fs: support copy of relative links with cp and cpSync

Fixes: nodejs#41693

Signed-off-by: Marcos Bjoerkelund <[email protected]>

doc/api/fs.md

@@ -896,6 +896,8 @@ added: v16.7.0
   * `preserveTimestamps` {boolean} When `true` timestamps from `src` will
     be preserved. **Default:** `false`.
   * `recursive` {boolean} copy directories recursively **Default:** `false`
+  * `absolute` {boolean} convert relative symlinks to absolute symlinks.
+    **Default:** `true`
 * Returns: {Promise} Fulfills with `undefined` upon success.
 
 Asynchronously copies the entire directory structure from `src` to `dest`,
@@ -2083,6 +2085,8 @@ added: v16.7.0
   * `preserveTimestamps` {boolean} When `true` timestamps from `src` will
     be preserved. **Default:** `false`.
   * `recursive` {boolean} copy directories recursively **Default:** `false`
+  * `absolute` {boolean} convert relative symlinks to absolute symlinks.
+    **Default:** `true`
 * `callback` {Function}
 
 Asynchronously copies the entire directory structure from `src` to `dest`,
@@ -4665,6 +4669,8 @@ added: v16.7.0
   * `preserveTimestamps` {boolean} When `true` timestamps from `src` will
     be preserved. **Default:** `false`.
   * `recursive` {boolean} copy directories recursively **Default:** `false`
+  * `absolute` {boolean} convert relative symlinks to absolute symlinks.
+    **Default:** `true`
 
 Synchronously copies the entire directory structure from `src` to `dest`,
 including subdirectories and files.

lib/internal/fs/cp/cp-sync.js

@@ -182,7 +182,7 @@ function getStats(destStat, src, dest, opts) {
            srcStat.isBlockDevice()) {
     return onFile(srcStat, destStat, src, dest, opts);
   } else if (srcStat.isSymbolicLink()) {
-    return onLink(destStat, src, dest);
+    return onLink(destStat, src, dest, opts);
   } else if (srcStat.isSocket()) {
     throw new ERR_FS_CP_SOCKET({
       message: `cannot copy a socket file: ${dest}`,
@@ -293,9 +293,9 @@ function copyDir(src, dest, opts) {
   }
 }
 
-function onLink(destStat, src, dest) {
+function onLink(destStat, src, dest, opts) {
   let resolvedSrc = readlinkSync(src);
-  if (!isAbsolute(resolvedSrc)) {
+  if (opts.absolute && !isAbsolute(resolvedSrc)) {
     resolvedSrc = resolve(dirname(src), resolvedSrc);
   }
   if (!destStat) {

lib/internal/fs/cp/cp.js

@@ -222,7 +222,7 @@ async function getStatsForCopy(destStat, src, dest, opts) {
             srcStat.isBlockDevice()) {
     return onFile(srcStat, destStat, src, dest, opts);
   } else if (srcStat.isSymbolicLink()) {
-    return onLink(destStat, src, dest);
+    return onLink(destStat, src, dest, opts);
   } else if (srcStat.isSocket()) {
     throw new ERR_FS_CP_SOCKET({
       message: `cannot copy a socket file: ${dest}`,
@@ -335,9 +335,9 @@ async function copyDir(src, dest, opts) {
   }
 }
 
-async function onLink(destStat, src, dest) {
+async function onLink(destStat, src, dest, opts) {
   let resolvedSrc = await readlink(src);
-  if (!isAbsolute(resolvedSrc)) {
+  if (opts.absolute && !isAbsolute(resolvedSrc)) {
     resolvedSrc = resolve(dirname(src), resolvedSrc);
   }
   if (!destStat) {

lib/internal/fs/utils.js

@@ -724,6 +724,7 @@ const defaultCpOptions = {
   force: true,
   preserveTimestamps: false,
   recursive: false,
+  absolute: true,
 };
 
 const defaultRmOptions = {
@@ -749,6 +750,7 @@ const validateCpOptions = hideStackFrames((options) => {
   validateBoolean(options.force, 'options.force');
   validateBoolean(options.preserveTimestamps, 'options.preserveTimestamps');
   validateBoolean(options.recursive, 'options.recursive');
+  validateBoolean(options.absolute, 'options.absolute');
   if (options.filter !== undefined) {
     validateFunction(options.filter, 'options.filter');
   }

test/parallel/test-fs-cp.mjs

@@ -15,7 +15,7 @@ const {
   writeFileSync,
 } = fs;
 import net from 'net';
-import { join } from 'path';
+import { join, isAbsolute } from 'path';
 import { pathToFileURL } from 'url';
 import { setTimeout } from 'timers/promises';
 
@@ -95,6 +95,39 @@ function nextdir() {
 }
 
 
+// It resolves relative symlinks to absolute path when absolute is true
+{
+  const src = nextdir();
+  mkdirSync(src, { recursive: true });
+  writeFileSync(join(src, 'foo.js'), 'foo', 'utf8');
+  symlinkSync('foo.js', join(src, 'bar.js'));
+
+  const dest = nextdir();
+  mkdirSync(dest, { recursive: true });
+
+  cpSync(src, dest, { recursive: true, absolute: true });
+  const link = readlinkSync(join(dest, 'bar.js'));
+  assert.strictEqual(link, join(src, 'foo.js'));
+}
+
+
+// It copies relative symlink when absolute is false
+{
+  const src = nextdir();
+  mkdirSync(src, { recursive: true });
+  writeFileSync(join(src, 'foo.js'), 'foo', 'utf8');
+  symlinkSync('foo.js', join(src, 'bar.js'));
+
+  const dest = nextdir();
+  mkdirSync(dest, { recursive: true });
+  const destFile = join(dest, 'foo.js');
+
+  cpSync(src, dest, { recursive: true, absolute: false });
+  const link = readlinkSync(join(dest, 'bar.js'));
+  assert.strictEqual(link, 'foo.js');
+}
+
+
 // It throws error when src and dest are identical.
 {
   const src = './test/fixtures/copy/kitchen-sink';