Add test coverage for bool(JsProxy) and fix some cases (#2803)

Resolves #2802 and several other oddities in the behavior of bool.

docs/project/changelog.md

@@ -102,6 +102,11 @@ substitutions:
   `ERRNO_CODES` APIs.
   {pr}`2582`
 
+- {{ Fix }} The `bool` operator on a `JsProxy` now behaves more consistently: it
+  returns `False` if JavaScript would say that `!!x` is `false`, or if `x` is an
+  empty container. Otherwise it returns `True`.
+  {pr}`2803`
+
 ### REPL
 
 - {{ Enhancement }} Add a spinner while the REPL is loading

src/core/hiwire.c

@@ -724,11 +724,20 @@ EM_JS_BOOL(bool, hiwire_get_bool, (JsRef idobj), {
   if (!val) {
     return false;
   }
+  // We want to return false on container types with size 0.
   if (val.size === 0) {
-    // I think things with a size are all container types.
+    if(/HTML[A-Za-z]*Element/.test(Object.prototype.toString.call(val))){
+      // HTMLSelectElement and HTMLInputElement can have size 0 but we still
+      // want to return true.
+      return true;
+    }
+    // I think other things with a size are container types.
     return false;
   }
-  if (Array.isArray(val) && val.length === 0) {
+  if (val.length === 0 && JsArray_Check(idobj)) {
+    return false;
+  }
+  if (val.byteLength === 0) {
     return false;
   }
   return true;

src/tests/test_jsproxy.py

@@ -87,15 +87,66 @@ def test_jsproxy_document(selenium):
     from js import document
 
     el = document.createElement("div")
+    assert el.tagName == "DIV"
+    assert bool(el)
+    assert not document.body.children
     document.body.appendChild(el)
+    assert document.body.children
     assert document.body.children.length == 1
-    assert document.body.children[0].tagName == "DIV"
+    assert document.body.children[0] == el
     assert repr(document) == "[object HTMLDocument]"
-    el = document.createElement("div")
     assert len(dir(el)) >= 200
     assert "appendChild" in dir(el)
 
 
+@pytest.mark.parametrize(
+    "js,result",
+    [
+        ("{}", False),
+        ("{a:1}", True),
+        ("[]", False),
+        ("[1]", True),
+        ("new Map()", False),
+        ("new Map([[0, 0]])", True),
+        ("new Set()", False),
+        ("new Set([0])", True),
+        ("class T {}; T", True),
+        ("class T {}; new T()", True),
+        ("new Uint8Array(0)", False),
+        ("new Uint8Array(1)", True),
+        ("new ArrayBuffer(0)", False),
+        ("new ArrayBuffer(1)", True),
+    ],
+)
+@run_in_pyodide
+def test_jsproxy_bool(selenium, js, result):
+    from pyodide.code import run_js
+
+    assert bool(run_js(js)) == result
+
+
+@pytest.mark.xfail_browsers(node="No document in node")
+@pytest.mark.parametrize(
+    "js,result",
+    [
+        ("document.createElement('div')", True),
+        ("document.createElement('select')", True),
+        ("document.createElement('p')", True),
+        ("document.createElement('style')", True),
+        ("document.createElement('ul')", True),
+        ("document.createElement('ul').style", True),
+        ("document.querySelectorAll('x')", False),
+        ("document.querySelectorAll('body')", True),
+        ("document.all", False),
+    ],
+)
+@run_in_pyodide
+def test_jsproxy_bool_html(selenium, js, result):
+    from pyodide.code import run_js
+
+    assert bool(run_js(js)) == result
+
+
 @pytest.mark.xfail_browsers(node="No ImageData in node")
 @run_in_pyodide
 def test_jsproxy_imagedata(selenium):