feat: publish bddkit-plugin.json with every release

.github/workflows/release.yml

@@ -170,3 +170,23 @@ jobs:
         env:
           GH_TOKEN: ${{ github.token }}
         run: gh release upload "$TAG" "$ASSET" "$ASSET.sha256" --clobber
+
+  abi-manifest:
+    name: bddkit-plugin.json
+    needs: release
+    if: ${{ always() && (inputs.rebuild_tag != '' || needs.release.outputs.created == 'true') }}
+    runs-on: ubuntu-latest
+    permissions:
+      contents: write
+    env:
+      TAG: ${{ inputs.rebuild_tag != '' && inputs.rebuild_tag || needs.release.outputs.tag }}
+    steps:
+      - uses: actions/checkout@v6
+        with:
+          ref: ${{ env.TAG }}
+
+      # Once per release, not from the per-target jobs, so they cannot race.
+      - name: Upload bddkit-plugin.json
+        env:
+          GH_TOKEN: ${{ github.token }}
+        run: gh release upload "$TAG" bddkit-plugin.json --clobber

bddkit-plugin.json

@@ -0,0 +1 @@
+{"abi": 2}

src/lib.rs

@@ -226,6 +226,17 @@ pub extern "C" fn bddkit_drop_instance(handle: u64) -> *mut c_char {
 
 #[cfg(test)]
 mod tests {
+    #[test]
+    fn bddkit_plugin_json_declares_the_abi_the_library_reports() {
+        let declared: serde_json::Value =
+            serde_json::from_str(include_str!("../bddkit-plugin.json")).expect("valid JSON");
+        assert_eq!(
+            declared["abi"],
+            crate::bddkit_abi_version(),
+            "bddkit-plugin.json must name the ABI bddkit_abi_version() returns"
+        );
+    }
+
     #[test]
     fn the_manifest_claims_the_browser_group_and_is_per_worker() {
         let v: serde_json::Value = serde_json::from_str(&crate::manifest_json()).expect("JSON");