@nestjs/cli/lib/compiler/helpers/get-effective-root-dir.js

Nest - modern, fast, powerful node.js web framework (@cli)

import { dirname, isAbsolute, normalize, resolve, sep } from 'path';
/**
 * Computes the effective TypeScript rootDir for an emit, mirroring how the
 * TypeScript compiler determines it when `rootDir` is not set in tsconfig.
 *
 * When `rootDir` is explicitly configured, its absolute, normalized form is
 * returned. Otherwise the longest common parent directory of the input file
 * list is used (the same heuristic TypeScript applies through
 * `Program#getCommonSourceDirectory`).
 *
 * Returns `undefined` if no rootDir can be determined (e.g. no input files).
 *
 * @param explicitRootDir Value of `compilerOptions.rootDir` from tsconfig, if any.
 * @param fileNames List of TypeScript input files (absolute paths).
 * @param cwd Current working directory used to resolve relative paths.
 */
export function getEffectiveRootDir(explicitRootDir, fileNames, cwd = process.cwd()) {
    if (explicitRootDir) {
        return normalize(isAbsolute(explicitRootDir)
            ? explicitRootDir
            : resolve(cwd, explicitRootDir));
    }
    if (!fileNames || fileNames.length === 0) {
        return undefined;
    }
    // Declaration files are excluded from the common source directory, matching
    // TypeScript: they produce no emit, so a `typings/**/*.d.ts` entry outside
    // `src` must not drag the computed root up to the project root and push
    // every copied asset into a `dist/src` subdirectory.
    const emittedFiles = fileNames.filter((file) => !isDeclarationFileName(file));
    if (emittedFiles.length === 0) {
        return undefined;
    }
    const absolutePaths = emittedFiles.map((file) => normalize(isAbsolute(file) ? file : resolve(cwd, file)));
    let commonDir = dirname(absolutePaths[0]);
    for (let i = 1; i < absolutePaths.length; i++) {
        commonDir = commonParentDir(commonDir, dirname(absolutePaths[i]));
        if (!commonDir) {
            return undefined;
        }
    }
    return commonDir;
}
function isDeclarationFileName(fileName) {
    return /\.d\.[cm]?ts$/i.test(fileName);
}
function commonParentDir(a, b) {
    const aSegments = a.split(sep);
    const bSegments = b.split(sep);
    const length = Math.min(aSegments.length, bSegments.length);
    let i = 0;
    while (i < length && aSegments[i] === bSegments[i]) {
        i++;
    }
    return aSegments.slice(0, i).join(sep);
}