avm2: implement string.split for undefined (#5064)

* avm2: implement string.split for undefined

* chore: cargo fmt

* dev: avoid explicit ArrayStorage

CONTRIBUTING.md

@@ -143,7 +143,8 @@ To add a test here, create a .swf file that runs `trace()` statements. You can d
     * [`mtasc`](http://web.archive.org/web/20210324063628/http://tech.motion-twin.com/mtasc.html) (ActionScript 2 only)
         * if you create a file `test.as` with a `class Test` with a `static function main` with the code you want to run, you can compile it using `mtasc -main -header 200:150:30 test.as -swf test.swf`
     * [`mxmlc`](https://helpx.adobe.com/air/kb/archived-air-sdk-version.html) (ActionScript 3 only)
-        * if you create a file `test.as`, you can compile it using `mxmlc test.as`. `mxmlc` is located in the `bin` folder of the downloadable AIR SDK.
+        * if you create a file `test.as` with a `class Test`, you can compile it using `mxmlc Test.as`. `mxmlc` is located in the `bin` folder of the downloadable AIR SDK.
+        * you may want to use docker instead -- something like `docker run -it --rm -v ${PWD}:/src jeko/airbuild mxmlc ./Test.as` works well
 
 Run the .swf in Flash Player and create a file `output.txt` with the contents of the trace statements. Add the `output.txt`, `test.swf` and either the `test.as` or `test.fla` file to a directory under `core/tests/swfs/avm1` (or `avm2`) named after what your test tests, and add a line in `regression_tests.rs` to have Ruffle run it.
 

core/src/avm2/globals/string.rs

@@ -11,6 +11,7 @@ use crate::avm2::ArrayObject;
 use crate::avm2::Error;
 use crate::string_utils;
 use gc_arena::{GcCell, MutationContext};
+use std::iter;
 
 /// Implements `String`'s instance initializer.
 pub fn instance_init<'gc>(
@@ -126,12 +127,16 @@ fn split<'gc>(
     args: &[Value<'gc>],
 ) -> Result<Value<'gc>, Error> {
     if let Some(this) = this {
-        if matches!(args.get(0).unwrap_or(&Value::Undefined), Value::Undefined) {
+        let delimiter = args.get(0).unwrap_or(&Value::Undefined);
-            log::warn!("string.split(undefined) - not implemented");
+        if matches!(delimiter, Value::Undefined) {
+            let this = Value::from(this);
+            return Ok(
+                ArrayObject::from_storage(activation, iter::once(this).collect())
+                    .unwrap()
+                    .into(),
+            );
         }
-        if args
+        if delimiter
-            .get(0)
-            .unwrap_or(&Value::Undefined)
             .coerce_to_object(activation)?
             .as_regexp()
             .is_some()
@@ -139,10 +144,7 @@ fn split<'gc>(
             log::warn!("string.split(regex) - not implemented");
         }
         let this = Value::from(this).coerce_to_string(activation)?;
-        let delimiter = args
+        let delimiter = delimiter.coerce_to_string(activation)?;
-            .get(0)
-            .unwrap_or(&Value::Undefined)
-            .coerce_to_string(activation)?;
         let limit = match args.get(1).unwrap_or(&Value::Undefined) {
             Value::Undefined => usize::MAX,
             limit => limit.coerce_to_i32(activation)?.max(0) as usize,

tests/tests/swfs/avm2/string_split/output.txt

@@ -5,5 +5,6 @@
 a,b,c
 // text.split("")
 a,.,b,.,c
-// text.split() - unimplemented
+// text.split()
+a.b.c
 // text.split(regex) - unimplemented

tests/tests/swfs/avm2/string_split/test.as

@@ -16,7 +16,8 @@ trace(text.split("."));
 trace('// text.split("")');
 trace(text.split(""));
 
-trace('// text.split() - unimplemented');
+trace('// text.split()');
+trace(text.split());
 trace('// text.split(regex) - unimplemented');