From 788a716ac57b73b16a42db32d9f0a482cbbf385b Mon Sep 17 00:00:00 2001
From: Altagos <jakob@altagos.dev>
Date: Sat, 24 Jan 2026 16:20:55 +0000
Subject: [PATCH] pretty error types

---
 pretty.zig | 38 ++++++++++++++++++++++++++++++++------
 example/main.zig | 11 +++++++++++
 2 file(s) changed, 43 insertion(s)(+), 6 deletion(s)(-)

diff --git a/pretty.zig b/pretty.zig
--- a/pretty.zig
+++ b/pretty.zig
@@ -140,7 +140,7 @@
 };
 
 const InnerFmtOptions = struct {
-    dont_skip_type_name: bool = true,
+    skip_type_name: bool = !default_options.show_type_names,
 };
 
 fn innerFmt(
@@ -152,7 +152,7 @@
 ) error{WriteFailed}!void {
     const info = @typeInfo(T);
 
-    if (opts.dont_skip_type_name) try printType(T, ctx, run);
+    if (!opts.skip_type_name) try printType(T, ctx, run);
 
     return switch (info) {
         .bool => formatBool(ctx, run, value),
@@ -173,8 +173,8 @@
         .optional => |opt| formatOptional(opt.child, ctx, run, value),
         .@"struct" => |st| formatStruct(T, st, ctx, run, value),
 
-        // TODO: .error_union => |eu| {},
-        // TODO: .error_set => |es| {},
+        .error_set => formatErrorSet(ctx, run, value),
+        .error_union => formatErrorUnion(ctx, run, value),
 
         // TODO: .array => |arr| {},
         // TODO: .pointer => |ptr| {},
@@ -240,7 +240,7 @@
     value: ?T,
 ) !void {
     return if (value) |val|
-        innerFmt(T, ctx, run, val, .{ .dont_skip_type_name = false })
+        innerFmt(T, ctx, run, val, .{ .skip_type_name = true })
     else
         formatNull(ctx, run);
 }
@@ -265,7 +265,7 @@
         run.resetColor();
     }
 
-    comptime var index: comptime_int = 0;
+    comptime var index = 0;
     inline for (st.fields) |field| {
         indent(next_ctx, run);
         if (index != 0 and ctx.options.inline_structs) try run.write(", ");
@@ -284,6 +284,32 @@
         try run.write(" }");
         run.resetColor();
     }
+}
+
+inline fn formatErrorSet(
+    comptime ctx: Context,
+    run: *const Runtime,
+    value: anyerror,
+) !void {
+    run.setColor(ctx, .@"error");
+    try run.write("error.");
+    try run.write(@errorName(value));
+    run.resetColor();
+}
+
+inline fn formatErrorUnion(
+    comptime ctx: Context,
+    run: *Runtime,
+    value: anytype,
+) !void {
+    const val = value catch |err| return formatErrorSet(ctx, run, err);
+    return innerFmt(
+        @TypeOf(val),
+        ctx,
+        run,
+        val,
+        .{ .skip_type_name = true },
+    );
 }
 
 inline fn formatType(
diff --git a/example/main.zig b/example/main.zig
--- a/example/main.zig
+++ b/example/main.zig
@@ -33,6 +33,9 @@
     person: Person,
 };
 
+const ErrorSet = error{ OutOfMemory, WriteFailed };
+const Result = ErrorSet!Hello;
+
 pub fn main(init: std.process.Init) !void {
     _ = init;
 
@@ -96,4 +99,12 @@
         .{Pretty(Person, .{ .inline_structs = true }).init(person)},
     );
     print("Pretty nested struct - {f}\n", .{pretty(nested)});
+
+    const eu_error: Result = error.OutOfMemory;
+    const eu_ok: Result = .world;
+
+    print("\nError types\n", .{});
+    print("Error set - {f}\n", .{pretty(ErrorSet.OutOfMemory)});
+    print("Error union error - {f}\n", .{pretty(eu_error)});
+    print("Error union ok - {f}\n", .{pretty(eu_ok)});
 }

--
tangled.sh