Allow to set a custom error handler in router configuration.

+ Add an option for a custom error handler and set a complete default one.
* Change handler context to allow its initialization without a matched route.
* Alphabetical order of HTTPError errors.

Author: Madeorsk

docs/getting_started.md

@@ -97,6 +97,15 @@ pub fn main() !void {
                 });
             }
         }.handler_fn,
+        .error_handler = struct {
+            fn handler_fn(ctx: *Context, _: anyerror) !void {
+                try ctx.respond(.{
+                    .status = .@"Internal Server Error",
+                    .mime = http.Mime.HTML,
+                    .body = "Oh no, Internal Server Error!",
+                });
+            }
+        }.handler_fn,
     });
 
     // This provides the entry function into the Tardy runtime. This will run

examples/basic/main.zig

@@ -78,6 +78,15 @@ pub fn main() !void {
                 });
             }
         }.handler_fn,
+        .error_handler = struct {
+            fn handler_fn(ctx: *Context, _: anyerror) !void {
+                try ctx.respond(.{
+                    .status = .@"Internal Server Error",
+                    .mime = http.Mime.HTML,
+                    .body = "Oh no, Internal Server Error!",
+                });
+            }
+        }.handler_fn,
     });
 
     // This provides the entry function into the Tardy runtime. This will run

src/http/context.zig

@@ -18,8 +18,6 @@ const _SSE = @import("sse.zig").SSE;
 const Runtime = @import("tardy").Runtime;
 const TaskFn = @import("tardy").TaskFn;
 
-const raw_respond = @import("server.zig").raw_respond;
-
 // Context is dependent on the server that gets created.
 pub fn Context(comptime Server: type, comptime AppState: type) type {
     return struct {
@@ -30,7 +28,7 @@ pub fn Context(comptime Server: type, comptime AppState: type) type {
         /// Custom user-data state.
         state: AppState,
         /// The matched route instance.
-        route: *const Route(Server, AppState),
+        route: ?*const Route(Server, AppState),
         /// The Request that triggered this handler.
         request: *const Request,
         /// The Response that will be returned.

src/http/lib.zig

@@ -9,10 +9,12 @@ pub const Headers = @import("../core/case_string_map.zig").CaseStringMap([]const
 pub const Server = @import("server.zig").Server;
 
 pub const HTTPError = error{
-    TooManyHeaders,
     ContentTooLarge,
-    MalformedRequest,
+    HTTPVersionNotSupported,
     InvalidMethod,
+    LengthRequired,
+    MalformedRequest,
+    MethodNotAllowed,
+    TooManyHeaders,
     URITooLong,
-    HTTPVersionNotSupported,
 };

src/http/router.zig

@@ -2,6 +2,8 @@ const std = @import("std");
 const log = std.log.scoped(.@"zzz/http/router");
 const assert = std.debug.assert;
 
+const HTTPError = @import("lib.zig").HTTPError;
+
 const _Route = @import("router/route.zig").Route;
 
 const Capture = @import("router/routing_trie.zig").Capture;
@@ -13,7 +15,13 @@ const _Context = @import("context.zig").Context;
 const _RoutingTrie = @import("router/routing_trie.zig").RoutingTrie;
 const QueryMap = @import("router/routing_trie.zig").QueryMap;
 
-/// Default not found handler: send a plain text response.
+/// Error handler type.
+pub fn ErrorHandlerFn(comptime Server: type, comptime AppState: type) type {
+    const Context = _Context(Server, AppState);
+    return *const fn (context: *Context, err: anyerror) anyerror!void;
+}
+
+/// Create a default not found handler: send a plain text response.
 pub fn default_not_found_handler(comptime Server: type, comptime AppState: type) _Route(Server, AppState).HandlerFn {
     const Context = _Context(Server, AppState);
 
@@ -28,6 +36,87 @@ pub fn default_not_found_handler(comptime Server: type, comptime AppState: type)
     }.not_found_handler;
 }
 
+/// Create a default error handler: send a plain text response with the error, if known, internal server error otherwise.
+pub fn default_error_handler(comptime Server: type, comptime AppState: type) ErrorHandlerFn(Server, AppState) {
+    const Context = _Context(Server, AppState);
+    return struct { fn f(ctx: *Context, err: anyerror) !void {
+        // Handle all default HTTP errors.
+        switch (err) {
+            HTTPError.ContentTooLarge => {
+                try ctx.respond(.{
+                    .status = .@"Content Too Large",
+                    .mime = Mime.TEXT,
+                    .body = "Request was too large.",
+                });
+            },
+            HTTPError.HTTPVersionNotSupported => {
+                try ctx.respond(.{
+                    .status = .@"HTTP Version Not Supported",
+                    .mime = Mime.HTML,
+                    .body = "HTTP version not supported.",
+                });
+            },
+            HTTPError.InvalidMethod => {
+                try ctx.respond(.{
+                    .status = .@"Not Implemented",
+                    .mime = Mime.TEXT,
+                    .body = "Not implemented.",
+                });
+            },
+            HTTPError.LengthRequired => {
+                try ctx.respond(.{
+                    .status = .@"Length Required",
+                    .mime = Mime.TEXT,
+                    .body = "Length required.",
+                });
+            },
+            HTTPError.MalformedRequest => {
+                try ctx.respond(.{
+                    .status = .@"Bad Request",
+                    .mime = Mime.TEXT,
+                    .body = "Malformed request.",
+                });
+            },
+            HTTPError.MethodNotAllowed => {
+                if (ctx.route) |route| {
+                    add_allow_header: {
+                        // We also need to add to Allow header.
+                        // This uses the connection's arena to allocate 64 bytes.
+                        const allowed = route.get_allowed(ctx.provision.arena.allocator()) catch break :add_allow_header;
+                        ctx.provision.response.headers.putAssumeCapacity("Allow", allowed);
+                    }
+                }
+                try ctx.respond(.{
+                    .status = .@"Method Not Allowed",
+                    .mime = Mime.TEXT,
+                    .body = "Method not allowed.",
+                });
+            },
+            HTTPError.TooManyHeaders => {
+                try ctx.respond(.{
+                    .status = .@"Request Header Fields Too Large",
+                    .mime = Mime.TEXT,
+                    .body = "Too many headers.",
+                });
+            },
+            HTTPError.URITooLong => {
+                try ctx.respond(.{
+                    .status = .@"URI Too Long",
+                    .mime = Mime.TEXT,
+                    .body = "URI too long.",
+                });
+            },
+            else => {
+                try ctx.respond(.{
+                    .status = .@"Internal Server Error",
+                    .mime = Mime.TEXT,
+                    .body = "Internal server error.",
+                });
+            },
+        }
+    } }.f;
+}
+
 /// Initialize a router with the given routes.
 pub fn Router(comptime Server: type, comptime AppState: type) type {
     return struct {
@@ -40,17 +129,20 @@ pub fn Router(comptime Server: type, comptime AppState: type) type {
         /// Router configuration structure.
         pub const Configuration = struct {
             not_found_handler: Route.HandlerFn = default_not_found_handler(Server, AppState),
+            error_handler: ErrorHandlerFn(Server, AppState) = default_error_handler(Server, AppState),
         };
 
         routes: RoutingTrie,
         not_found_route: Route,
+        error_handler: ErrorHandlerFn(Server, AppState),
         state: AppState,
 
         pub fn init(state: AppState, comptime _routes: []const Route, comptime configuration: Configuration) Self {
             const self = Self{
                 // Initialize the routing tree from the given routes.
                 .routes = comptime RoutingTrie.init(_routes),
                 .not_found_route = comptime Route.init("").all(configuration.not_found_handler),
+                .error_handler = configuration.error_handler,
                 .state = state,
             };