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, 17 insertions, 1 deletions

diff --git a/txr.1 b/txr.1
index 0e38dff4..ac6edd06 100644
--- a/txr.1
+++ b/txr.1
@@ -57319,7 +57319,23 @@ string, or a stream.  If it is omitted, then
 .code *stdin*
 is used as the stream.
 
-The source must provide the text representation of one complete \*(TL object.
+The
+.meta source
+must provide the text representation of one complete \*(TL object.
+If
+.meta source
+and the function being applied is
+.codn read ,
+then if the object is followed by any non-whitespace material, the
+situation is treated as a syntax error, even if that material is
+a syntactically valid additional object.
+The
+.code iread
+function ignores this situation. Other differences between
+.code read
+and
+.code iread
+are given below.
 
 Multiple calls to read on the same stream will extract successive objects
 from the stream. To parse successive objects from a string, it is necessary