0ae11/plugins/NativeScriptSnapshotPlugin/index.js#L48-L56)
	return new ModuleNameResolver({
		width: 400,
		height: 800,
		os: 'Android',
		deviceType: 'Phone',
	}).resolveModuleName(path, ext);
}