BridgeJS: Support generic functions at the Swift and JavaScript boundary

Author: krodak

Plugins/BridgeJS/Sources/BridgeJSCore/ExportSwift.swift

@@ -143,6 +143,11 @@ public struct ImportTS {
         }
 
         func lowerParameter(param: Parameter) throws {
+            if case .generic = param.type {
+                stackLoweringStmts.insert("\(param.name).bridgeJSStackPush()", at: 0)
+                return
+            }
+
             let loweringInfo = try param.type.loweringParameterInfo(context: context)
 
             switch param.type {
@@ -241,6 +246,12 @@ public struct ImportTS {
             abiParameterForwardings.insert(contentsOf: ["resolveRef", "rejectRef"], at: 0)
         }
 
+        func appendTypeIDParameter(genericParameterName: String) {
+            let abiParamName = "\(genericParameterName.lowercased())TypeId"
+            abiParameterSignatures.append((abiParamName, .i32))
+            abiParameterForwardings.append("\(genericParameterName).bridgeJSTypeID")
+        }
+
         func call() throws {
             for stmt in stackLoweringStmts {
                 body.write(stmt.description)
@@ -298,6 +309,8 @@ public struct ImportTS {
             } else {
                 let liftExpr: String
                 switch returnType {
+                case .generic(let name):
+                    liftExpr = "\(name).bridgeJSStackPop()"
                 case .closure(let signature, _):
                     liftExpr = "_BJS_Closure_\(signature.mangleName).bridgeJSLift(ret)"
                 default:
@@ -363,7 +376,8 @@ public struct ImportTS {
             name: String,
             parameters: [Parameter],
             returnType: BridgeType,
-            effects: Effects
+            effects: Effects,
+            genericParameters: [String] = []
         ) -> DeclSyntax {
             let printer = CodeFragmentPrinter()
             let signature = SwiftSignatureBuilder.buildFunctionSignature(
@@ -372,7 +386,12 @@ public struct ImportTS {
                 effects: effects,
                 useWildcardLabels: true
             )
-            printer.write("func \(name.backtickIfNeeded())\(signature) {")
+            let genericClause =
+                genericParameters.isEmpty
+                ? ""
+                : "<" + genericParameters.map { "\($0): _BridgedSwiftGenericBridgeable" }.joined(separator: ", ")
+                    + ">"
+            printer.write("func \(name.backtickIfNeeded())\(genericClause)\(signature) {")
             printer.indent {
                 printer.write(lines: body.lines)
             }
@@ -432,6 +451,9 @@ public struct ImportTS {
         for param in function.parameters {
             try builder.lowerParameter(param: param)
         }
+        for genericParam in function.genericParameters {
+            builder.appendTypeIDParameter(genericParameterName: genericParam)
+        }
         try builder.call()
         try builder.liftReturnValue()
         topLevelDecls.append(builder.renderImportDecl())
@@ -440,7 +462,8 @@ public struct ImportTS {
                 name: Self.thunkName(function: function),
                 parameters: function.parameters,
                 returnType: function.returnType,
-                effects: function.effects
+                effects: function.effects,
+                genericParameters: function.genericParameters
             )
             .with(\.leadingTrivia, Self.renderDocumentation(documentation: function.documentation))
         ]
@@ -957,6 +980,8 @@ extension BridgeType {
             return LoweringParameterInfo(loweredParameters: params, useBorrowing: wrappedInfo.useBorrowing)
         case .array, .dictionary:
             return LoweringParameterInfo(loweredParameters: [])
+        case .generic:
+            return LoweringParameterInfo(loweredParameters: [])
         }
     }
 
@@ -1029,6 +1054,8 @@ extension BridgeType {
             return LiftingReturnInfo(valueToLift: wrappedInfo.valueToLift)
         case .array, .dictionary:
             return LiftingReturnInfo(valueToLift: nil)
+        case .generic:
+            return LiftingReturnInfo(valueToLift: nil)
         }
     }
 }