read/get-json: reject trailing junk in string input.

* parser.c (lisp_parse_impl): If parsing from string, check
for trailing junk and diagnose. JSON parsing doesn't use
lookahead because it doesn't have a.b syntax, so the
recent_tok gives the last token that actually went into the
syntax, and not a lookahead token. So in the case of JSON,
we call yylex to see if there is any trailing token.

* tests/010/json.tl: Extend get-json tests to more kinds of
objects, and then replicate with trailing whitespace and
trailing junk to provide coverage for these cases.

* tests/012/parse.t: Slew of new read tests and iread also.

* txr.1: Documented.

1 files changed, 16 insertions, 2 deletions

diff --git a/parser.c b/parser.c
index bc01c2bf..fd274ebb 100644
--- a/parser.c
+++ b/parser.c
@@ -636,11 +636,12 @@ static val lisp_parse_impl(val self, enum prime_parser prime,
 {
   uses_or2;
   val source = default_null_arg(source_in);
-  val input_stream = if3(stringp(source),
+  val str = stringp(source);
+  val input_stream = if3(str,
                          make_string_byte_input_stream(source),
                          or2(source, std_input));
   val name = or2(default_null_arg(name_in),
-                 if3(stringp(source),
+                 if3(str,
                      lit("string"),
                      stream_get_prop(input_stream, name_k)));
   val parser = ensure_parser(input_stream, name);
@@ -676,6 +677,19 @@ static val lisp_parse_impl(val self, enum prime_parser prime,
     break;
   }
 
+  if (str) {
+    int junk = 0;
+    if (prime == prime_json) {
+      yystype yyl;
+      junk = yylex(&yyl, pi->scanner);
+    } else {
+      junk = pi->recent_tok.yy_char;
+    }
+
+    if (junk)
+      yyerrorf(pi->scanner, lit("trailing material after expression"), nao);
+  }
+
   parsed = t;
 
   uw_unwind {