lib-vt: disable logging in wasm release builds

src/lib_vt.zig

@@ -391,16 +391,15 @@ pub const std_options: std.Options = opts: {
     var options: std.Options = .{};
 
     if (builtin.target.cpu.arch.isWasm()) {
-        // Wasm builds we specifically want to optimize for space with small
-        // releases so we bump up to warn. Everything else acts pretty normal.
-        options.log_level = switch (builtin.mode) {
-            .Debug => .debug,
-            .ReleaseSmall => .warn,
-            else => .info,
-        };
-
-        // Wasm doesn't have access to stdio so we have a custom log function.
-        options.logFn = @import("os/wasm/log.zig").log;
+        // In non-debug modes, we want to ship effectively no logging
+        // warn and lower add ~200KB at the time of this comment.
+        if (builtin.mode == .Debug) {
+            options.log_level = .debug;
+            options.logFn = @import("os/wasm/log.zig").log;
+        } else {
+            options.log_level = .err;
+            options.logFn = @import("os/wasm/log.zig").noop;
+        }
     } else if (terminal.options.c_abi) {
         // For C ABI builds, use a custom log function that dispatches to an
         // embedder-provided callback (or silently discards when none is set).

src/os/wasm/log.zig

@@ -4,6 +4,22 @@ const wasm = @import("../wasm.zig");
 // Use the correct implementation
 pub const log = Freestanding.log;
 
+/// A log function that discards everything. Since the format string and
+/// scope are comptime parameters, using this compiles out all logging
+/// machinery: call sites, format strings, and the std.fmt code they
+/// reference (~220KB in a ReleaseFast wasm build).
+pub fn noop(
+    comptime level: std.log.Level,
+    comptime scope: @TypeOf(.EnumLiteral),
+    comptime format: []const u8,
+    args: anytype,
+) void {
+    _ = level;
+    _ = scope;
+    _ = format;
+    _ = args;
+}
+
 /// Freestanding implementation calls an extern "log" function.
 pub const Freestanding = struct {
     // The function std.log will call.