From 56e71f62dc49e64fcd37768cc7d1ec219d4990e6 Mon Sep 17 00:00:00 2001
From: Shea Levy <shea@shealevy.com>
Date: Sat, 4 Mar 2017 13:15:23 -0500
Subject: Add locateDominatingFile lib function

---
 lib/filesystem.nix | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)
 create mode 100644 lib/filesystem.nix

(limited to 'lib/filesystem.nix')

diff --git a/lib/filesystem.nix b/lib/filesystem.nix
new file mode 100644
index 0000000000000..91b04d81c13be
--- /dev/null
+++ b/lib/filesystem.nix
@@ -0,0 +1,26 @@
+{ # 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);
+}
-- 
cgit 1.4.1