cp_r function does not preserve symlinks (unlike cp -r) in copied directory

[mwu-tow]

Using Shelly on Linux this time. I have a directory containing a symlink with relative path. If I copy the directory using the cp_r function, it replaces the symlinks with the target files. If I run cp -r command the target directory has symlinks preserved.

Shouldn't cp_r and cp -r do the same things? That's what I'd expect.

[gregwebs]

This does seem like nicer default behavior.

Right now I am doing my own descent and using this copyFile function.

sytem-fileio is deprecated now, but I would assume that the behavior from directory is the same.

So it seems like the easiest thing to do is to just insert a symlink check. Interested in adding a test case to Shelly for this?

[mwu-tow]

I'm not sure how this should be best approached as the test would be platform specific and would require adding such dependency as unix package.

[gregwebs]

Can always use conditional compilation for Windows. Maybe there is a library that already implements cp -r cross-platform that can be used?

[kgadek]

Making a test case without unix is difficult as well. Symlinks on Windows are rather tricky, they requires admin rights to create them. Bloody hackers and their symlinks!.

Anyway, here is a draft for the test: symlinks with absolute paths.

However, this fails – surprisingly for me – with Exception: FilePath "/Users/foo/bar/baz/shelly/test/a/d1": createSymbolicLink: does not exist (No such file or directory)).

diff --git a/shelly.cabal b/shelly.cabal
index be228a5..a27272b 100644
--- a/shelly.cabal
+++ b/shelly.cabal
@@ -137,7 +137,8 @@ Test-Suite shelly-testsuite
     lifted-base,
     lifted-async,
     enclosed-exceptions,
-    exceptions
+    exceptions,
+    unix

   extensions:
     CPP
diff --git a/test/src/CopySpec.hs b/test/src/CopySpec.hs
index c601c22..9b92b45 100644
--- a/test/src/CopySpec.hs
+++ b/test/src/CopySpec.hs
@@ -10,6 +10,7 @@ import Prelude hiding ( FilePath)
 #endif
 import Control.Monad (forM_)
 import System.IO.Error
+import System.Posix.Files (createSymbolicLink, readSymbolicLink, fileExist, isSymbolicLink)
 import Help

 copySpec :: Spec
@@ -83,3 +84,32 @@ copySpec = do
           writefile "b/d" ""
           cp_r b b `catch_sh` (\e -> liftIO $ assert $ isUserError e)
       assert True
+
+    it "copies the symlinks" $ do
+      shelly $
+        within_dir "test/a" $ do
+
+          d1       <- absPath "d1"
+          writefile d1 ""
+          b_d2     <- absPath "b/d2"
+          b_e1     <- absPath "b/e1"
+          b_e2     <- absPath "b/e2"
+          c_cc_e1  <- absPath "c/cc/e1"
+          c_cc_e2  <- absPath "c/cc/e2"
+
+          mkdir b
+          writefile b_d2 ""
+
+          liftIO $ do
+            createSymbolicLink (show d1) (show b_e1)
+            createSymbolicLink (show b_d2) (show b_e2)
+
+          mkdir_p c
+          cp_r b "c/cc"
+
+          e1_res <- liftIO $ readSymbolicLink (show c_cc_e1)
+          e2_res <- liftIO $ readSymbolicLink (show c_cc_e2)
+
+          liftIO $ assert $ e1_res == (show d1)
+          liftIO $ assert $ e2_res == (show b_d2)
+      assert True

Probably we could make this test-case and requirement on unix conditional.

As for library with cp -r functionality: I'm not aware of any.