Create a top-level "third_party" directory

This directory now contains third_party software that is vendored into
the Servo source tree. The idea is that it would eventually hold
webrender and other crates from mozilla-central as well with a standard
patch management approach for each.

third_party/WebIDL/tests/test_union.py

@@ -0,0 +1,198 @@
+import WebIDL
+import itertools
+import string
+
+# We'd like to use itertools.chain but it's 2.6 or higher.
+
+
+def chain(*iterables):
+    # chain('ABC', 'DEF') --> A B C D E F
+    for it in iterables:
+        for element in it:
+            yield element
+
+
+# We'd like to use itertools.combinations but it's 2.6 or higher.
+def combinations(iterable, r):
+    # combinations('ABCD', 2) --> AB AC AD BC BD CD
+    # combinations(range(4), 3) --> 012 013 023 123
+    pool = tuple(iterable)
+    n = len(pool)
+    if r > n:
+        return
+    indices = list(range(r))
+    yield tuple(pool[i] for i in indices)
+    while True:
+        for i in reversed(range(r)):
+            if indices[i] != i + n - r:
+                break
+        else:
+            return
+        indices[i] += 1
+        for j in range(i + 1, r):
+            indices[j] = indices[j - 1] + 1
+        yield tuple(pool[i] for i in indices)
+
+
+# We'd like to use itertools.combinations_with_replacement but it's 2.7 or
+# higher.
+def combinations_with_replacement(iterable, r):
+    # combinations_with_replacement('ABC', 2) --> AA AB AC BB BC CC
+    pool = tuple(iterable)
+    n = len(pool)
+    if not n and r:
+        return
+    indices = [0] * r
+    yield tuple(pool[i] for i in indices)
+    while True:
+        for i in reversed(range(r)):
+            if indices[i] != n - 1:
+                break
+        else:
+            return
+        indices[i:] = [indices[i] + 1] * (r - i)
+        yield tuple(pool[i] for i in indices)
+
+
+def WebIDLTest(parser, harness):
+    types = [
+        "float",
+        "double",
+        "short",
+        "unsigned short",
+        "long",
+        "unsigned long",
+        "long long",
+        "unsigned long long",
+        "boolean",
+        "byte",
+        "octet",
+        "DOMString",
+        "ByteString",
+        "USVString",
+        # "sequence<float>",
+        "object",
+        "ArrayBuffer",
+        # "Date",
+        "TestInterface1",
+        "TestInterface2",
+    ]
+
+    testPre = """
+        interface TestInterface1 {
+        };
+        interface TestInterface2 {
+        };
+        """
+
+    interface = (
+        testPre
+        + """
+        interface PrepareForTest {
+        """
+    )
+    for (i, type) in enumerate(types):
+        interface += string.Template(
+            """
+          readonly attribute ${type} attr${i};
+        """
+        ).substitute(i=i, type=type)
+    interface += """
+        };
+        """
+
+    parser.parse(interface)
+    results = parser.finish()
+
+    iface = results[2]
+
+    parser = parser.reset()
+
+    def typesAreDistinguishable(t):
+        return all(u[0].isDistinguishableFrom(u[1]) for u in combinations(t, 2))
+
+    def typesAreNotDistinguishable(t):
+        return any(not u[0].isDistinguishableFrom(u[1]) for u in combinations(t, 2))
+
+    def unionTypeName(t):
+        if len(t) > 2:
+            t[0:2] = [unionTypeName(t[0:2])]
+        return "(" + " or ".join(t) + ")"
+
+    # typeCombinations is an iterable of tuples containing the name of the type
+    # as a string and the parsed IDL type.
+    def unionTypes(typeCombinations, predicate):
+        for c in typeCombinations:
+            if predicate(t[1] for t in c):
+                yield unionTypeName([t[0] for t in c])
+
+    # We limit invalid union types with a union member type to the subset of 3
+    # types with one invalid combination.
+    # typeCombinations is an iterable of tuples containing the name of the type
+    # as a string and the parsed IDL type.
+    def invalidUnionWithUnion(typeCombinations):
+        for c in typeCombinations:
+            if (
+                typesAreNotDistinguishable((c[0][1], c[1][1]))
+                and typesAreDistinguishable((c[1][1], c[2][1]))
+                and typesAreDistinguishable((c[0][1], c[2][1]))
+            ):
+                yield unionTypeName([t[0] for t in c])
+
+    # Create a list of tuples containing the name of the type as a string and
+    # the parsed IDL type.
+    types = zip(types, (a.type for a in iface.members))
+
+    validUnionTypes = chain(
+        unionTypes(combinations(types, 2), typesAreDistinguishable),
+        unionTypes(combinations(types, 3), typesAreDistinguishable),
+    )
+    invalidUnionTypes = chain(
+        unionTypes(combinations_with_replacement(types, 2), typesAreNotDistinguishable),
+        invalidUnionWithUnion(combinations(types, 3)),
+    )
+    interface = (
+        testPre
+        + """
+        interface TestUnion {
+        """
+    )
+    for (i, type) in enumerate(validUnionTypes):
+        interface += string.Template(
+            """
+          undefined method${i}(${type} arg);
+          ${type} returnMethod${i}();
+          attribute ${type} attr${i};
+          undefined optionalMethod${i}(${type}? arg);
+        """
+        ).substitute(i=i, type=type)
+    interface += """
+        };
+        """
+    parser.parse(interface)
+    results = parser.finish()
+
+    parser = parser.reset()
+
+    for invalid in invalidUnionTypes:
+        interface = (
+            testPre
+            + string.Template(
+                """
+            interface TestUnion {
+              undefined method(${type} arg);
+            };
+        """
+            ).substitute(type=invalid)
+        )
+
+        threw = False
+        try:
+            parser.parse(interface)
+            results = parser.finish()
+        except:
+            threw = True
+
+        harness.ok(threw, "Should have thrown.")
+
+        parser = parser.reset()