Fix locations reported by the parser (#609)

The start position of atoms wasn't saved by the parser.

CHANGES.md

@@ -41,6 +41,8 @@ next
 - Add a `best` mode which is native with fallback to byte-code when
   native compilation is not available (#23)
 
+- Fix locations reported in error messages (609)
+
 1.0+beta18 (25/02/2018)
 -----------------------
 

src/usexp/parser_automaton_internal.ml

@@ -176,9 +176,9 @@ type 'a epsilon_action = 'a state ->         stack -> stack
 let current_pos ?(delta=0) state : Lexing.position =
   let offset = state.offset + delta in
   { pos_fname = state.fname
-  ; pos_lnum   = state.line_number
-  ; pos_cnum   = offset
-  ; pos_bol    = state.bol_offset
+  ; pos_lnum  = state.line_number
+  ; pos_cnum  = offset
+  ; pos_bol   = state.bol_offset
   }
 
 let set_automaton_state state x = state.automaton_state <- x
@@ -211,16 +211,13 @@ let check_new_sexp_allowed : type a. a state -> unit = fun state ->
 let add_first_char state char stack =
   check_new_sexp_allowed state;
   Buffer.add_char state.atom_buffer char;
-  (* For non-quoted atoms, we save both positions at the end. We can always determine the
-     start position from the end position and the atom length for non-quoted atoms.
-
-     Doing it this way allows us to detect single characater atoms for which we need to
-     save the position twice. *)
+  state.token_start_pos <- current_pos state;
   stack
 
 let eps_add_first_char_hash state stack =
   check_new_sexp_allowed state;
   Buffer.add_char state.atom_buffer '#';
+  state.token_start_pos <- current_pos state ~delta:(-1);
   stack
 
 let start_quoted_string state _char stack =

test/blackbox-tests/test-cases/exclude-missing-module/run.t

@@ -1,3 +1,3 @@
   $ $JBUILDER build --display short --root . -j 1
-  File "jbuild", line 1, characters 0-50:
+  File "jbuild", line 3, characters 24-28:
   Warning: Module Fake is excluded but it doesn't exist.

test/blackbox-tests/test-cases/findlib/run.t

@@ -7,7 +7,7 @@
 Reproduction case for #484. The error should point to src/jbuild
 
   $ $JBUILDER build --root . -j1 --display quiet @install
-  File "src/jbuild", line 1, characters 0-66:
+  File "src/jbuild", line 4, characters 16-17:
   Error: Library "a" not found.
   Hint: try: jbuilder external-lib-deps --missing --root . @install
   [1]

test/blackbox-tests/test-cases/intf-only/run.t

@@ -38,8 +38,8 @@ Errors:
         ocamlc .foo.objs/foo.{cmi,cmo,cmt}
         ocamlc foo.cma
   $ $JBUILDER build --display short --root c -j1 foo.cma 2>&1 | grep -v Entering
-  File "jbuild", line 1, characters 0-58:
+  File "jbuild", line 3, characters 35-36:
   Error: Module X doesn't exist.
   $ $JBUILDER build --display short --root d -j1 foo.cma 2>&1 | grep -v Entering
-  File "jbuild", line 1, characters 0-58:
+  File "jbuild", line 3, characters 35-36:
   Error: Module X has an implementation, it cannot be listed here

test/blackbox-tests/test-cases/misc/run.t

@@ -1,5 +1,5 @@
   $ $JBUILDER runtest -j1 --display short --root .
-  File "jbuild", line 54, characters 10-209:
+  File "jbuild", line 65, characters 21-44:
   Warning: Directory dir-that-doesnt-exist doesn't exist.
           diff alias runtest
           diff alias runtest