From f05f004356e91f110f5297bdb61827a7c4436d2f Mon Sep 17 00:00:00 2001
From: Kaz Kylheku <kaz@kylheku.com>
Date: Fri, 28 May 2021 23:32:09 -0700
Subject: parser: provide parse-errors function.

* parser.c (parse_errors): New function.

* parser.h (parse_errors): Declared.

* txr.1: Documented.

* share/txr/stdlib/doc-syms.tl: Updated.
---
 parser.c                     | 14 ++++++++++++++
 parser.h                     |  1 +
 share/txr/stdlib/doc-syms.tl |  1 +
 txr.1                        | 42 ++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 58 insertions(+)

diff --git a/parser.c b/parser.c
index 1ab2e70b..3358d7bd 100644
--- a/parser.c
+++ b/parser.c
@@ -1683,6 +1683,19 @@ val parser_eof(val parser)
   return tnil(p->eof);
 }
 
+val parse_errors(val stream)
+{
+  val self = lit("parse-errors");
+  val errors = nil;
+  val parser = get_parser(stream);
+  if (parser) {
+    parser_t *p = coerce(parser_t *, cobj_handle(self, parser, parser_s));
+    if (p->errors)
+      errors = num(p->errors);
+  }
+  return errors;
+}
+
 static val circref(val n)
 {
   uw_throwf(error_s, lit("unresolved #~s# reference in object syntax"),
@@ -1876,6 +1889,7 @@ void parse_init(void)
   reg_fun(intern(lit("get-parser"), system_package), func_n1(get_parser));
   reg_fun(intern(lit("parser-errors"), system_package), func_n1(parser_errors));
   reg_fun(intern(lit("parser-eof"), system_package), func_n1(parser_eof));
+  reg_fun(intern(lit("parse-errors"), user_package), func_n1(parse_errors));
   reg_fun(intern(lit("repl"), system_package), func_n4(repl));
   reg_mac(json_s, func_n2(me_json));
 }
diff --git a/parser.h b/parser.h
index 5955447a..3c2e2292 100644
--- a/parser.h
+++ b/parser.h
@@ -143,4 +143,5 @@ val ensure_parser(val stream, val name);
 val parser_set_lineno(val self, val stream, val lineno);
 val parser_errors(val parser);
 val parser_eof(val parser);
+val parse_errors(val stream);
 void parse_init(void);
diff --git a/share/txr/stdlib/doc-syms.tl b/share/txr/stdlib/doc-syms.tl
index e92e8a4e..3f77d0d7 100644
--- a/share/txr/stdlib/doc-syms.tl
+++ b/share/txr/stdlib/doc-syms.tl
@@ -1330,6 +1330,7 @@
       ("parenb" "N-01B1B5DF")
       ("parmrk" "N-02391683")
       ("parodd" "N-01B1B5DF")
+      ("parse-errors" "N-00F843D4")
       ("partition" "N-0142889E")
       ("partition*" "N-03951D7A")
       ("partition-by" "N-000167DF")
diff --git a/txr.1 b/txr.1
index 12eae868..39afba58 100644
--- a/txr.1
+++ b/txr.1
@@ -56632,6 +56632,48 @@ it may be useful to set
 true in order to obtain better diagnostics. However, source location recording
 incurs a performance and storage penalty.
 
+.coNP Function @ parse-errors
+.synb
+.mets (parse-errors << stream )
+.syne
+.desc
+The
+.code parse-errors
+function retrieves information, from a
+.metn stream ,
+pertaining to the status of the most recent parsing operation performed
+on that stream: namely, a previous call to
+.codn read ,
+.code iread
+or
+.codn get-json .
+
+If the
+.meta stream
+object has not been used for parsing, or else the most recent
+parsing operation did not encounter errors, then
+.code parse-errors
+returns
+.codn nil .
+
+If the most recent parsing operation on
+.meta stream
+encountered errors, then
+.code parse-errors
+function returns a positive integer value indicating the error count.
+Otherwise it returns
+.codn nil .
+
+If a parse error operation encounters a syntax error before obtaining any token
+from the stream, then the error count is zero and
+.code parse-errors
+returns
+.codn nil .
+Consequently,
+.code parse-errors
+may be used after a failed parse operation to distinguish a true
+syntax error from an end-of-stream condition.
+
 .coNP Function @ record-adapter
 .synb
 .mets (record-adapter < regex >> [ stream <> [ include-match ]])
-- 
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