Added --echo-errors.

TODO

-* If we keep --on-error-reduce, document it.
-
 * Is it true that the warning "this production is never reduced" is
   sound but incomplete? i.e. certain states could be unreachable and
   we do not know it (but LRijkstra can tell us).
@@ -15,29 +13,17 @@
 
 * Error.signal should call error_message?
 
-* Document --list-errors --interpret-error --compile-errors --compare-errors --update-errors
+* Document --list-errors --interpret-error --compile-errors --compare-errors --update-errors --echo-errors --on-error-reduce
     explain that any production that contains [error] is ignored by --list-errors
-  Should --list-errors also print the sentence in concrete form? (as a comment)
-    requires knowing the concrete form of every token
   document the .messages file format
     likely pitfall: if Menhir says, "foo" is not a valid nonterminal symbol,
     then look for a blank line, higher up, between two sentences.
-    explain the meaning of the spurious reductions warning
+    explain the meaning of the spurious reductions warning (sometimes missing!)
     --compile-errors could warn about messages wider than 80 columns
     could also warn statically about out-of-range $i?
   document the workflow
-  collect performance data
-    correlate with star size and alphabet size, etc.
-    create separate graphs for 3 modes: --lalr, pager, --canonical
   remove lr.csv when done
   Could --interpret-error obey --trace?
-  Auto-comment: show the shape of the stack (invariant).
-  Idea: allow the user to make assertions about
-    the known shape of the stack,
-    the known lhs of all items in the state,
-    the possible continuations...?
-  Idea: investigate the use of placeholders (in the message)
-        that could be filled with dynamic information!
 
 * Clear up the Windows path confusion. Can we use "/" in Menhir's
   source code and in the Makefiles? Does OPAM work on Windows?

src/interpret.ml

-(* This module is in charge of handling the [--interpret] option,
-   if it is present. *)
-
 module I = Invariant (* artificial dependency; ensures that [Invariant] runs first *)
 
 (* --------------------------------------------------------------------------- *)
@@ -739,3 +736,24 @@ let () =
     exit 0
   )
 
+(* --------------------------------------------------------------------------- *)
+
+(* If [--echo-errors <filename>] is set, echo the error sentences found in file
+   [filename]. Do not echo the error messages or the comments. *)
+
+let () =
+  Settings.echo_errors |> Option.iter (fun filename ->
+
+    (* Read the file. *)
+    let runs : run or_comment list = read_messages filename in
+
+    (* Echo. *)
+    List.iter (or_comment_iter (fun run ->
+      let (sentences : located_sentence or_comment list), _, _ = run in
+      List.iter (or_comment_iter (fun (_, sentence) ->
+        print_string (print_sentence sentence)
+      )) sentences
+    )) runs
+
+  )
+

src/sentenceParserAux.ml

@@ -16,6 +16,12 @@ type 'a or_comment =
 | Thing of 'a
 | Comment of comment
 
+let or_comment_iter f = function
+  | Thing s ->
+      f s
+  | Comment _ ->
+      ()
+
 let or_comment_map f = function
   | Thing s ->
       Thing (f s)

src/settings.ml

@@ -191,6 +191,12 @@ let update_errors =
 let set_update_errors filename =
   update_errors := Some filename
 
+let echo_errors =
+  ref None
+
+let set_echo_errors filename =
+  echo_errors := Some filename
+
 let on_error_reduce_symbols =
   ref StringSet.empty
 
@@ -208,6 +214,7 @@ let options = Arg.align [
   "--coq-no-actions", Arg.Set coq_no_actions, " Ignore semantic actions in the Coq output";
   "--depend", Arg.Unit (fun () -> depend := OMPostprocess), " Invoke ocamldep and display dependencies";
   "--dump", Arg.Set dump, " Describe the automaton in <basename>.automaton";
+  "--echo-errors", Arg.String set_echo_errors, "<filename> Echo the sentences in a .messages file";
   "--error-recovery", Arg.Set recovery, " (no longer supported)";
   "--explain", Arg.Set explain, " Explain conflicts in <basename>.conflicts";
   "--external-tokens", Arg.String codeonly, "<module> Import token type definition from <module>";
@@ -465,6 +472,9 @@ let compare_errors =
 let update_errors =
   !update_errors
 
+let echo_errors =
+  !echo_errors
+
 let on_error_reduce nt =
   StringSet.mem nt !on_error_reduce_symbols
 

src/settings.mli

@@ -202,6 +202,12 @@ val compare_errors: (string * string) option
 
 val update_errors: string option
 
+(* This flag causes Menhir to read the error message descriptions stored in
+   [filename] and echo the error sentences (and nothing else; no messages,
+   no comments). *)
+
+val echo_errors: string option
+
 (* This function takes a non-terminal symbol and tells whether it appears
    in a command line switch of the form [--on-error-reduce]. This switch
    indicates that extra reductions are desired when an error is detected. *)