Include snippet of SQL which led to parsing error

Author: lustefaniak

src/parser.rs

@@ -316,8 +316,8 @@ impl<'a> Parser<'a> {
     pub fn try_with_sql(self, sql: &str) -> Result<Self, ParserError> {
         debug!("Parsing sql '{}'...", sql);
         let mut tokenizer = Tokenizer::new(self.dialect, sql);
-        let tokens = tokenizer.tokenize()?;
-        Ok(self.with_tokens(tokens))
+        let tokens = tokenizer.tokenize_with_location()?;
+        Ok(self.with_tokens_with_locations(tokens))
     }
 
     /// Parse potentially multiple statements
@@ -2160,7 +2160,24 @@ impl<'a> Parser<'a> {
 
     /// Report unexpected token
     pub fn expected<T>(&self, expected: &str, found: TokenWithLocation) -> Result<T, ParserError> {
-        parser_err!(format!("Expected {expected}, found: {found}"))
+        let start_off = self.index.saturating_sub(10);
+        let end_off = self.index.min(self.tokens.len());
+        let near_tokens = &self.tokens[start_off..end_off];
+        struct TokensDisplay<'a>(&'a [TokenWithLocation]);
+        impl<'a> fmt::Display for TokensDisplay<'a> {
+            fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+                for token in self.0 {
+                    write!(f, "{}", token)?;
+                }
+                Ok(())
+            }
+        }
+        parser_err!(format!(
+            "Expected {}, found: {}\nNear `{}`",
+            expected,
+            found,
+            TokensDisplay(near_tokens),
+        ))
     }
 
     /// Look for an expected keyword and consume it if it exists
@@ -7756,7 +7773,7 @@ mod tests {
         assert_eq!(
             ast,
             Err(ParserError::ParserError(
-                "Expected [NOT] NULL or TRUE|FALSE or [NOT] DISTINCT FROM after IS, found: a"
+                "Expected [NOT] NULL or TRUE|FALSE or [NOT] DISTINCT FROM after IS, found: a\nNear `SELECT this is`"
                     .to_string()
             ))
         );

tests/sqlparser_bigquery.rs

@@ -347,7 +347,7 @@ fn test_select_wildcard_with_except() {
             .parse_sql_statements("SELECT * EXCEPT () FROM employee_table")
             .unwrap_err()
             .to_string(),
-        "sql parser error: Expected identifier, found: )"
+        "sql parser error: Expected identifier, found: )\nNear `SELECT * EXCEPT ()`"
     );
 }