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Merged
merged 5 commits into from
Oct 9, 2024
Merged

Add Fields to Java2Swift Tool #55

merged 5 commits into from
Oct 9, 2024

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jrosen081
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Closes #22

This PR adds support for exporting java fields into swift. The way I was able to test this was applying the following diff and then running the following commands (I can also add automated tests for this, but wasn't sure what the plan for automated tests for this tool are):

--- a/Samples/JavaKitSampleApp/src/main/java/com/example/swift/HelloSubclass.java
+++ b/Samples/JavaKitSampleApp/src/main/java/com/example/swift/HelloSubclass.java
@@ -15,7 +15,7 @@
 package com.example.swift;
 
 public class HelloSubclass extends HelloSwift {
-    private String greeting;
+    public String greeting;
 
     public HelloSubclass(String greeting) {
         this.greeting = greeting;
diff --git a/Samples/JavaKitSampleApp/src/main/java/com/example/swift/HelloSwift.java b/Samples/JavaKitSampleApp/src/main/java/com/example/swift/HelloSwift.java
index b4c87f7..3c89e2c 100644
--- a/Samples/JavaKitSampleApp/src/main/java/com/example/swift/HelloSwift.java
+++ b/Samples/JavaKitSampleApp/src/main/java/com/example/swift/HelloSwift.java
@@ -17,7 +17,8 @@ package com.example.swift;
 public class HelloSwift {
     private double value;
     private static double initialValue = 3.14159;
-    private String name = "Java";
+    public String name = "Java";
+    public static String staticName = "Static Java";
 
     static {
         System.loadLibrary("JavaKitExample");

And running the following commands from the base folder of the repo:

cd Samples/JavaKitSampleApp/src/main/java/com/example/swift/
javac -d ./build *.java
cd build/
jar -cf jar.jar *
swift run Java2Swift com.example.swift.HelloSubclass -o ./ --module-name Java2SwiftTest
cat HelloSubclass.swift

This prints out the following swift code (notice the 2 @JavaField annotations and not the static field, yet)

// Auto-generated by Java-to-Swift wrapper generator.
import JavaKit
import JavaRuntime

@JavaClass("com.example.swift.HelloSubclass")
public struct HelloSubclass {
  @JavaField
  public var greeting: String

  @JavaField
  public var name: String

  @JavaMethod
  public init(_ arg0: String, environment: JNIEnvironment)

  @JavaMethod
  public func greet(_ arg0: String)

  @JavaMethod
  public func sayHello(_ arg0: Int32, _ arg1: Int32) -> Int32

  @JavaMethod
  public func throwMessage(_ arg0: String) throws

  @JavaMethod
  public func throwMessageFromSwift(_ arg0: String) throws -> String

  @JavaMethod
  public func toString() -> String

  @JavaMethod
  public func hashCode() -> Int32

  @JavaMethod
  public func notify()

  @JavaMethod
  public func notifyAll()

  @JavaMethod
  public func wait(_ arg0: Int64) throws

  @JavaMethod
  public func wait(_ arg0: Int64, _ arg1: Int32) throws

  @JavaMethod
  public func wait() throws
}

@jrosen081 jrosen081 mentioned this pull request Oct 9, 2024
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DougGregor
DougGregor approved these changes Oct 9, 2024
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This looks great. The only real missing piece is how we test it... the testing of the Java2Swift path is not great right now, since we basically rely on regenerating its own sources (and not breaking) as "proof" that it didn't break. And unfortunately, none of the classes from the JDK that we build wrappers for include any public fields, so we don't see the effect of this change anywhere in the diff.

ktoso
ktoso approved these changes Oct 9, 2024
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LGTM, though we won't have CI test this change tbh. Building Java2Swift (make) fails right now afair, but it's a nice step.

@DougGregor
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DougGregor commented Oct 9, 2024 •
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I just had a wild/silly idea for unit testing this. What if we hook into

https://docs.oracle.com/javase/6/docs/api/javax/tools/JavaCompiler.html

in the unit tests so we can compile some Java code expressed as a string literal in Swift, then send that through Java2Swift and "diff" the expected output? If we wire it up correctly, it should make unit-testing changes to Java2Swift straightforward.

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ktoso commented Oct 9, 2024

Sure, why not I guess, anything that gets us some test coverage tbh :)

@ktoso ktoso merged commit 5ba87f6 into swiftlang:main Oct 9, 2024
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@jrosen081 jrosen081 mentioned this pull request Oct 10, 2024
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@ktoso ktoso ktoso approved these changes

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Generate @JavaField in Swift for the public fields of a Java class
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@jrosen081 @DougGregor @ktoso