Bind the C API for components (#308)

* Fix defining fields of forward-declared structures

This fixes a typo in the bindings generation script which set the
`_fields` field rather than `_fields_`

* Bind the C API for components

* Update to latest dev branch of wasmtime

* CI fixes

* Python 3.9 compat

Author: alexcrichton

ci/cbindgen.py

@@ -189,7 +189,10 @@ def type_name(ty, ptr=False, typing=False):
             return "POINTER({})".format(type_name(ty, False, typing))
 
     if isinstance(ty, c_ast.IdentifierType):
+        if ty.names == ['unsigned', 'char']:
+            return "int" if typing else "c_ubyte"
         assert(len(ty.names) == 1)
+
         if ty.names[0] == "void":
             return "None"
         elif ty.names[0] == "_Bool":
@@ -218,6 +221,8 @@ def type_name(ty, ptr=False, typing=False):
             return "float" if typing else "c_double"
         elif ty.names[0] == "size_t":
             return "int" if typing else "c_size_t"
+        elif ty.names[0] == "ptrdiff_t":
+            return "int" if typing else "c_ssize_t"
         elif ty.names[0] == "char":
             return "c_char"
         elif ty.names[0] == "int":

tests/component/test_component.py

@@ -0,0 +1,79 @@
+import unittest
+import tempfile
+
+from wasmtime import *
+from wasmtime.component import Component, ExportIndex
+
+class TestComponent(unittest.TestCase):
+    def test_smoke(self):
+        Component(Engine(), '(component)')
+        Component(Engine(), bytes(b'\0asm\x0d\0\x01\0'))
+        Component(Engine(), bytearray(b'\0asm\x0d\0\x01\0'))
+
+        with self.assertRaises(WasmtimeError):
+            Component(Engine(), '(component2)')
+        with self.assertRaises(WasmtimeError):
+            Component(Engine(), bytes(b'\0asm\x01\0\0\0'))
+
+    def test_invalid(self):
+        with self.assertRaises(TypeError):
+            Component(1, b'')  # type: ignore
+        with self.assertRaises(TypeError):
+            Component(Engine(), 2)  # type: ignore
+        with self.assertRaises(WasmtimeError):
+            Component(Engine(), b'')
+        with self.assertRaises(WasmtimeError):
+            Component(Engine(), b'\x00')
+
+    def test_serialize(self):
+        engine = Engine()
+        component = Component(engine, '(component)')
+        encoded = component.serialize()
+        component = Component.deserialize(engine, encoded)
+        with tempfile.TemporaryDirectory() as d:
+            path = d + '/component.bin'
+            with open(path, 'wb') as f:
+                f.write(encoded)
+            component = Component.deserialize_file(engine, path)
+
+            # Run the destructor for `Component` which has an mmap to the file
+            # which prevents deletion on Windows.
+            del component
+
+    def test_exports(self):
+        engine = Engine()
+
+        c = Component(engine, '(component)')
+        self.assertIsNone(c.get_export_index('foo'))
+        self.assertIsNone(c.get_export_index('foo', instance = None))
+
+        c = Component(engine, """
+            (component
+                (core module (export "foo"))
+            )
+        """)
+        foo = c.get_export_index('foo')
+        self.assertIsNotNone(foo)
+        self.assertIsNone(c.get_export_index('foo', instance = foo))
+        self.assertIsInstance(foo, ExportIndex)
+
+        c = Component(engine, """
+            (component
+                (core module $a)
+                (instance (export "x")
+                    (export "m" (core module $a))
+                )
+            )
+        """)
+        self.assertIsNotNone(c.get_export_index('x'))
+        self.assertIsNotNone(c.get_export_index('m', instance = c.get_export_index('x')))
+
+        c2 = Component(engine, """
+            (component
+                (core module $a)
+                (instance (export "x")
+                    (export "m" (core module $a))
+                )
+            )
+        """)
+        self.assertIsNone(c2.get_export_index('m', instance = c.get_export_index('x')))