1 files changed, 57 insertions, 0 deletions
diff --git a/lib/filesystem.nix b/lib/filesystem.nix
new file mode 100644
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--- /dev/null
+++ b/lib/filesystem.nix
@@ -0,0 +1,57 @@
+{ lib }:
+{ # haskellPathsInDir : Path -> Map String Path
+  # A map of all haskell packages defined in the given path,
+  # identified by having a cabal file with the same name as the
+  # directory itself.
+  haskellPathsInDir = root:
+    let # Files in the root
+        root-files = builtins.attrNames (builtins.readDir root);
+        # Files with their full paths
+        root-files-with-paths =
+          map (file:
+            { name = file; value = root + "/${file}"; }
+          ) root-files;
+        # Subdirectories of the root with a cabal file.
+        cabal-subdirs =
+          builtins.filter ({ name, value }:
+            builtins.pathExists (value + "/${name}.cabal")
+          ) root-files-with-paths;
+    in builtins.listToAttrs cabal-subdirs;
+  # locateDominatingFile :  RegExp
+  #                      -> Path
+  #                      -> Nullable { path : Path;
+  #                                    matches : [ MatchResults ];
+  #                                  }
+  # Find the first directory containing a file matching 'pattern'
+  # upward from a given 'file'.
+  # Returns 'null' if no directories contain a file matching 'pattern'.
+  locateDominatingFile = pattern: file:
+    let go = path:
+          let files = builtins.attrNames (builtins.readDir path);
+              matches = builtins.filter (match: match != null)
+                          (map (builtins.match pattern) files);
+          in
+            if builtins.length matches != 0
+              then { inherit path matches; }
+              else if path == /.
+                then null
+                else go (dirOf path);
+        parent = dirOf file;
+        isDir =
+          let base = baseNameOf file;
+              type = (builtins.readDir parent).${base} or null;
+          in file == /. || type == "directory";
+    in go (if isDir then file else parent);
+
+
+  # listFilesRecursive: Path -> [ Path ]
+  #
+  # Given a directory, return a flattened list of all files within it recursively.
+  listFilesRecursive = dir: lib.flatten (lib.mapAttrsToList (name: type:
+    if type == "directory" then
+      lib.filesystem.listFilesRecursive (dir + "/${name}")
+    else
+      dir + "/${name}"
+  ) (builtins.readDir dir));
+
+}