From 674bb08b20749d8aa866c6106c9c28bb729267df Mon Sep 17 00:00:00 2001
From: Evan Jones <evan.q.jones@gmail.com>
Date: Sun, 11 Jun 2023 22:40:01 -0400
Subject: [PATCH] handle & print parser errors

---
 examples/grammar-parser.cpp | 33 +++++++++++++++++++--------------
 examples/main/main.cpp      | 11 ++++++-----
 2 files changed, 25 insertions(+), 19 deletions(-)

diff --git a/examples/grammar-parser.cpp b/examples/grammar-parser.cpp
index 650c3cfc5..bdd48e796 100644
--- a/examples/grammar-parser.cpp
+++ b/examples/grammar-parser.cpp
@@ -47,7 +47,7 @@ namespace grammar_parser {
             pos++;
         }
         if (pos == src) {
-            throw std::string("expecting name at ") + src;
+            throw std::runtime_error(std::string("expecting name at ") + src);
         }
         return std::make_pair(pos, parse_space(pos));
     }
@@ -63,7 +63,7 @@ namespace grammar_parser {
                         return std::make_pair((first << 4) + second, src + 4);
                     }
                 }
-                throw std::string("expecting \\xNN at ") + src;
+                throw std::runtime_error(std::string("expecting \\xNN at ") + src);
             } else if (esc == '"' || esc == '[' || esc == ']') {
                 return std::make_pair(esc, src + 2);
             } else if (esc == 'r') {
@@ -73,11 +73,11 @@ namespace grammar_parser {
             } else if (esc == 't') {
                 return std::make_pair('\t', src + 2);
             }
-            throw std::string("unknown escape at ") + src;
+            throw std::runtime_error(std::string("unknown escape at ") + src);
         } else if (*src) {
             return std::make_pair(*src, src + 1);
         }
-        throw std::string("unexpected end of input");
+        throw std::runtime_error("unexpected end of input");
     }
 
     const char * parse_alternates(
@@ -151,12 +151,12 @@ namespace grammar_parser {
                 outbuf.push_back(1);
                 outbuf.push_back(sub_rule_id);
                 if (*pos != ')') {
-                    throw std::string("expecting ')' at ") + pos;
+                    throw std::runtime_error(std::string("expecting ')' at ") + pos);
                 }
                 pos = parse_space(pos + 1);
             } else if (*pos == '*' || *pos == '+' || *pos == '?') { // repetition operator
                 if (outbuf.size() - out_start - 1 == 0) {
-                    throw std::string("expecting preceeding item to */+/? at ") + pos;
+                    throw std::runtime_error(std::string("expecting preceeding item to */+/? at ") + pos);
                 }
                 std::vector<uint16_t> & out_grammar = state.out_grammar;
 
@@ -236,7 +236,7 @@ namespace grammar_parser {
         const std::string name(src, name_len);
 
         if (!(pos[0] == ':' && pos[1] == ':' && pos[2] == '=')) {
-            throw std::string("expecting ::= at ") + pos;
+            throw std::runtime_error(std::string("expecting ::= at ") + pos);
         }
         pos = parse_space(pos + 3);
 
@@ -247,19 +247,24 @@ namespace grammar_parser {
         } else if (*pos == '\n') {
             pos++;
         } else if (*pos) {
-            throw std::string("expecting newline or end at ") + pos;
+            throw std::runtime_error(std::string("expecting newline or end at ") + pos);
         }
         return parse_space(pos);
     }
 
     parse_state parse(const char * src) {
-        parse_state state;
-        const char * pos = parse_space(src);
-        while (*pos) {
-            pos = parse_rule(state, pos);
+        try {
+            parse_state state;
+            const char * pos = parse_space(src);
+            while (*pos) {
+                pos = parse_rule(state, pos);
+            }
+            state.out_grammar.push_back(0xffff);
+            return state;
+        } catch (const std::exception & err) {
+            fprintf(stderr, "%s: error parsing grammar: %s\n", __func__, err.what());
+            return parse_state();
         }
-        state.out_grammar.push_back(0xffff);
-        return state;
     }
 
     const uint16_t * print_rule(
diff --git a/examples/main/main.cpp b/examples/main/main.cpp
index 47b4728e9..8d9371e19 100644
--- a/examples/main/main.cpp
+++ b/examples/main/main.cpp
@@ -296,6 +296,10 @@ int main(int argc, char ** argv) {
     llama_grammar *             grammar = NULL;
     if (!params.grammar.empty()) {
         parsed_grammar = grammar_parser::parse(params.grammar.c_str());
+        // will be empty (default) if there are parse errors
+        if (parsed_grammar.out_grammar.empty()) {
+            return 1;
+        }
         fprintf(stderr, "%s: grammar:\n", __func__);
         grammar_parser::print_grammar(stderr, parsed_grammar);
         fprintf(stderr, "\n");
@@ -631,11 +635,8 @@ int main(int argc, char ** argv) {
             if (n_past > 0) {
                 if (is_interacting) {
                     // reset grammar state if we're restarting generation
-                    if (!params.grammar.empty()) {
-                        parsed_grammar = grammar_parser::parse(params.grammar.c_str());
-                        if (grammar != NULL) {
-                            llama_grammar_free(grammar);
-                        }
+                    if (grammar != NULL) {
+                        llama_grammar_free(grammar);
                         grammar = llama_grammar_init(
                             parsed_grammar.out_grammar.data(), parsed_grammar.symbol_ids.at("root"));
                     }