Add --no-dependents option to output modules without dependents

- Introduced a new command-line flag `--no-dependents` and its shorthand `-nd` to filter output for modules that have no dependents.
- Implemented functionality in the formatter to handle output in both DOT and JSON formats for modules without dependents.
- Added a helper function to identify modules with no dependents in the dependency graph.

Author: mununki

bin/main.ml

@@ -8,6 +8,7 @@ let verbose = ref false
 let benchmark = ref false
 let skip_cache = ref false
 let clear_cache = ref false
+let no_dependents = ref false
 
 let spec_list =
   [
@@ -51,6 +52,12 @@ let spec_list =
     ( "--clear-cache",
       Arg.Set clear_cache,
       "Clear the in-memory cache before analyzing" );
+    ( "--no-dependents",
+      Arg.Set no_dependents,
+      "Output modules with no dependents" );
+    ( "-nd",
+      Arg.Set no_dependents,
+      "Output modules with no dependents (short for --no-dependents)" );
   ]
 
 let anon_fun file = input_files := file :: !input_files
@@ -142,12 +149,19 @@ let main () =
         (* Output to file only *)
         if !verbose then Printf.eprintf "Writing output to file: %s\n" file;
         let out_channel = open_out file in
-        Rescriptdep.Formatter.output_graph !format focused_graph out_channel;
+        if !no_dependents then
+          Rescriptdep.Formatter.output_no_dependents !format focused_graph
+            out_channel
+        else
+          Rescriptdep.Formatter.output_graph !format focused_graph out_channel;
         close_out out_channel
     | None ->
         (* Output to stdout when no file output option is provided *)
         if !verbose then Printf.eprintf "Writing output to stdout\n";
-        Rescriptdep.Formatter.output_graph !format focused_graph stdout);
+        if !no_dependents then
+          Rescriptdep.Formatter.output_no_dependents !format focused_graph
+            stdout
+        else Rescriptdep.Formatter.output_graph !format focused_graph stdout);
 
     let output_end_time = Unix.gettimeofday () in
     let output_time = output_end_time -. output_start_time in

lib/dependency_graph.ml

@@ -330,3 +330,8 @@ let create_focused_graph graph center_module =
     in
 
     result
+
+(* Find modules with no dependents *)
+let find_modules_with_no_dependents graph =
+  let modules = get_modules graph in
+  List.filter (fun m -> find_dependents graph m = []) modules

lib/formatter.ml

@@ -421,6 +421,26 @@ and output_json graph out_channel =
   (* JSON closing *)
   output_string out_channel "}\n"
 
+(* Output modules with no dependents *)
+let output_no_dependents_dot modules out_channel =
+  output_string out_channel "digraph G {\n";
+  output_string out_channel "  rankdir=LR;\n";
+  output_string out_channel "  node [shape=box];\n";
+  List.iter
+    (fun m -> output_string out_channel (Printf.sprintf "  \"%s\";\n" m))
+    modules;
+  output_string out_channel "}\n"
+
+let output_no_dependents_json modules out_channel =
+  let json = `List (List.map (fun m -> `String m) modules) in
+  Yojson.Basic.pretty_to_channel out_channel json
+
+let output_no_dependents format graph out_channel =
+  let modules = Dependency_graph.find_modules_with_no_dependents graph in
+  match format with
+  | Dot -> output_no_dependents_dot modules out_channel
+  | Json -> output_no_dependents_json modules out_channel
+
 (* String representation of a format *)
 let format_to_string = function Dot -> "dot" | Json -> "json"