feat: expose extism_log_file on Plugin

src/Extism.Sdk/LibExtism.cs

@@ -289,7 +289,7 @@ internal struct ExtismPlugin { }
     unsafe internal static extern IntPtr extism_plugin_output_data(ExtismPlugin* plugin);
 
     /// <summary>
-    /// Set log file and level.
+    /// Set log file and level for file logger.
     /// </summary>
     /// <param name="filename"></param>
     /// <param name="logLevel"></param>
@@ -298,40 +298,28 @@ internal struct ExtismPlugin { }
     internal static extern bool extism_log_file(string filename, string logLevel);
 
     /// <summary>
-    /// Get Extism Runtime version.
+    /// Enable a custom log handler, this will buffer logs until `extism_log_drain` is called. 
+    /// this will buffer logs until `extism_log_drain` is called
     /// </summary>
+    /// <param name="logLevel"></param>
     /// <returns></returns>
     [DllImport("extism")]
-    internal static extern IntPtr extism_version();
+    internal static extern bool extism_log_custom(string logLevel);
+
+    internal delegate void LoggingSink(string line, ulong length);
 
     /// <summary>
-    /// Extism Log Levels
+    /// Calls the provided callback function for each buffered log line.
+    /// This is only needed when `extism_log_custom` is used.
     /// </summary>
-    internal static class LogLevels
-    {
-        /// <summary>
-        /// Designates very serious errors.
-        /// </summary>
-        internal const string Error = "Error";
-
-        /// <summary>
-        /// Designates hazardous situations.
-        /// </summary>
-        internal const string Warn = "Warn";
-
-        /// <summary>
-        /// Designates useful information.
-        /// </summary>
-        internal const string Info = "Info";
-
-        /// <summary>
-        /// Designates lower priority information.
-        /// </summary>
-        internal const string Debug = "Debug";
+    /// <param name="callback"></param>
+    [DllImport("extism")]
+    internal static extern void extism_log_drain(LoggingSink callback);
 
-        /// <summary>
-        /// Designates very low priority, often extremely verbose, information.
-        /// </summary>
-        internal const string Trace = "Trace";
-    }
+    /// <summary>
+    /// Get Extism Runtime version.
+    /// </summary>
+    /// <returns></returns>
+    [DllImport("extism")]
+    internal static extern IntPtr extism_version();
 }

src/Extism.Sdk/LogLevel.cs

@@ -8,12 +8,12 @@ public enum LogLevel
     /// <summary>
     /// Designates very serious errors.
     /// </summary>
-    Error,
+    Error = 1,
 
     /// <summary>
     /// Designates hazardous situations.
     /// </summary>
-    Warning,
+    Warn,
 
     /// <summary>
     /// Designates useful information.

src/Extism.Sdk/Plugin.cs

@@ -317,4 +317,44 @@ public static string ExtismVersion()
         var version = LibExtism.extism_version();
         return Marshal.PtrToStringAnsi(version);
     }
-}
+
+    /// <summary>
+    /// Set log file and level
+    /// </summary>
+    /// <param name="path">Log file path</param>
+    /// <param name="level">Minimum log level</param>
+    public static void ConfigureFileLogging(string path, LogLevel level)
+    {
+        var logLevel = Enum.GetName(typeof(LogLevel), level).ToLowerInvariant();
+        LibExtism.extism_log_file(path, logLevel);
+    }
+
+    /// <summary>
+    /// Enable a custom log handler, this will buffer logs until <see cref="DrainCustomLogs(LoggingSink)"/> is called.
+    /// </summary>
+    /// <param name="level"></param>
+    public static void ConfigureCustomLogging(LogLevel level)
+    {
+        var logLevel = Enum.GetName(typeof(LogLevel), level).ToLowerInvariant();
+        LibExtism.extism_log_custom(logLevel);
+    }
+
+    /// <summary>
+    /// Calls the provided callback function for each buffered log line.
+    /// This only needed when <see cref="ConfigureCustomLogging(LogLevel)"/> is used.
+    /// </summary>
+    /// <param name="callback"></param>
+    public static void DrainCustomLogs(LoggingSink callback)
+    {
+        LibExtism.extism_log_drain((line, length) =>
+        {
+            callback(line);
+        });
+    }
+}
+
+/// <summary>
+/// Custom logging callback.
+/// </summary>
+/// <param name="line"></param>
+public delegate void LoggingSink(string line);

test/Extism.Sdk/BasicTests.cs

@@ -1,5 +1,7 @@
 using Extism.Sdk.Native;
+
 using Shouldly;
+
 using System.Runtime.InteropServices;
 using System.Text;
 
@@ -178,6 +180,51 @@ public void HostFunctionsWithMemory()
         Encoding.UTF8.GetString(response).ShouldBe("HELLO FRODO!");
     }
 
+    [Fact]
+    public void FileLog()
+    {
+        var tempFile = Path.GetTempFileName();
+        Plugin.ConfigureFileLogging(tempFile, LogLevel.Warn);
+        using (var plugin = Helpers.LoadPlugin("log.wasm"))
+        {
+            plugin.Call("run_test", Array.Empty<byte>());
+        }
+
+        // HACK: tempFile gets locked by the Extism runtime 
+        var tempFile2 = Path.GetTempFileName();
+        File.Copy(tempFile, tempFile2, true);
+
+        var content = File.ReadAllText(tempFile2);
+        content.ShouldContain("warn");
+        content.ShouldContain("error");
+        content.ShouldNotContain("info");
+        content.ShouldNotContain("debug");
+        content.ShouldNotContain("trace");
+    }
+
+
+    // [Fact]
+    // Interferes with FileLog
+    internal void CustomLog()
+    {
+        var builder = new StringBuilder();
+
+        Plugin.ConfigureCustomLogging(LogLevel.Warn);
+        using (var plugin = Helpers.LoadPlugin("log.wasm"))
+        {
+            plugin.Call("run_test", Array.Empty<byte>());
+        }
+
+        Plugin.DrainCustomLogs(line => builder.AppendLine(line));
+
+        var content = builder.ToString();
+        content.ShouldContain("warn");
+        content.ShouldContain("error");
+        content.ShouldNotContain("info");
+        content.ShouldNotContain("debug");
+        content.ShouldNotContain("trace");
+    }
+
     public class CountVowelsResponse
     {
         public int Count { get; set; }

test/Extism.Sdk/Extism.Sdk.Tests.csproj

@@ -1,4 +1,4 @@
-<Project Sdk="Microsoft.NET.Sdk">
+<Project Sdk="Microsoft.NET.Sdk">
 
 	<PropertyGroup>
 		<TargetFramework>net7.0</TargetFramework>