From a09112404d40c1b3d5261a314b36e2f71b931f25 Mon Sep 17 00:00:00 2001
From: Calvin Rose <calsrose@gmail.com>
Date: Mon, 13 Apr 2020 23:18:27 -0500
Subject: [PATCH] Add better error message on unexpected eos.

Show innermost open delimiter
---
 src/core/parse.c    | 59 +++++++++++++++++++++++++++++++++------------
 src/core/pp.c       |  8 ++++++
 src/include/janet.h |  1 +
 3 files changed, 53 insertions(+), 15 deletions(-)

diff --git a/src/core/parse.c b/src/core/parse.c
index 6e479478..4e8bba04 100644
--- a/src/core/parse.c
+++ b/src/core/parse.c
@@ -26,6 +26,9 @@
 #include "util.h"
 #endif
 
+#define JANET_PARSER_DEAD 0x1
+#define JANET_PARSER_GENERATED_ERROR 0x2
+
 /* Check if a character is whitespace */
 static int is_whitespace(uint8_t c) {
     return c == ' '
@@ -637,11 +640,30 @@ void janet_parser_eof(JanetParser *parser) {
     size_t oldline = parser->line;
     janet_parser_consume(parser, '\n');
     if (parser->statecount > 1) {
-        parser->error = "unexpected end of source";
+        JanetParseState *s = parser->states + (parser->statecount - 1);
+        JanetBuffer *buffer = janet_buffer(40);
+        janet_buffer_push_cstring(buffer, "unexpected end of source: ");
+        if (s->flags & PFLAG_PARENS) {
+            janet_buffer_push_u8(buffer, '(');
+        } else if (s->flags & PFLAG_SQRBRACKETS) {
+            janet_buffer_push_u8(buffer, '[');
+        } else if (s->flags & PFLAG_CURLYBRACKETS) {
+            janet_buffer_push_u8(buffer, '{');
+        } else if (s->flags & PFLAG_STRING) {
+            janet_buffer_push_u8(buffer, '"');
+        } else if (s->flags & PFLAG_LONGSTRING) {
+            int32_t i;
+            for (i = 0; i < s->argn; i++) {
+                janet_buffer_push_u8(buffer, '`');
+            }
+        }
+        janet_formatbb(buffer, " opened at line %d, column %d", s->line, s->column);
+        parser->error = (const char *) janet_string(buffer->data, buffer->count);
+        parser->flag |= JANET_PARSER_GENERATED_ERROR;
     }
     parser->line = oldline;
     parser->column = oldcolumn;
-    parser->flag = 1;
+    parser->flag |= JANET_PARSER_DEAD;
 }
 
 enum JanetParserStatus janet_parser_status(JanetParser *parser) {
@@ -663,6 +685,7 @@ const char *janet_parser_error(JanetParser *parser) {
     if (status == JANET_PARSE_ERROR) {
         const char *e = parser->error;
         parser->error = NULL;
+        parser->flag &= ~JANET_PARSER_GENERATED_ERROR;
         janet_parser_flush(parser);
         return e;
     }
@@ -766,6 +789,9 @@ static int parsermark(void *p, size_t size) {
     for (i = 0; i < parser->argcount; i++) {
         janet_mark(parser->args[i]);
     }
+    if (parser->flag & JANET_PARSER_GENERATED_ERROR) {
+        janet_mark(janet_wrap_string(parser->error));
+    }
     return 0;
 }
 
@@ -900,7 +926,11 @@ static Janet cfun_parse_error(int32_t argc, Janet *argv) {
     janet_fixarity(argc, 1);
     JanetParser *p = janet_getabstract(argv, 0, &janet_parser_type);
     const char *err = janet_parser_error(p);
-    if (err) return janet_cstringv(err);
+    if (err) {
+        return (p->flag & JANET_PARSER_GENERATED_ERROR)
+               ? janet_wrap_string(err)
+               : janet_cstringv(err);
+    }
     return janet_wrap_nil();
 }
 
@@ -999,31 +1029,30 @@ struct ParserStateGetter {
 };
 
 static Janet parser_state_delimiters(const JanetParser *_p) {
-    JanetParser *clone = janet_abstract(&janet_parser_type, sizeof(JanetParser));
-    janet_parser_clone(_p, clone);
+    JanetParser *p = (JanetParser *)_p;
     size_t i;
     const uint8_t *str;
     size_t oldcount;
-    oldcount = clone->bufcount;
-    for (i = 0; i < clone->statecount; i++) {
-        JanetParseState *s = clone->states + i;
+    oldcount = p->bufcount;
+    for (i = 0; i < p->statecount; i++) {
+        JanetParseState *s = p->states + i;
         if (s->flags & PFLAG_PARENS) {
-            push_buf(clone, '(');
+            push_buf(p, '(');
         } else if (s->flags & PFLAG_SQRBRACKETS) {
-            push_buf(clone, '[');
+            push_buf(p, '[');
         } else if (s->flags & PFLAG_CURLYBRACKETS) {
-            push_buf(clone, '{');
+            push_buf(p, '{');
         } else if (s->flags & PFLAG_STRING) {
-            push_buf(clone, '"');
+            push_buf(p, '"');
         } else if (s->flags & PFLAG_LONGSTRING) {
             int32_t i;
             for (i = 0; i < s->argn; i++) {
-                push_buf(clone, '`');
+                push_buf(p, '`');
             }
         }
     }
-    str = janet_string(clone->buf + oldcount, (int32_t)(clone->bufcount - oldcount));
-    clone->bufcount = oldcount;
+    str = janet_string(p->buf + oldcount, (int32_t)(p->bufcount - oldcount));
+    p->bufcount = oldcount;
     return janet_wrap_string(str);
 }
 
diff --git a/src/core/pp.c b/src/core/pp.c
index b0c914fb..828e4c11 100644
--- a/src/core/pp.c
+++ b/src/core/pp.c
@@ -863,6 +863,14 @@ const uint8_t *janet_formatc(const char *format, ...) {
     return ret;
 }
 
+JanetBuffer *janet_formatbb(JanetBuffer *buffer, const char *format, ...) {
+    va_list args;
+    va_start(args, format);
+    janet_formatb(buffer, format, args);
+    va_end(args);
+    return buffer;
+}
+
 /* Shared implementation between string/format and
  * buffer/format */
 void janet_buffer_format(
diff --git a/src/include/janet.h b/src/include/janet.h
index 00975136..66cd1813 100644
--- a/src/include/janet.h
+++ b/src/include/janet.h
@@ -1239,6 +1239,7 @@ JANET_API void janet_description_b(JanetBuffer *buffer, Janet x);
 #define janet_stringv(str, len) janet_wrap_string(janet_string((str), (len)))
 JANET_API JanetString janet_formatc(const char *format, ...);
 JANET_API void janet_formatb(JanetBuffer *bufp, const char *format, va_list args);
+JANET_API JanetBuffer *janet_formatbb(JanetBuffer *bufp, const char *format, ...);
 
 /* Symbol functions */
 JANET_API JanetSymbol janet_symbol(const uint8_t *str, int32_t len);