BridgeJS: Fix for-loop emission in stack codegen

Three `StackCodegen` helpers built their `for`-loops from separate
`CodeBlockItemSyntax` fragments ("for ... {", body, "}"). swift-syntax
603's formatter then renders such partial statements with the closing
brace glued to the previous line. Combine each for-loop into a single
multi-line `CodeBlockItemSyntax` so the formatter produces consistent
output across swift-syntax 600-603.

Also fix a latent bug in `StructCodegen.generateStructLowerCode` and
`EnumCodegen.generatePayloadPushingCode`: they concatenated lowering
statements via `CodeBlockItemListSyntax(statements).description` which
does not insert separators between items that lack leading trivia. The
thunk builder path was fine because `append` explicitly adds `.newline`
trivia, but any multi-statement lowering routed through a struct field
or enum payload was silently glued onto a single line. Iterate over the
statements and write each one individually through the printer.

Add regression coverage for the previously untested codepaths:

- `[String: MyProtocol]` as a function return, class property getter,
  and parameter (exercises `lowerProtocolDictionaryStatements`).
- A `@JS struct` field of type `[String: Int?]` (exercises
  `lowerDictionaryStatementsInline` via `generateStructLowerCode`).

Author: krodak

Plugins/BridgeJS/Sources/BridgeJSCore/ExportSwift.swift

@@ -827,15 +827,15 @@ struct StackCodegen {
         accessor: String,
         varPrefix: String
     ) -> [CodeBlockItemSyntax] {
-        var statements: [CodeBlockItemSyntax] = []
         let elemVar = "__bjs_elem_\(varPrefix)"
-        statements.append("for \(raw: elemVar) in \(raw: accessor) {")
-        statements.append(
-            "    _swift_js_push_i32((\(raw: elemVar) as! _BridgedSwiftProtocolExportable).bridgeJSLowerAsProtocolReturn())"
-        )
-        statements.append("}")
-        statements.append("_swift_js_push_i32(Int32(\(raw: accessor).count))")
-        return statements
+        return [
+            """
+            for \(raw: elemVar) in \(raw: accessor) {
+                _swift_js_push_i32((\(raw: elemVar) as! _BridgedSwiftProtocolExportable).bridgeJSLowerAsProtocolReturn())
+            }
+            """,
+            "_swift_js_push_i32(Int32(\(raw: accessor).count))",
+        ]
     }
 
     private func lowerDictionaryStatements(
@@ -866,49 +866,58 @@ struct StackCodegen {
         accessor: String,
         varPrefix: String
     ) -> [CodeBlockItemSyntax] {
-        var statements: [CodeBlockItemSyntax] = []
         let pairVarName = "__bjs_kv_\(varPrefix)"
-        statements.append("for \(raw: pairVarName) in \(raw: accessor) {")
-        statements.append("let __bjs_key_\(raw: varPrefix) = \(raw: pairVarName).key")
-        statements.append("let __bjs_value_\(raw: varPrefix) = \(raw: pairVarName).value")
-
-        let keyStatements = lowerStatements(
-            for: .string,
-            accessor: "__bjs_key_\(varPrefix)",
-            varPrefix: "\(varPrefix)_key"
+        let keyVarName = "__bjs_key_\(varPrefix)"
+        let valueVarName = "__bjs_value_\(varPrefix)"
+
+        // The dispatch in `lowerDictionaryStatements` routes only .nullable and .closure value
+        // types into this helper, both of which produce single-line lowering statements, so we can
+        // join their descriptions into the for-body as plain lines without worrying about nested
+        // multi-statement lowering.
+        var bodyLines: [String] = [
+            "let \(keyVarName) = \(pairVarName).key",
+            "let \(valueVarName) = \(pairVarName).value",
+        ]
+        bodyLines.append(
+            contentsOf: lowerStatements(
+                for: .string,
+                accessor: keyVarName,
+                varPrefix: "\(varPrefix)_key"
+            ).map { $0.description }
         )
-        for stmt in keyStatements {
-            statements.append(stmt)
-        }
-
-        let valueStatements = lowerStatements(
-            for: valueType,
-            accessor: "__bjs_value_\(varPrefix)",
-            varPrefix: "\(varPrefix)_value"
+        bodyLines.append(
+            contentsOf: lowerStatements(
+                for: valueType,
+                accessor: valueVarName,
+                varPrefix: "\(varPrefix)_value"
+            ).map { $0.description }
         )
-        for stmt in valueStatements {
-            statements.append(stmt)
-        }
+        let body = bodyLines.joined(separator: "\n    ")
 
-        statements.append("}")
-        statements.append("_swift_js_push_i32(Int32(\(raw: accessor).count))")
-        return statements
+        return [
+            """
+            for \(raw: pairVarName) in \(raw: accessor) {
+                \(raw: body)
+            }
+            """,
+            "_swift_js_push_i32(Int32(\(raw: accessor).count))",
+        ]
     }
 
     private func lowerProtocolDictionaryStatements(
         accessor: String,
         varPrefix: String
     ) -> [CodeBlockItemSyntax] {
-        var statements: [CodeBlockItemSyntax] = []
         let pairVar = "__bjs_kv_\(varPrefix)"
-        statements.append("for \(raw: pairVar) in \(raw: accessor) {")
-        statements.append("    \(raw: pairVar).key.bridgeJSStackPush()")
-        statements.append(
-            "    _swift_js_push_i32((\(raw: pairVar).value as! _BridgedSwiftProtocolExportable).bridgeJSLowerAsProtocolReturn())"
-        )
-        statements.append("}")
-        statements.append("_swift_js_push_i32(Int32(\(raw: accessor).count))")
-        return statements
+        return [
+            """
+            for \(raw: pairVar) in \(raw: accessor) {
+                \(raw: pairVar).key.bridgeJSStackPush()
+                _swift_js_push_i32((\(raw: pairVar).value as! _BridgedSwiftProtocolExportable).bridgeJSLowerAsProtocolReturn())
+            }
+            """,
+            "_swift_js_push_i32(Int32(\(raw: accessor).count))",
+        ]
     }
 }
 
@@ -1073,7 +1082,9 @@ struct EnumCodegen {
                 accessor: paramName,
                 varPrefix: paramName
             )
-            printer.write(multilineString: CodeBlockItemListSyntax(statements).description)
+            for statement in statements {
+                printer.write(multilineString: statement.description)
+            }
         }
     }
 
@@ -1207,7 +1218,9 @@ struct StructCodegen {
                 accessor: accessor,
                 varPrefix: property.name
             )
-            printer.write(multilineString: CodeBlockItemListSyntax(statements).description)
+            for statement in statements {
+                printer.write(multilineString: statement.description)
+            }
         }
 
         return printer.lines

Plugins/BridgeJS/Tests/BridgeJSToolTests/Inputs/MacroSwift/DictionaryTypes.swift

@@ -6,10 +6,16 @@
     }
 }
 
+@JS struct Counters {
+    var name: String
+    var counts: [String: Int?]
+}
+
 @JS func mirrorDictionary(_ values: [String: Int]) -> [String: Int]
 @JS func optionalDictionary(_ values: [String: String]?) -> [String: String]?
 @JS func nestedDictionary(_ values: [String: [Int]]) -> [String: [Int]]
 @JS func boxDictionary(_ boxes: [String: Box]) -> [String: Box]
 @JS func optionalBoxDictionary(_ boxes: [String: Box?]) -> [String: Box?]
+@JS func roundtripCounters(_ counters: Counters) -> Counters
 
 @JSFunction func importMirrorDictionary(_ values: [String: Double]) throws(JSException) -> [String: Double]

Plugins/BridgeJS/Tests/BridgeJSToolTests/Inputs/MacroSwift/Protocol.swift

@@ -102,8 +102,12 @@ import JavaScriptKit
     @JS
     var delegates: [MyViewControllerDelegate]
 
+    @JS
+    var delegatesByName: [String: MyViewControllerDelegate]
+
     @JS init(delegates: [MyViewControllerDelegate]) {
         self.delegates = delegates
+        self.delegatesByName = [:]
     }
 
     @JS func notifyAll() {
@@ -114,3 +118,7 @@ import JavaScriptKit
 }
 
 @JS func processDelegates(_ delegates: [MyViewControllerDelegate]) -> [MyViewControllerDelegate]
+
+@JS func processDelegatesByName(
+    _ delegates: [String: MyViewControllerDelegate]
+) -> [String: MyViewControllerDelegate]

Plugins/BridgeJS/Tests/BridgeJSToolTests/__Snapshots__/BridgeJSCodegenTests/DictionaryTypes.json

@@ -221,13 +221,78 @@
             }
           }
         }
+      },
+      {
+        "abiName" : "bjs_roundtripCounters",
+        "effects" : {
+          "isAsync" : false,
+          "isStatic" : false,
+          "isThrows" : false
+        },
+        "name" : "roundtripCounters",
+        "parameters" : [
+          {
+            "label" : "_",
+            "name" : "counters",
+            "type" : {
+              "swiftStruct" : {
+                "_0" : "Counters"
+              }
+            }
+          }
+        ],
+        "returnType" : {
+          "swiftStruct" : {
+            "_0" : "Counters"
+          }
+        }
       }
     ],
     "protocols" : [
 
     ],
     "structs" : [
+      {
+        "methods" : [
+
+        ],
+        "name" : "Counters",
+        "properties" : [
+          {
+            "isReadonly" : true,
+            "isStatic" : false,
+            "name" : "name",
+            "type" : {
+              "string" : {
 
+              }
+            }
+          },
+          {
+            "isReadonly" : true,
+            "isStatic" : false,
+            "name" : "counts",
+            "type" : {
+              "dictionary" : {
+                "_0" : {
+                  "nullable" : {
+                    "_0" : {
+                      "integer" : {
+                        "_0" : {
+                          "isSigned" : true,
+                          "width" : "word"
+                        }
+                      }
+                    },
+                    "_1" : "null"
+                  }
+                }
+              }
+            }
+          }
+        ],
+        "swiftCallName" : "Counters"
+      }
     ]
   },
   "imported" : {

Plugins/BridgeJS/Tests/BridgeJSToolTests/__Snapshots__/BridgeJSCodegenTests/DictionaryTypes.swift

@@ -1,3 +1,57 @@
+extension Counters: _BridgedSwiftStruct {
+    @_spi(BridgeJS) @_transparent public static func bridgeJSStackPop() -> Counters {
+        let counts = [String: Optional<Int>].bridgeJSStackPop()
+        let name = String.bridgeJSStackPop()
+        return Counters(name: name, counts: counts)
+    }
+
+    @_spi(BridgeJS) @_transparent public consuming func bridgeJSStackPush() {
+        self.name.bridgeJSStackPush()
+        for __bjs_kv_counts in self.counts {
+            let __bjs_key_counts = __bjs_kv_counts.key
+            let __bjs_value_counts = __bjs_kv_counts.value
+            __bjs_key_counts.bridgeJSStackPush()
+            __bjs_value_counts.bridgeJSStackPush()
+        }
+        _swift_js_push_i32(Int32(self.counts.count))
+    }
+
+    init(unsafelyCopying jsObject: JSObject) {
+        _bjs_struct_lower_Counters(jsObject.bridgeJSLowerParameter())
+        self = Self.bridgeJSStackPop()
+    }
+
+    func toJSObject() -> JSObject {
+        let __bjs_self = self
+        __bjs_self.bridgeJSStackPush()
+        return JSObject(id: UInt32(bitPattern: _bjs_struct_lift_Counters()))
+    }
+}
+
+#if arch(wasm32)
+@_extern(wasm, module: "bjs", name: "swift_js_struct_lower_Counters")
+fileprivate func _bjs_struct_lower_Counters_extern(_ objectId: Int32) -> Void
+#else
+fileprivate func _bjs_struct_lower_Counters_extern(_ objectId: Int32) -> Void {
+    fatalError("Only available on WebAssembly")
+}
+#endif
+@inline(never) fileprivate func _bjs_struct_lower_Counters(_ objectId: Int32) -> Void {
+    return _bjs_struct_lower_Counters_extern(objectId)
+}
+
+#if arch(wasm32)
+@_extern(wasm, module: "bjs", name: "swift_js_struct_lift_Counters")
+fileprivate func _bjs_struct_lift_Counters_extern() -> Int32
+#else
+fileprivate func _bjs_struct_lift_Counters_extern() -> Int32 {
+    fatalError("Only available on WebAssembly")
+}
+#endif
+@inline(never) fileprivate func _bjs_struct_lift_Counters() -> Int32 {
+    return _bjs_struct_lift_Counters_extern()
+}
+
 @_expose(wasm, "bjs_mirrorDictionary")
 @_cdecl("bjs_mirrorDictionary")
 public func _bjs_mirrorDictionary() -> Void {
@@ -53,6 +107,17 @@ public func _bjs_optionalBoxDictionary() -> Void {
     #endif
 }
 
+@_expose(wasm, "bjs_roundtripCounters")
+@_cdecl("bjs_roundtripCounters")
+public func _bjs_roundtripCounters() -> Void {
+    #if arch(wasm32)
+    let ret = roundtripCounters(_: Counters.bridgeJSLiftParameter())
+    return ret.bridgeJSLowerReturn()
+    #else
+    fatalError("Only available on WebAssembly")
+    #endif
+}
+
 @_expose(wasm, "bjs_Box_deinit")
 @_cdecl("bjs_Box_deinit")
 public func _bjs_Box_deinit(_ pointer: UnsafeMutableRawPointer) -> Void {

Plugins/BridgeJS/Tests/BridgeJSToolTests/__Snapshots__/BridgeJSCodegenTests/Protocol.json

@@ -317,6 +317,20 @@
                 }
               }
             }
+          },
+          {
+            "isReadonly" : false,
+            "isStatic" : false,
+            "name" : "delegatesByName",
+            "type" : {
+              "dictionary" : {
+                "_0" : {
+                  "swiftProtocol" : {
+                    "_0" : "MyViewControllerDelegate"
+                  }
+                }
+              }
+            }
           }
         ],
         "swiftCallName" : "DelegateManager"
@@ -502,6 +516,39 @@
             }
           }
         }
+      },
+      {
+        "abiName" : "bjs_processDelegatesByName",
+        "effects" : {
+          "isAsync" : false,
+          "isStatic" : false,
+          "isThrows" : false
+        },
+        "name" : "processDelegatesByName",
+        "parameters" : [
+          {
+            "label" : "_",
+            "name" : "delegates",
+            "type" : {
+              "dictionary" : {
+                "_0" : {
+                  "swiftProtocol" : {
+                    "_0" : "MyViewControllerDelegate"
+                  }
+                }
+              }
+            }
+          }
+        ],
+        "returnType" : {
+          "dictionary" : {
+            "_0" : {
+              "swiftProtocol" : {
+                "_0" : "MyViewControllerDelegate"
+              }
+            }
+          }
+        }
       }
     ],
     "protocols" : [