Do uninstallation in steps (#138)

Fixes #122, and adds tests for it:

The problem, I believe, was that some files were deleted before their symlink was deleted. `Unix.stat` fails on symlinks that point to missing files. We don't really care about their stat, honestly, so we can just run `Unix.lstat` and remove them.

library/Fs.re

@@ -43,25 +43,39 @@ let readlink = path =>
   | err => Lwt.return_error(err)
   };
 
-// Credit: https://github.com/fastpack/fastpack/blob/9f6aa7d5b83ffef03e73a15679200576ff9dbcb7/FastpackUtil/FS.re#L94
-let rec rmdir = dir => {
-  let%lwt files = Lwt_unix.files_of_directory(dir) |> Lwt_stream.to_list;
-  let%lwt () =
-    Lwt_list.iter_s(
-      filename =>
-        switch (filename) {
-        | "."
-        | ".." => Lwt.return_unit
-        | _ =>
-          let path = Filename.concat(dir, filename);
-          switch%lwt (Lwt_unix.stat(path)) {
-          | {st_kind: Lwt_unix.S_DIR, _} => rmdir(path)
-          | _ => Lwt_unix.unlink(path)
-          };
-        },
-      files,
-    );
-  Lwt_unix.rmdir(dir);
+[@deriving show]
+type file_type =
+  | File(string)
+  | Dir(string);
+
+// Based on: https://github.com/fastpack/fastpack/blob/9f6aa7d5b83ffef03e73a15679200576ff9dbcb7/FastpackUtil/FS.re#L94
+let rec listDirRecursively = dir => {
+  switch%lwt (Lwt_unix.lstat(dir)) {
+  | {st_kind: Lwt_unix.S_DIR, _} =>
+    Lwt_unix.files_of_directory(dir)
+    |> Lwt_stream.map_list_s(
+         fun
+         | "."
+         | ".." => Lwt.return([])
+         | filename => Filename.concat(dir, filename) |> listDirRecursively,
+       )
+    |> Lwt_stream.to_list
+    |> Lwt.map(xs => List.append(xs, [Dir(dir)]))
+  | _ => Lwt.return([File(dir)])
+  | exception (Unix.Unix_error(Unix.ENOENT, _, _)) => Lwt.return([])
+  };
+};
+
+let rmdir = dir => {
+  let%lwt entities = listDirRecursively(dir);
+
+  entities
+  |> Lwt_list.map_s(
+       fun
+       | Dir(dir) => Lwt_unix.rmdir(dir)
+       | File(file) => Lwt_unix.unlink(file),
+     )
+  |> Lwt.map(_ => ());
 };
 
 type path =

test/TestFnm.re

@@ -1,4 +1,5 @@
 include SmokeTest;
 include TestSemver;
+include TestFs;
 
 TestFramework.cli();

test/TestFs.re

@@ -0,0 +1,61 @@
+open TestFramework;
+open Fnm;
+
+let get_tempdir = prefix => {
+  Printf.sprintf(
+    "fnm-test-%s-%s",
+    prefix,
+    Unix.time() |> int_of_float |> string_of_int,
+  )
+  |> Filename.concat(Filename.get_temp_dir_name());
+};
+
+describe("TestSemver", ({test, describe, _}) => {
+  describe("listDirRecursively", ({test, _}) => {
+    test("list files and directories", ({expect, _}) => {
+      let xs = Fs.listDirRecursively("feature_tests") |> Lwt_main.run;
+      expect.list(xs).toContainEqual(
+        Fs.File("feature_tests/multishell/run.sh"),
+      );
+      expect.list(xs).toContainEqual(Fs.Dir("feature_tests/multishell"));
+      expect.list(xs).toContainEqual(Fs.Dir("feature_tests"));
+    });
+
+    test("works with symlinks", ({expect, _}) => {
+      let tmpdir = get_tempdir("symlinks");
+      let fileDir = Filename.concat(tmpdir, "a/b/c/d/e/f/g");
+      let filePath = Filename.concat(fileDir, "file");
+      Sys.command("mkdir -p " ++ fileDir) |> ignore;
+      Sys.command("touch " ++ filePath) |> ignore;
+      Sys.command("ln -s " ++ filePath ++ " " ++ filePath ++ "_link")
+      |> ignore;
+      Sys.command(
+        "ln -s " ++ filePath ++ "_not_found " ++ filePath ++ "_link_not_found",
+      )
+      |> ignore;
+
+      let xs = Fs.listDirRecursively(tmpdir) |> Lwt_main.run;
+      expect.list(xs).toContainEqual(Fs.File(filePath ++ "_link"));
+      expect.list(xs).toContainEqual(
+        Fs.File(filePath ++ "_link_not_found"),
+      );
+      expect.list(xs).toContainEqual(Fs.File(filePath));
+      expect.list(xs).toContainEqual(Fs.Dir(fileDir));
+    });
+  });
+
+  test("rmdir", ({expect, _}) => {
+    let tmpdir = get_tempdir("rmdir");
+    let fileDir = Filename.concat(tmpdir, "a/b/c/d/e/f/g");
+    let filePath = Filename.concat(fileDir, "file");
+
+    Sys.command("mkdir -p " ++ fileDir) |> ignore;
+    Sys.command("touch " ++ filePath) |> ignore;
+    Unix.symlink(filePath, filePath ++ "_link");
+    Fs.rmdir(tmpdir) |> Lwt_main.run;
+
+    let remainingFiles = Fs.listDirRecursively(tmpdir) |> Lwt_main.run;
+
+    expect.list(remainingFiles).toBeEmpty();
+  });
+});