Wave 3 (0.6.0): zero-OpenCombine builds on Apple platforms

.github/workflows/canary-upstreams.yml

@@ -195,10 +195,16 @@ jobs:
             --repo "${REPO}"
 
   # ---------------------------------------------------------------------------
-  # opencombine-latest: build against the latest OpenCombine release (host only).
+  # opencombine-latest: build against the latest OpenCombine release.
   #
   # Detects Scheduler/Publisher/Sendable API changes in OpenCombine that would
   # break the library before users see them.
+  #
+  # Since #15 the OpenCombine dependency is platform-conditional: a macOS host
+  # build links native Combine and compiles ZERO OpenCombine code, so the host
+  # steps below only validate dependency resolution against the latest tag.
+  # The wasm build steps (mirroring the jskit-latest job) are what actually
+  # compile the library against the patched OpenCombine.
   # ---------------------------------------------------------------------------
   opencombine-latest:
     name: Canary — Latest OpenCombine (#12)
@@ -251,7 +257,9 @@ jobs:
           rm -f Package.resolved
           swift package resolve
 
-      - name: Build host — latest OpenCombine
+      # Host build/test compile against native Combine since #15 (resolution
+      # smoke check only — no OpenCombine source is built on macOS).
+      - name: Build host — latest OpenCombine (resolution check)
         id: build-host
         run: swift build --target OpenCombineJS
 
@@ -261,6 +269,32 @@ jobs:
         id: test-host
         run: swift test || true
 
+      # Wasm build: the lane that actually compiles OpenCombine (see job header).
+      # Same SDK install/skip strategy as the jskit-latest job above.
+      - name: Install Swift wasm SDK (official, version-matched)
+        run: |
+          SWIFT_SEMVER=$(swift --version 2>/dev/null | grep -oE 'Swift version [0-9]+\.[0-9]+(\.[0-9]+)?' | grep -oE '[0-9]+\.[0-9]+(\.[0-9]+)?' | head -1)
+          SWIFT_TAG="swift-${SWIFT_SEMVER}-RELEASE"
+          # Note: .artifactbundle.tar.gz — there is no .zip variant on download.swift.org.
+          SDK_URL="https://download.swift.org/swift-${SWIFT_SEMVER}-release/wasm-sdk/${SWIFT_TAG}/${SWIFT_TAG}_wasm.artifactbundle.tar.gz"
+          echo "Downloading wasm Swift SDK from ${SDK_URL}"
+          if curl -fsSL "${SDK_URL}" -o /tmp/swift-wasm-sdk.tar.gz; then
+            swift sdk install /tmp/swift-wasm-sdk.tar.gz || true
+          else
+            echo "WARN: no official wasm SDK published for ${SWIFT_TAG}; skipping wasm canary build."
+          fi
+          swift sdk list || true
+
+      - name: Build wasm — latest OpenCombine
+        id: build-wasm
+        run: |
+          SDK_ID=$(swift sdk list 2>/dev/null | grep -i wasm | head -1 | awk '{print $1}' || echo "")
+          if [ -z "$SDK_ID" ]; then
+            echo "WARN: No wasm SDK found; skipping wasm build in this canary run."
+            exit 0
+          fi
+          swift build --swift-sdk "${SDK_ID}" --target OpenCombineJS -c debug
+
       - name: File canary-failure issue (if not already open)
         if: failure()
         env:

CHANGELOG.md

@@ -1,3 +1,19 @@
+# Unreleased (0.6.0)
+
+**Build/packaging change — no public API is removed or deprecated:**
+
+- The OpenCombine product dependency is now **platform-conditional**
+  (`.when(platforms: [.wasi, .linux, .android, .windows, .openbsd])`): on Apple platforms —
+  where the sources already build against native Combine via `#if canImport(Combine)` (#11) —
+  OpenCombine is no longer compiled or linked at all, giving Apple consumers a
+  zero-OpenCombine build. All non-Apple platforms keep OpenCombine as a full build-and-link
+  dependency, so WASI/Linux consumers are unaffected. The package-level
+  `.package(url: …/OpenCombine.git …)` declaration remains, so SwiftPM still *fetches*
+  OpenCombine (and its transitive swift-syntax) at resolution time on every platform; only
+  the build/linkage footprint drops. The OpenCombine upstream canary now exercises the wasm
+  lane, since a host build no longer compiles OpenCombine
+  ([#15](https://github.com/IGRSoft/OpenCombineJS/issues/15))
+
 # 0.5.0 (2026-06-11)
 
 **Additions (strictly non-breaking — the public API is additive only):**

CONTRIBUTING.md

@@ -37,9 +37,18 @@ Notes:
 ## Dependency version policy
 
 - Minimum **JavaScriptKit 0.54.1** (ships `JSPromise.value`, required by the async bridge, #13).
+- **OpenCombine is platform-conditional** (#15): the product dependency carries
+  `condition: .when(platforms: [.wasi, .linux, .android, .windows, .openbsd])` — every
+  non-Apple platform the 6.3 `PackageDescription` exposes. On Apple platforms the sources use
+  native Combine (`#if canImport(Combine)`, #11) and OpenCombine is neither compiled nor
+  linked; it is still fetched at resolution time because the package-level declaration stays.
+  When editing the platform list, keep it in sync with "platforms where `canImport(Combine)`
+  is false" — dropping one silently breaks that platform's build. Full removal of the
+  declaration is deferred until the Publisher surface is retired.
 - Weekly canaries ([canary-upstreams.yml](.github/workflows/canary-upstreams.yml)) build against
   the latest JavaScriptKit release and OpenCombine main. They are allowed to fail and auto-file
-  `canary-failure` issues instead of breaking CI.
+  `canary-failure` issues instead of breaking CI. Note the OpenCombine canary must build the
+  **wasm lane** — a macOS host build no longer compiles OpenCombine at all.
 - The moment JavaScriptKit ships a native `TopLevelDecoder` conformance, our retroactive one
   becomes a duplicate-conformance build error: delete `Sources/OpenCombineJS/JSValueDecoder.swift`
   and tag a minor release (#9). The JSKit canary exists to catch this early.

Package.swift

@@ -1,6 +1,16 @@
 // swift-tools-version:6.3
 import PackageDescription
 
+/// Platforms WITHOUT native Combine (`#if canImport(Combine)` is false there, so the
+/// sources fall back to `import OpenCombine` — see JSPromise.swift, #11/#15).
+/// Must list EVERY non-Apple platform PackageDescription 6.3 exposes, not just .wasi:
+/// dropping one (e.g. .linux) would silently unlink OpenCombine for its consumers and
+/// break their builds.  (.freebsd exists in the 6.3 swiftinterface but is gated
+/// @available(_PackageDescription 999.0) and therefore not usable yet.)
+/// On Apple platforms the condition keeps OpenCombine out of the build graph entirely:
+/// it is still FETCHED at dependency-resolution time, but never compiled or linked.
+let openCombinePlatforms: [Platform] = [.wasi, .linux, .android, .windows, .openbsd]
+
 let package = Package(
   name: "OpenCombineJS",
   platforms: [
@@ -24,20 +34,34 @@ let package = Package(
       name: "OpenCombineJSExample",
       dependencies: [
         "OpenCombineJS",
+        .product(
+          name: "OpenCombine",
+          package: "OpenCombine",
+          condition: .when(platforms: openCombinePlatforms)
+        ),
       ]
     ),
     .target(
       name: "OpenCombineJS",
       dependencies: [
-        "JavaScriptKit", "OpenCombine",
+        "JavaScriptKit",
+        .product(
+          name: "OpenCombine",
+          package: "OpenCombine",
+          condition: .when(platforms: openCombinePlatforms)
+        ),
       ]
     ),
     .testTarget(
       name: "OpenCombineJSTests",
       dependencies: [
         "OpenCombineJS",
         "JavaScriptKit",
-        "OpenCombine",
+        .product(
+          name: "OpenCombine",
+          package: "OpenCombine",
+          condition: .when(platforms: openCombinePlatforms)
+        ),
         // Installs the JavaScriptEventLoop global executor at startup so async tests can be
         // resumed by JS timers/promises. Only meaningful (and only linked) on WASI.
         .product(

README.md

@@ -17,6 +17,12 @@ APIs. Currently it provides:
 - A `publisher` property on [`JSPromise`](https://swiftwasm.github.io/JavaScriptKit/JSPromise/),
   which converts your [JavaScript `Promise`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise) instances to Combine publishers.
 
+On Apple platforms the library builds against the **native Combine framework and links no
+OpenCombine at all** — the OpenCombine dependency is declared platform-conditionally, so Apple
+consumers get a zero-OpenCombine build (it is still fetched at dependency-resolution time). On
+WASI, Linux, and other platforms without Combine it builds against
+[OpenCombine](https://github.com/OpenCombine/OpenCombine).
+
 ## Example
 
 Here's an example of a timer that fetches a UUID from a remote server every second, parses it

Sources/OpenCombineJS/Documentation.docc/OpenCombineJS.md

@@ -28,6 +28,12 @@ Apple platforms it builds against the **native Combine framework**, so `JSPromis
 symbol-for-symbol — only the module identity differs, so the same consumer code compiles on
 both backends.
 
+Since 0.6.0 the OpenCombine package dependency is also **platform-conditional**: on Apple
+platforms OpenCombine is neither compiled nor linked — Apple consumers get a
+zero-OpenCombine build (the package is still fetched when SwiftPM resolves the dependency
+graph). On WASI, Linux, and the other non-Apple platforms OpenCombine remains a full
+build-and-link dependency, exactly as before.
+
 ### Async/await usage
 
 `await`-based APIs require the `JavaScriptEventLoop` global executor on WASI