Make WIT merging commutative (#2451)

* Make WIT merging commutative

Signed-off-by: Brian Hardock <brian.hardock@fermyon.com>

* Address PR feedback

Signed-off-by: Brian Hardock <brian.hardock@fermyon.com>

* Re-elaborate worlds after merge

Signed-off-by: Brian Hardock <brian.hardock@fermyon.com>

---------

Signed-off-by: Brian Hardock <brian.hardock@fermyon.com>

Author: fibonacci1729

crates/wit-component/tests/merge.rs

@@ -34,6 +34,9 @@ fn merging() -> Result<()> {
         from.assert_valid();
         into.assert_valid();
 
+        let from_clone = from.clone();
+        let into_clone = into.clone();
+
         match into.merge(from) {
             Ok(_) => {
                 assert!(
@@ -51,6 +54,13 @@ fn merging() -> Result<()> {
                     let output = printer.output.to_string();
                     assert_output(&expected, &output)?;
                 }
+
+                // Also assert merging in the reverse direction succeeds.
+                let mut reverse = from_clone;
+                reverse
+                    .merge(into_clone)
+                    .context("merge succeeded in one direction but failed in reverse")?;
+                reverse.assert_valid();
             }
             Err(e) => {
                 assert!(test_case.starts_with("bad-"), "failed to merge with {e:?}");

crates/wit-component/tests/merge/bad-interface1/error.txt

@@ -0,0 +1,5 @@
+package a:b;
+
+interface a {
+  f1: func();
+}

crates/wit-component/tests/merge/bad-interface2/error.txt

@@ -0,0 +1,5 @@
+package a:b;
+
+interface a {
+  f2: func();
+}

crates/wit-component/tests/merge/commutative-disjoint-funcs/from/a.wit

@@ -0,0 +1,8 @@
+package a:b;
+
+interface a {
+  f2: func();
+
+  f1: func();
+}
+

crates/wit-component/tests/merge/commutative-disjoint-funcs/into/a.wit

@@ -0,0 +1,23 @@
+package wasi:io@0.2.0;
+
+interface error {
+  resource error;
+}
+
+interface streams {
+  use error.{error};
+
+  resource output-stream {
+    check-write: func() -> result<u64, stream-error>;
+    write: func(contents: list<u8>) -> result<_, stream-error>;
+    blocking-write-and-flush: func(contents: list<u8>) -> result<_, stream-error>;
+    blocking-flush: func() -> result<_, stream-error>;
+  }
+
+  variant stream-error {
+    last-operation-failed(error),
+    closed,
+  }
+
+  resource input-stream;
+}

crates/wit-component/tests/merge/commutative-disjoint-funcs/merge/b.wit

@@ -0,0 +1,53 @@
+package wasi:io@0.2.0;
+
+interface error {
+  resource error {
+    to-debug-string: func() -> string;
+  }
+}
+
+interface poll {
+  resource pollable {
+    ready: func() -> bool;
+    block: func();
+  }
+
+  poll: func(in: list<borrow<pollable>>) -> list<u32>;
+}
+
+interface streams {
+  use error.{error};
+  use poll.{pollable};
+
+  variant stream-error {
+    last-operation-failed(error),
+    closed,
+  }
+
+  resource input-stream {
+    read: func(len: u64) -> result<list<u8>, stream-error>;
+    blocking-read: func(len: u64) -> result<list<u8>, stream-error>;
+    skip: func(len: u64) -> result<u64, stream-error>;
+    blocking-skip: func(len: u64) -> result<u64, stream-error>;
+    subscribe: func() -> pollable;
+  }
+
+  resource output-stream {
+    check-write: func() -> result<u64, stream-error>;
+    write: func(contents: list<u8>) -> result<_, stream-error>;
+    blocking-write-and-flush: func(contents: list<u8>) -> result<_, stream-error>;
+    flush: func() -> result<_, stream-error>;
+    blocking-flush: func() -> result<_, stream-error>;
+    subscribe: func() -> pollable;
+    write-zeroes: func(len: u64) -> result<_, stream-error>;
+    blocking-write-zeroes-and-flush: func(len: u64) -> result<_, stream-error>;
+    splice: func(src: borrow<input-stream>, len: u64) -> result<u64, stream-error>;
+    blocking-splice: func(src: borrow<input-stream>, len: u64) -> result<u64, stream-error>;
+  }
+}
+
+world imports {
+  import error;
+  import poll;
+  import streams;
+}

crates/wit-component/tests/merge/commutative/from/a.wit

@@ -0,0 +1,53 @@
+package wasi:io@0.2.0;
+
+interface error {
+  resource error {
+    to-debug-string: func() -> string;
+  }
+}
+
+interface poll {
+  resource pollable {
+    ready: func() -> bool;
+    block: func();
+  }
+
+  poll: func(in: list<borrow<pollable>>) -> list<u32>;
+}
+
+interface streams {
+  use error.{error};
+  use poll.{pollable};
+
+  variant stream-error {
+    last-operation-failed(error),
+    closed,
+  }
+
+  resource input-stream {
+    read: func(len: u64) -> result<list<u8>, stream-error>;
+    blocking-read: func(len: u64) -> result<list<u8>, stream-error>;
+    skip: func(len: u64) -> result<u64, stream-error>;
+    blocking-skip: func(len: u64) -> result<u64, stream-error>;
+    subscribe: func() -> pollable;
+  }
+
+  resource output-stream {
+    check-write: func() -> result<u64, stream-error>;
+    write: func(contents: list<u8>) -> result<_, stream-error>;
+    blocking-write-and-flush: func(contents: list<u8>) -> result<_, stream-error>;
+    flush: func() -> result<_, stream-error>;
+    blocking-flush: func() -> result<_, stream-error>;
+    subscribe: func() -> pollable;
+    write-zeroes: func(len: u64) -> result<_, stream-error>;
+    blocking-write-zeroes-and-flush: func(len: u64) -> result<_, stream-error>;
+    splice: func(src: borrow<input-stream>, len: u64) -> result<u64, stream-error>;
+    blocking-splice: func(src: borrow<input-stream>, len: u64) -> result<u64, stream-error>;
+  }
+}
+
+world imports {
+  import error;
+  import poll;
+  import streams;
+}