Check for binary file warning and don't print (#11)

* Check for binary file warning and don't print
* Fix: run ocamlformat on changes
* Improve comment + switch match to if

Author: heathhenley

lib/fs/dune

@@ -1,5 +1,6 @@
 (library
  (name fs)
  (libraries
+  str
   ;; Internal dependencies
   pretty))

lib/fs/fs.ml

@@ -7,6 +7,18 @@ type tree =
   | File of string * file_contents lazy_t
   | Dir of string * tree array
 
+(* Regex to used to determine if bat outputs a binary file warning. This is a
+   bit of a fragile approach, but there is no robust way to determine if a file
+   is binary or not. Improve this if it becomes a problem.
+*)
+let binary_file_pattern = Str.regexp ".*\\[bat warning\\].*Binary.*content*."
+let binary_file_warning = "This file is binary and cannot be displayed"
+
+let has_binary_warning contents =
+  Str.string_match binary_file_pattern contents 0
+
+(* Extracts the file name from a tree node *)
+
 let file_name = function
   | File (name, _) -> name
   | Dir (name, _) -> name
@@ -35,14 +47,16 @@ let read_file_contents path =
      --paging=never --terminal-width=80 " ^ path
   in
   let contents = Shell.proc_stdout cmd in
-  let lines =
-    contents
-    |> String.split_on_char '\n'
-    |> List.map Pretty.str
-    |> Array.of_list
-  in
-  let offset = 0 in
-  { lines; offset }
+  if has_binary_warning contents then
+    { lines = [| Pretty.str binary_file_warning |]; offset = 0 }
+  else
+    let lines =
+      contents
+      |> String.split_on_char '\n'
+      |> List.map Pretty.str
+      |> Array.of_list
+    in
+    { lines; offset = 0 }
 
 let rec to_tree path =
   if Sys.is_directory path then