Updated lower validation for Python/Ruby

I want to fix mozilla#1797 by cloning the object handle in lower().  However,
this presents an issue in the dynamic languages because they perform
various failable checks in lower(): type checks, bounds checks, etc.  If
the check fails, then the cloned handle will be leaked.

Prevent this by adding a `check()` method.  We do the check first then
once we get to `lower()`, nothing can fail.

uniffi_bindgen/src/bindings/python/gen_python/mod.rs

@@ -413,6 +413,10 @@ pub mod filters {
         Ok(format!("{}.lift", ffi_converter_name(as_ct)?))
     }
 
+    pub fn check_fn(as_ct: &impl AsCodeType) -> Result<String, askama::Error> {
+        Ok(format!("{}.check", ffi_converter_name(as_ct)?))
+    }
+
     pub fn lower_fn(as_ct: &impl AsCodeType) -> Result<String, askama::Error> {
         Ok(format!("{}.lower", ffi_converter_name(as_ct)?))
     }

uniffi_bindgen/src/bindings/python/templates/BooleanHelper.py

@@ -1,16 +1,20 @@
-class _UniffiConverterBool(_UniffiConverterPrimitive):
+class _UniffiConverterBool:
     @classmethod
     def check(cls, value):
         return not not value
 
+    @classmethod
+    def lower(cls, value):
+        return 1 if value else 0
+
+    @staticmethod
+    def lift(value):
+        return value != 0
+
     @classmethod
     def read(cls, buf):
         return cls.lift(buf.read_u8())
 
     @classmethod
-    def write_unchecked(cls, value, buf):
+    def write(cls, value, buf):
         buf.write_u8(value)
-
-    @staticmethod
-    def lift(value):
-        return value != 0

uniffi_bindgen/src/bindings/python/templates/BytesHelper.py

@@ -7,10 +7,13 @@ def read(buf):
         return buf.read(size)
 
     @staticmethod
-    def write(value, buf):
+    def check(value):
         try:
             memoryview(value)
         except TypeError:
             raise TypeError("a bytes-like object is required, not {!r}".format(type(value).__name__))
+
+    @staticmethod
+    def write(value, buf):
         buf.write_i32(len(value))
         buf.write(value)

uniffi_bindgen/src/bindings/python/templates/CallbackInterfaceRuntime.py

@@ -18,6 +18,10 @@ def read(cls, buf):
         handle = buf.read_u64()
         cls.lift(handle)
 
+    @classmethod
+    def check(cls, cb):
+        pass
+
     @classmethod
     def lower(cls, cb):
         handle = cls._handle_map.new_handle(cb)

uniffi_bindgen/src/bindings/python/templates/CustomType.py

@@ -17,6 +17,10 @@ def read(buf):
     def lift(value):
         return {{ builtin|ffi_converter_name }}.lift(value)
 
+    @staticmethod
+    def check(value):
+        return {{ builtin|ffi_converter_name }}.check(value)
+
     @staticmethod
     def lower(value):
         return {{ builtin|ffi_converter_name }}.lower(value)
@@ -51,6 +55,11 @@ def lift(value):
         builtin_value = {{ builtin|lift_fn }}(value)
         return {{ config.into_custom.render("builtin_value") }}
 
+    @staticmethod
+    def check(value):
+        builtin_value = {{ config.from_custom.render("value") }}
+        return {{ builtin|check_fn }}(builtin_value)
+
     @staticmethod
     def lower(value):
         builtin_value = {{ config.from_custom.render("value") }}

uniffi_bindgen/src/bindings/python/templates/DurationHelper.py

@@ -12,10 +12,14 @@ def read(buf):
         return datetime.timedelta(seconds=seconds, microseconds=microseconds)
 
     @staticmethod
-    def write(value, buf):
+    def check(value):
         seconds = value.seconds + value.days * 24 * 3600
-        nanoseconds = value.microseconds * 1000
         if seconds < 0:
             raise ValueError("Invalid duration, must be non-negative")
+
+    @staticmethod
+    def write(value, buf):
+        seconds = value.seconds + value.days * 24 * 3600
+        nanoseconds = value.microseconds * 1000
         buf.write_i64(seconds)
         buf.write_u32(nanoseconds)

uniffi_bindgen/src/bindings/python/templates/EnumTemplate.py

@@ -81,6 +81,25 @@ def read(buf):
         {%- endfor %}
         raise InternalError("Raw enum value doesn't match any cases")
 
+    @staticmethod
+    def check(value):
+        {%- if e.variants().is_empty() %}
+        pass
+        {%- else %}
+        {%- for variant in e.variants() %}
+        {%- if e.is_flat() %}
+        if value == {{ type_name }}.{{ variant.name()|enum_variant_py }}:
+        {%- else %}
+        if value.is_{{ variant.name()|var_name }}():
+        {%- endif %}
+            {%- for field in variant.fields() %}
+            {{ field|check_fn }}(value.{{ field.name()|var_name }})
+            {%- endfor %}
+            return
+        {%- endfor %}
+        {%- endif %}
+
+    @staticmethod
     def write(value, buf):
         {%- for variant in e.variants() %}
         {%- if e.is_flat() %}

uniffi_bindgen/src/bindings/python/templates/ErrorTemplate.py

@@ -59,6 +59,20 @@ def read(buf):
         {%- endfor %}
         raise InternalError("Raw enum value doesn't match any cases")
 
+    @staticmethod
+    def check(value):
+        {%- if e.variants().is_empty() %}
+        pass
+        {%- else %}
+        {%- for variant in e.variants() %}
+        if isinstance(value, {{ type_name }}.{{ variant.name()|class_name }}):
+            {%- for field in variant.fields() %}
+            {{ field|check_fn }}(value.{{ field.name()|var_name }})
+            {%- endfor %}
+            return
+        {%- endfor %}
+        {%- endif %}
+
     @staticmethod
     def write(value, buf):
         {%- for variant in e.variants() %}

uniffi_bindgen/src/bindings/python/templates/Float32Helper.py

@@ -4,5 +4,5 @@ def read(buf):
         return buf.read_float()
 
     @staticmethod
-    def write_unchecked(value, buf):
+    def write(value, buf):
         buf.write_float(value)

uniffi_bindgen/src/bindings/python/templates/Float64Helper.py

@@ -4,5 +4,5 @@ def read(buf):
         return buf.read_double()
 
     @staticmethod
-    def write_unchecked(value, buf):
+    def write(value, buf):
         buf.write_double(value)

uniffi_bindgen/src/bindings/python/templates/ForeignExecutorTemplate.py

@@ -12,9 +12,12 @@ class {{ ffi_converter_name }}:
     _handle_map = UniffiHandleMap()
 
     @classmethod
-    def lower(cls, eventloop):
+    def check(cls, eventloop):
         if not isinstance(eventloop, asyncio.BaseEventLoop):
             raise TypeError("_uniffi_executor_callback: Expected EventLoop instance")
+
+    @classmethod
+    def lower(cls, eventloop):
         return cls._handle_map.new_handle(eventloop)
 
     @classmethod

uniffi_bindgen/src/bindings/python/templates/Int16Helper.py

@@ -8,5 +8,5 @@ def read(buf):
         return buf.read_i16()
 
     @staticmethod
-    def write_unchecked(value, buf):
+    def write(value, buf):
         buf.write_i16(value)

uniffi_bindgen/src/bindings/python/templates/Int32Helper.py

@@ -8,5 +8,5 @@ def read(buf):
         return buf.read_i32()
 
     @staticmethod
-    def write_unchecked(value, buf):
+    def write(value, buf):
         buf.write_i32(value)

uniffi_bindgen/src/bindings/python/templates/Int64Helper.py

@@ -8,5 +8,5 @@ def read(buf):
         return buf.read_i64()
 
     @staticmethod
-    def write_unchecked(value, buf):
+    def write(value, buf):
         buf.write_i64(value)

uniffi_bindgen/src/bindings/python/templates/Int8Helper.py

@@ -8,5 +8,5 @@ def read(buf):
         return buf.read_i8()
 
     @staticmethod
-    def write_unchecked(value, buf):
+    def write(value, buf):
         buf.write_i8(value)

uniffi_bindgen/src/bindings/python/templates/MapTemplate.py

@@ -2,6 +2,12 @@
 {%- let value_ffi_converter = value_type|ffi_converter_name %}
 
 class {{ ffi_converter_name }}(_UniffiConverterRustBuffer):
+    @classmethod
+    def check(cls, items):
+        for (key, value) in items.items():
+            {{ key_ffi_converter }}.check(key)
+            {{ value_ffi_converter }}.check(value)
+
     @classmethod
     def write(cls, items, buf):
         buf.write_i32(len(items))

uniffi_bindgen/src/bindings/python/templates/ObjectTemplate.py

@@ -35,7 +35,6 @@ def _make_instance_(cls, handle):
     @classmethod
     def {{ cons.name()|fn_name }}(cls, {% call py::arg_list_decl(cons) %}):
         {%- call py::setup_args_extra_indent(cons) %}
-        # Call the (fallible) function before creating any half-baked object instances.
         uniffi_handle = {% call py::to_ffi_call(cons) %}
         return cls._make_instance_(uniffi_handle)
 {% endfor %}
@@ -83,6 +82,15 @@ class {{ ffi_converter_name }}:
     def lift(value: UniffiHandle):
         return {{ impl_name }}._make_instance_(value)
 
+    @staticmethod
+    def check(value: {{ type_name }}):
+        {%- if obj.is_trait_interface() %}
+        pass
+        {%- else %}
+        if not isinstance(value, {{ impl_name }}):
+            raise TypeError("Expected {{ impl_name }} instance, {} found".format(type(value).__name__))
+        {%- endif %}
+
     @staticmethod
     def lower(value: {{ type_name }}):
         {%- match obj.imp() %}

uniffi_bindgen/src/bindings/python/templates/OptionalTemplate.py

@@ -1,6 +1,11 @@
 {%- let inner_ffi_converter = inner_type|ffi_converter_name %}
 
 class {{ ffi_converter_name }}(_UniffiConverterRustBuffer):
+    @classmethod
+    def check(cls, value):
+        if value is not None:
+            {{ inner_ffi_converter }}.check(value)
+
     @classmethod
     def write(cls, value, buf):
         if value is None:

uniffi_bindgen/src/bindings/python/templates/RecordTemplate.py

@@ -42,6 +42,16 @@ def read(buf):
             {%- endfor %}
         )
 
+    @staticmethod
+    def check(value):
+        {%- if rec.fields().is_empty() %}
+        pass
+        {%- else %}
+        {%- for field in rec.fields() %}
+        {{ field|check_fn }}(value.{{ field.name()|var_name }})
+        {%- endfor %}
+        {%- endif %}
+
     @staticmethod
     def write(value, buf):
         {%- for field in rec.fields() %}

uniffi_bindgen/src/bindings/python/templates/RustBufferHelper.py

@@ -1,25 +1,13 @@
 # Types conforming to `_UniffiConverterPrimitive` pass themselves directly over the FFI.
 class _UniffiConverterPrimitive:
-    @classmethod
-    def check(cls, value):
-        return value
-
     @classmethod
     def lift(cls, value):
         return value
-
+ 
     @classmethod
     def lower(cls, value):
-        return cls.lowerUnchecked(cls.check(value))
-
-    @classmethod
-    def lowerUnchecked(cls, value):
         return value
 
-    @classmethod
-    def write(cls, value, buf):
-        cls.write_unchecked(cls.check(value), buf)
-
 class _UniffiConverterPrimitiveInt(_UniffiConverterPrimitive):
     @classmethod
     def check(cls, value):
@@ -31,7 +19,6 @@ def check(cls, value):
             raise TypeError("__index__ returned non-int (type {})".format(type(value).__name__))
         if not cls.VALUE_MIN <= value < cls.VALUE_MAX:
             raise ValueError("{} requires {} <= value < {}".format(cls.CLASS_NAME, cls.VALUE_MIN, cls.VALUE_MAX))
-        return super().check(value)
 
 class _UniffiConverterPrimitiveFloat(_UniffiConverterPrimitive):
     @classmethod
@@ -42,7 +29,6 @@ def check(cls, value):
             raise TypeError("must be real number, not {}".format(type(value).__name__))
         if not isinstance(value, float):
             raise TypeError("__float__ returned non-float (type {})".format(type(value).__name__))
-        return super().check(value)
 
 # Helper class for wrapper types that will always go through a _UniffiRustBuffer.
 # Classes should inherit from this and implement the `read` and `write` static methods.

uniffi_bindgen/src/bindings/python/templates/SequenceTemplate.py

@@ -1,6 +1,11 @@
 {%- let inner_ffi_converter = inner_type|ffi_converter_name %}
 
 class {{ ffi_converter_name}}(_UniffiConverterRustBuffer):
+    @classmethod
+    def check(cls, value):
+        for item in value:
+            {{ inner_ffi_converter }}.check(item)
+
     @classmethod
     def write(cls, value, buf):
         items = len(value)

uniffi_bindgen/src/bindings/python/templates/StringHelper.py

@@ -15,7 +15,6 @@ def read(buf):
 
     @staticmethod
     def write(value, buf):
-        value = _UniffiConverterString.check(value)
         utf8_bytes = value.encode("utf-8")
         buf.write_i32(len(utf8_bytes))
         buf.write(utf8_bytes)
@@ -27,7 +26,6 @@ def lift(buf):
 
     @staticmethod
     def lower(value):
-        value = _UniffiConverterString.check(value)
         with _UniffiRustBuffer.alloc_with_builder() as builder:
             builder.write(value.encode("utf-8"))
             return builder.finalize()

uniffi_bindgen/src/bindings/python/templates/TimestampHelper.py

@@ -17,6 +17,10 @@ def read(buf):
         else:
             return datetime.datetime.fromtimestamp(0, tz=datetime.timezone.utc) - datetime.timedelta(seconds=-seconds, microseconds=microseconds)
 
+    @staticmethod
+    def check(value):
+        pass
+
     @staticmethod
     def write(value, buf):
         if value >= datetime.datetime.fromtimestamp(0, datetime.timezone.utc):

uniffi_bindgen/src/bindings/python/templates/TopLevelFunctionTemplate.py

@@ -1,6 +1,7 @@
 {%- if func.is_async() %}
 
 def {{ func.name()|fn_name }}({%- call py::arg_list_decl(func) -%}):
+    {%- call py::setup_args(func) %}
     return _uniffi_rust_call_async(
         _UniffiLib.{{ func.ffi_func().name() }}({% call py::arg_list_lowered(func) %}),
         _UniffiLib.{{func.ffi_rust_future_poll(ci) }},

uniffi_bindgen/src/bindings/python/templates/UInt16Helper.py

@@ -8,5 +8,5 @@ def read(buf):
         return buf.read_u16()
 
     @staticmethod
-    def write_unchecked(value, buf):
+    def write(value, buf):
         buf.write_u16(value)

uniffi_bindgen/src/bindings/python/templates/UInt32Helper.py

@@ -8,5 +8,5 @@ def read(buf):
         return buf.read_u32()
 
     @staticmethod
-    def write_unchecked(value, buf):
+    def write(value, buf):
         buf.write_u32(value)

uniffi_bindgen/src/bindings/python/templates/UInt64Helper.py

@@ -8,5 +8,5 @@ def read(buf):
         return buf.read_u64()
 
     @staticmethod
-    def write_unchecked(value, buf):
+    def write(value, buf):
         buf.write_u64(value)

uniffi_bindgen/src/bindings/python/templates/UInt8Helper.py

@@ -8,5 +8,5 @@ def read(buf):
         return buf.read_u8()
 
     @staticmethod
-    def write_unchecked(value, buf):
+    def write(value, buf):
         buf.write_u8(value)