How to globally disable implicit #canImport(Foundation) availability?

taylorswift · March 29, 2025, 10:37pm

a “normal” WebAssembly build ought to end up producing something like this:

Size of original WebAssembly binary: 8.81 MB
Size after stripping debug symbols: 6.17 MB
Size after optimization: 3.91 MB

shockingly, after adding a dependency on WebAPIKit, it ballooned to

Size of original WebAssembly binary: 59.56 MB
Size after stripping debug symbols: 52.24 MB

as it turns out, WebAPIKit vends an overlay of Foundation, which is gated by #canImport(Foundation).

github.com/swiftwasm/WebAPIKit

Sources/ECMAScript/ArrayBuffer.swift

main


      
          #if canImport(Foundation)
              import Foundation
          
              public extension Data {
                  init(_ arrayBuffer: ArrayBuffer) {
                      self = JSTypedArray<UInt8>(arrayBuffer).withUnsafeBytes {
                          Data(buffer: $0)
                      }
                  }
          
                  init(_ sharedArrayBuffer: SharedArrayBuffer) {
                      self = JSTypedArray<UInt8>(sharedArrayBuffer).withUnsafeBytes {
                          Data(buffer: $0)
                      }
                  }
              }
          #endif

of course, just because one Can Import Foundation, does not mean one Should Import Foundation.

how can i disable #canImport(Foundation) availability at the package level, and apply this to dependencies such as the ECMAScript module from WebAPIKit?