stdlib/os: handle symlinks in copy/move functions (#16709)

* stdlib/os: handle symlinks in copy/move functions

- Added optional `options` argument to `copyFile`, `copyFileToDir`, and
  `copyFileWithPermissions`. By default, symlinks are followed (copy files
  symlinks point to).
- `copyDir` and `copyDirWithPermissions` copy symlinks as symlinks (instead of
  skipping them as it was before).
- `moveFile` and `moveDir` move symlinks as symlinks (instead of skipping them
  sometimes as it was before).
- Added optional `followSymlinks` argument to `setFilePermissions`.

See also: https://github.com/nim-lang/RFCs/issues/319

Co-authored-by: Timothee Cour <timothee.cour2@gmail.com>

* Address comments in #16709

Co-authored-by: Timothee Cour <timothee.cour2@gmail.com>

* Address comments in #16709 (second iteration)

Skip symlinks on Windows.

Co-authored-by: Timothee Cour <timothee.cour2@gmail.com>

1 files changed, 107 insertions, 0 deletions

diff --git a/tests/stdlib/tos.nim b/tests/stdlib/tos.nim
index af3606a4a..b47412a62 100644
--- a/tests/stdlib/tos.nim
+++ b/tests/stdlib/tos.nim
@@ -26,6 +26,7 @@ Raises
 # test os path creation, iteration, and deletion
 
 import os, strutils, pathnorm
+from stdtest/specialpaths import buildDir
 
 block fileOperations:
   let files = @["these.txt", "are.x", "testing.r", "files.q"]
@@ -154,6 +155,112 @@ block fileOperations:
   doAssert fileExists("../dest/a/file.txt")
   removeDir("../dest")
 
+  # Symlink handling in `copyFile`, `copyFileWithPermissions`, `copyFileToDir`,
+  # `copyDir`, `copyDirWithPermissions`, `moveFile`, and `moveDir`.
+  block:
+    const symlinksAreHandled = not defined(windows)
+    const dname = buildDir/"D20210116T140629"
+    const subDir = dname/"sub"
+    const subDir2 = dname/"sub2"
+    const brokenSymlinkName = "D20210101T191320_BROKEN_SYMLINK"
+    const brokenSymlink = dname/brokenSymlinkName
+    const brokenSymlinkSrc = "D20210101T191320_nonexistant"
+    const brokenSymlinkCopy = brokenSymlink & "_COPY"
+    const brokenSymlinkInSubDir = subDir/brokenSymlinkName
+    const brokenSymlinkInSubDir2 = subDir2/brokenSymlinkName
+
+    createDir(subDir)
+    createSymlink(brokenSymlinkSrc, brokenSymlink)
+
+    # Test copyFile
+    when symlinksAreHandled:
+      doAssertRaises(OSError):
+        copyFile(brokenSymlink, brokenSymlinkCopy)
+      doAssertRaises(OSError):
+        copyFile(brokenSymlink, brokenSymlinkCopy, {cfSymlinkFollow})
+    copyFile(brokenSymlink, brokenSymlinkCopy, {cfSymlinkIgnore})
+    doAssert not fileExists(brokenSymlinkCopy)
+    copyFile(brokenSymlink, brokenSymlinkCopy, {cfSymlinkAsIs})
+    when symlinksAreHandled:
+      doAssert expandSymlink(brokenSymlinkCopy) == brokenSymlinkSrc
+      removeFile(brokenSymlinkCopy)
+    else:
+      doAssert not fileExists(brokenSymlinkCopy)
+    doAssertRaises(AssertionDefect):
+      copyFile(brokenSymlink, brokenSymlinkCopy,
+               {cfSymlinkAsIs, cfSymlinkFollow})
+
+    # Test copyFileWithPermissions
+    when symlinksAreHandled:
+      doAssertRaises(OSError):
+        copyFileWithPermissions(brokenSymlink, brokenSymlinkCopy)
+      doAssertRaises(OSError):
+        copyFileWithPermissions(brokenSymlink, brokenSymlinkCopy,
+                                options = {cfSymlinkFollow})
+    copyFileWithPermissions(brokenSymlink, brokenSymlinkCopy,
+                            options = {cfSymlinkIgnore})
+    doAssert not fileExists(brokenSymlinkCopy)
+    copyFileWithPermissions(brokenSymlink, brokenSymlinkCopy,
+                            options = {cfSymlinkAsIs})
+    when symlinksAreHandled:
+      doAssert expandSymlink(brokenSymlinkCopy) == brokenSymlinkSrc
+      removeFile(brokenSymlinkCopy)
+    else:
+      doAssert not fileExists(brokenSymlinkCopy)
+    doAssertRaises(AssertionDefect):
+      copyFileWithPermissions(brokenSymlink, brokenSymlinkCopy,
+                              options = {cfSymlinkAsIs, cfSymlinkFollow})
+
+    # Test copyFileToDir
+    when symlinksAreHandled:
+      doAssertRaises(OSError):
+        copyFileToDir(brokenSymlink, subDir)
+      doAssertRaises(OSError):
+        copyFileToDir(brokenSymlink, subDir, {cfSymlinkFollow})
+    copyFileToDir(brokenSymlink, subDir, {cfSymlinkIgnore})
+    doAssert not fileExists(brokenSymlinkInSubDir)
+    copyFileToDir(brokenSymlink, subDir, {cfSymlinkAsIs})
+    when symlinksAreHandled:
+      doAssert expandSymlink(brokenSymlinkInSubDir) == brokenSymlinkSrc
+      removeFile(brokenSymlinkInSubDir)
+    else:
+      doAssert not fileExists(brokenSymlinkInSubDir)
+
+    createSymlink(brokenSymlinkSrc, brokenSymlinkInSubDir)
+
+    # Test copyDir
+    copyDir(subDir, subDir2)
+    when symlinksAreHandled:
+      doAssert expandSymlink(brokenSymlinkInSubDir2) == brokenSymlinkSrc
+    else:
+      doAssert not fileExists(brokenSymlinkInSubDir2)
+    removeDir(subDir2)
+
+    # Test copyDirWithPermissions
+    copyDirWithPermissions(subDir, subDir2)
+    when symlinksAreHandled:
+      doAssert expandSymlink(brokenSymlinkInSubDir2) == brokenSymlinkSrc
+    else:
+      doAssert not fileExists(brokenSymlinkInSubDir2)
+    removeDir(subDir2)
+
+    # Test moveFile
+    moveFile(brokenSymlink, brokenSymlinkCopy)
+    when not defined(windows):
+      doAssert expandSymlink(brokenSymlinkCopy) == brokenSymlinkSrc
+    else:
+      doAssert symlinkExists(brokenSymlinkCopy)
+    removeFile(brokenSymlinkCopy)
+
+    # Test moveDir
+    moveDir(subDir, subDir2)
+    when not defined(windows):
+      doAssert expandSymlink(brokenSymlinkInSubDir2) == brokenSymlinkSrc
+    else:
+      doAssert symlinkExists(brokenSymlinkInSubDir2)
+
+    removeDir(dname)
+
 import times
 block modificationTime:
   # Test get/set modification times