#15 added basic tsconfig extends support

index.ts

@@ -1,139 +1,199 @@
-import { join } from 'path';
+import path from 'path';
 import { Plugin } from 'rollup';
 import {
-	CompilerOptions,
-	findConfigFile,
-	nodeModuleNameResolver,
-	parseConfigFileTextToJson,
-	sys,
+  CompilerOptions,
+  findConfigFile,
+  nodeModuleNameResolver,
+  parseConfigFileTextToJson,
+  sys,
 } from 'typescript';
 
 export const typescriptPaths = ({
-	absolute = true,
-	nonRelative = false,
-	preserveExtensions = false,
-	tsConfigPath = findConfigFile('./', sys.fileExists),
-	transform,
+  absolute = true,
+  nonRelative = false,
+  preserveExtensions = false,
+  tsConfigPath = findConfigFile('./', sys.fileExists),
+  transform,
 }: Options = {}): Plugin => {
-	const { compilerOptions, outDir } = getTsConfig(tsConfigPath);
-
-	return {
-		name: 'resolve-typescript-paths',
-		resolveId: (importee: string, importer?: string) => {
-			const enabled = Boolean(
-				compilerOptions.paths || (compilerOptions.baseUrl && nonRelative),
-			);
-
-			if (
-				typeof importer === 'undefined' ||
-				importee.startsWith('\0') ||
-				!enabled
-			) {
-				return null;
-			}
-
-			const hasMatchingPath =
-				!!compilerOptions.paths &&
-				Object.keys(compilerOptions.paths).some((path) =>
-					new RegExp('^' + path.replace('*', '.+') + '$').test(importee),
-				);
-
-			if (!hasMatchingPath && !nonRelative) {
-				return null;
-			}
-
-			if (importee.startsWith('.')) {
-				return null; // never resolve relative modules, only non-relative
-			}
-
-			const { resolvedModule } = nodeModuleNameResolver(
-				importee,
-				importer,
-				compilerOptions,
-				sys,
-			);
-
-			if (!resolvedModule) {
-				return null;
-			}
-
-			const { resolvedFileName } = resolvedModule;
-
-			if (!resolvedFileName || resolvedFileName.endsWith('.d.ts')) {
-				return null;
-			}
-
-			const targetFileName = join(
-				outDir,
-				preserveExtensions
-					? resolvedFileName
-					: resolvedFileName.replace(/\.tsx?$/i, '.js'),
-			);
-
-			const resolved = absolute
-				? sys.resolvePath(targetFileName)
-				: targetFileName;
-
-			return transform ? transform(resolved) : resolved;
-		},
-	};
+  const { compilerOptions } = getTsConfig(tsConfigPath);
+  const outDir = compilerOptions.outDir ?? '.';
+
+  return {
+    name: 'resolve-typescript-paths',
+    resolveId: (importee: string, importer?: string) => {
+      const enabled = Boolean(
+        compilerOptions.paths || (compilerOptions.baseUrl && nonRelative)
+      );
+
+      if (
+        typeof importer === 'undefined' ||
+        importee.startsWith('\0') ||
+        !enabled
+      ) {
+        return null;
+      }
+
+      const hasMatchingPath =
+        !!compilerOptions.paths &&
+        Object.keys(compilerOptions.paths).some((path) =>
+          new RegExp('^' + path.replace('*', '.+') + '$').test(importee)
+        );
+
+      if (!hasMatchingPath && !nonRelative) {
+        return null;
+      }
+
+      if (importee.startsWith('.')) {
+        return null; // never resolve relative modules, only non-relative
+      }
+
+      const { resolvedModule } = nodeModuleNameResolver(
+        importee,
+        importer,
+        compilerOptions,
+        sys
+      );
+
+      if (!resolvedModule) {
+        return null;
+      }
+
+      const { resolvedFileName } = resolvedModule;
+
+      if (!resolvedFileName || resolvedFileName.endsWith('.d.ts')) {
+        return null;
+      }
+
+      const targetFileName = path.join(
+        outDir,
+        preserveExtensions
+          ? resolvedFileName
+          : resolvedFileName.replace(/\.tsx?$/i, '.js')
+      );
+
+      const resolved = absolute
+        ? sys.resolvePath(targetFileName)
+        : targetFileName;
+
+      return transform ? transform(resolved) : resolved;
+    },
+  };
 };
 
 const getTsConfig = (configPath?: string): TsConfig => {
-	const defaults: TsConfig = { compilerOptions: {}, outDir: '.' };
-
-	if (!configPath) {
-		return defaults;
-	}
-
-	const configJson = sys.readFile(configPath);
-
-	if (!configJson) {
-		return defaults;
-	}
-
-	const { config } = parseConfigFileTextToJson(configPath, configJson);
+  const defaults: TsConfig = { compilerOptions: { outDir: '.' } };
+  if (typeof configPath !== 'string') {
+    return defaults;
+  }
+
+  // Read in tsconfig.json
+  const configJson = sys.readFile(configPath);
+  if (configJson == null) {
+    return defaults;
+  }
+
+  const { config: rootConfig } = parseConfigFileTextToJson(
+    configPath,
+    configJson
+  );
+  const rootConfigWithDefaults = {
+    ...rootConfig,
+    ...defaults,
+    compilerOptions: {
+      ...defaults.compilerOptions,
+      ...(rootConfig.compilerOptions ?? {}),
+    },
+  };
+  const resolvedConfig = handleTsConfigExtends(
+    rootConfigWithDefaults,
+    configPath
+  );
+
+  return resolvedConfig;
+};
 
-	return { ...defaults, ...config };
+const handleTsConfigExtends = (
+  config: TsConfig,
+  rootConfigPath: string
+): TsConfig => {
+  if (!('extends' in config) || typeof config.extends !== 'string') {
+    return config;
+  }
+
+  let extendedConfigPath;
+  try {
+    // Try to resolve as a module (npm)
+    extendedConfigPath = require.resolve(config.extends);
+  } catch (e) {
+    // Try to resolve as a file relative to the current config
+    extendedConfigPath = path.join(
+      path.dirname(rootConfigPath),
+      config.extends
+    );
+  }
+
+  // Read in extended tsconfig.json
+  const extendedConfig = getTsConfig(extendedConfigPath);
+
+  // Merge base config and current config.
+  // This does not handle array concatenation or nested objects,
+  // besides 'compilerOptions' paths as the other options are not relevant
+  config = {
+    ...extendedConfig,
+    ...config,
+    compilerOptions: {
+      ...extendedConfig.compilerOptions,
+      ...config.compilerOptions,
+      paths: {
+        ...(extendedConfig.compilerOptions.paths ?? {}),
+        ...(config.compilerOptions.paths ?? {}),
+      },
+    },
+  };
+
+  // Remove the "extends" field
+  delete config.extends;
+
+  return config;
 };
 
 export interface Options {
-	/**
-	 * Whether to resolve to absolute paths; defaults to `true`.
-	 */
-	absolute?: boolean;
-
-	/**
-	 * Whether to resolve non-relative paths based on tsconfig's `baseUrl`, even
-	 * if none of the `paths` are matched; defaults to `false`.
-	 *
-	 * @see https://www.typescriptlang.org/docs/handbook/module-resolution.html#relative-vs-non-relative-module-imports
-	 * @see https://www.typescriptlang.org/docs/handbook/module-resolution.html#base-url
-	 */
-	nonRelative?: boolean;
-
-	/**
-	 * Whether to preserve `.ts` and `.tsx` file extensions instead of having them
-	 * changed to `.js`; defaults to `false`.
-	 */
-	preserveExtensions?: boolean;
-
-	/**
-	 * Custom path to your `tsconfig.json`. Use this if the plugin can't seem to
-	 * find the correct one by itself.
-	 */
-	tsConfigPath?: string;
-
-	/**
-	 * If the plugin successfully resolves a path, this function allows you to
-	 * hook into the process and transform that path before it is returned.
-	 */
-	transform?(path: string): string;
+  /**
+   * Whether to resolve to absolute paths; defaults to `true`.
+   */
+  absolute?: boolean;
+
+  /**
+   * Whether to resolve non-relative paths based on tsconfig's `baseUrl`, even
+   * if none of the `paths` are matched; defaults to `false`.
+   *
+   * @see https://www.typescriptlang.org/docs/handbook/module-resolution.html#relative-vs-non-relative-module-imports
+   * @see https://www.typescriptlang.org/docs/handbook/module-resolution.html#base-url
+   */
+  nonRelative?: boolean;
+
+  /**
+   * Whether to preserve `.ts` and `.tsx` file extensions instead of having them
+   * changed to `.js`; defaults to `false`.
+   */
+  preserveExtensions?: boolean;
+
+  /**
+   * Custom path to your `tsconfig.json`. Use this if the plugin can't seem to
+   * find the correct one by itself.
+   */
+  tsConfigPath?: string;
+
+  /**
+   * If the plugin successfully resolves a path, this function allows you to
+   * hook into the process and transform that path before it is returned.
+   */
+  transform?(path: string): string;
 }
 
 interface TsConfig {
-	compilerOptions: CompilerOptions;
-	outDir: string;
+  compilerOptions: CompilerOptions;
+  extends?: string;
 }
 
 /**