From 4f7137ddd8fdff76428165deaee1d7efc52a7d47 Mon Sep 17 00:00:00 2001
From: Mark Lauter <mark@marklauter.com>
Date: Thu, 13 Jun 2024 00:52:30 -0400
Subject: [PATCH] added Catch extension for
 https://github.com/datalust/superpower/issues/87

---
 src/Superpower/ParserExtensions.cs | 58 ++++++++++++++++++++++++++++++
 1 file changed, 58 insertions(+)

diff --git a/src/Superpower/ParserExtensions.cs b/src/Superpower/ParserExtensions.cs
index 2f25f3e..2664500 100644
--- a/src/Superpower/ParserExtensions.cs
+++ b/src/Superpower/ParserExtensions.cs
@@ -115,5 +115,63 @@ public static bool IsMatch<T>(this TextParser<T> parser, TextSpan input)
             var result = parser(input);
             return result.HasValue && result.Remainder.IsAtEnd;
         }
+
+        /// <summary>
+        /// Attempts the parser and invokes the exceptionHandler if the parser throws <see cref="ParseException"/>.
+        /// </summary>
+        /// <typeparam name="TKind">The type of tokens consumed by the parser.</typeparam>
+        /// <typeparam name="T">The type of the result.</typeparam>
+        /// <param name="parser">The parser.</param>
+        /// <param name="exceptionHandler">A function that handles <see cref="ParseException"/> and returns a <see cref="TokenListParserResult{TKind, T}"/>.</param>
+        /// <returns>A parser that calls the first parser and handles <see cref="ParseException"/> by calling the exception handler.</returns>
+        /// <exception cref="ArgumentNullException">Thrown if either the parser or the exceptionHandler is null.</exception>
+        public static TokenListParser<TKind, T> Catch<TKind, T>(this TokenListParser<TKind, T> parser, Func<ParseException, TokenListParserResult<TKind, T>> exceptionHandler)
+        {
+            if (parser == null) throw new ArgumentNullException(nameof(parser));
+            if (exceptionHandler == null) throw new ArgumentNullException(nameof(exceptionHandler));
+
+            return input =>
+            {
+                try
+                {
+                    return parser(input);
+                }
+                catch (ParseException ex)
+                {
+                    return exceptionHandler(ex);
+                }
+            };
+        }
+
+        /// <summary>
+        /// Attempts the parser and invokes the exceptionHandler if the parser throws TException.
+        /// </summary>
+        /// <typeparam name="TException">The type of exception caught and handled by <see cref="Catch{TException, TKind, T}(TokenListParser{TKind, T}, Func{TException, TokenListParserResult{TKind, T}})"/></typeparam>
+        /// <typeparam name="TKind">The type of tokens consumed by the parser.</typeparam>
+        /// <typeparam name="T">The type of the result.</typeparam>
+        /// <param name="parser">The parser.</param>
+        /// <param name="exceptionHandler">A function that handles TException and returns a <see cref="TokenListParserResult{TKind, T}"/>.</param>
+        /// <returns>A parser that calls the first parser and handles TException by calling the exception handler.</returns>
+        /// <exception cref="ArgumentNullException">Thrown if either the parser or the exceptionHandler is null.</exception>
+        public static TokenListParser<TKind, T> Catch<TException, TKind, T>(
+            this TokenListParser<TKind, T> parser,
+            Func<TException, TokenListParserResult<TKind, T>> exceptionHandler)
+            where TException : Exception
+        {
+            if (parser == null) throw new ArgumentNullException(nameof(parser));
+            if (exceptionHandler == null) throw new ArgumentNullException(nameof(exceptionHandler));
+
+            return input =>
+            {
+                try
+                {
+                    return parser(input);
+                }
+                catch (TException ex)
+                {
+                    return exceptionHandler(ex);
+                }
+            };
+        }
     }
 }