All exceptions are now modified with extend_exception! macro

Author: sobolevn

Lib/test/exception_hierarchy.txt

@@ -42,7 +42,6 @@ BaseException
       |    +-- NotImplementedError
       |    +-- RecursionError
       +-- SyntaxError
-      |    +-- TargetScopeError
       |    +-- IndentationError
       |         +-- TabError
       +-- SystemError

derive/src/lib.rs

@@ -41,6 +41,24 @@ pub fn pyclass(attr: TokenStream, item: TokenStream) -> TokenStream {
     result_to_tokens(pyclass::impl_pyclass(attr, item))
 }
 
+/// This macro serves a goal of generating multiple
+/// `BaseException` / `Exception`
+/// subtypes in a uniform and convenient manner.
+/// It looks like `SimpleExtendsException` in `CPython`.
+/// https://github.com/python/cpython/blob/main/Objects/exceptions.c
+///
+/// We need `ctx` to be ready to add
+/// `properties` / `custom` constructors / slots / methods etc.
+/// So, we use `extend_class!` macro as the second
+/// step in exception type definition.
+#[proc_macro]
+pub fn define_exception(input: TokenStream) -> TokenStream {
+    let exc_def = parse_macro_input!(input as pyclass::PyExceptionDef);
+    result_to_tokens(pyclass::impl_define_exception(exc_def))
+}
+
+/// Helper macro to define `Exception` types.
+/// More-or-less is an alias to `pyclass` macro.
 #[proc_macro_attribute]
 pub fn pyexception(attr: TokenStream, item: TokenStream) -> TokenStream {
     let attr = parse_macro_input!(attr as AttributeArgs);

derive/src/pyclass.rs

@@ -6,8 +6,10 @@ use crate::util::{
 use proc_macro2::TokenStream;
 use quote::{quote, quote_spanned, ToTokens};
 use std::collections::HashMap;
+use syn::parse::{Parse, ParseStream, Result as ParsingResult};
 use syn::{
-    parse_quote, spanned::Spanned, Attribute, AttributeArgs, Ident, Item, Meta, NestedMeta, Result,
+    parse_quote, spanned::Spanned, Attribute, AttributeArgs, Ident, Item, LitStr, Meta, NestedMeta,
+    Result, Token,
 };
 use syn_ext::ext::*;
 
@@ -288,6 +290,71 @@ pub(crate) fn impl_pyexception(
     Ok(ret)
 }
 
+pub(crate) fn impl_define_exception(
+    exc_def: PyExceptionDef,
+) -> std::result::Result<TokenStream, Diagnostic> {
+    let PyExceptionDef {
+        class_name,
+        base_class,
+        ctx_name,
+        docs,
+        tp_new,
+        init,
+    } = exc_def;
+
+    // We need this method, because of how `CPython` copies `__new__`
+    // from `BaseException` in `SimpleExtendsException` macro.
+    // See: `BaseException_new`
+    let tp_new_slot = match tp_new {
+        Some(tp_call) => quote! { #tp_call(cls, args, vm) },
+        None => quote! { #base_class::tp_new(cls, args, vm) },
+    };
+
+    // We need this method, because of how `CPython` copies `__init__`
+    // from `BaseException` in `SimpleExtendsException` macro.
+    // See: `(initproc)BaseException_init`
+    let init_method = match init {
+        Some(init_def) => quote! { #init_def(zelf, args, vm) },
+        None => quote! { #base_class::init(zelf, args, vm) },
+    };
+
+    let ret = quote! {
+        #[pyexception(#class_name, #base_class)]
+        #[derive(Debug)]
+        #[doc = #docs]
+        struct #class_name {}
+
+        // We need this to make extend mechanism work:
+        impl PyValue for #class_name {
+            fn class(vm: &VirtualMachine) -> &PyTypeRef {
+                &vm.ctx.exceptions.#ctx_name
+            }
+        }
+
+        #[pyimpl(flags(BASETYPE, HAS_DICT))]
+        impl #class_name {
+            #[pyslot]
+            pub(crate) fn tp_new(
+                cls: PyTypeRef,
+                args: FuncArgs,
+                vm: &VirtualMachine,
+            ) -> PyResult {
+                #tp_new_slot
+            }
+
+            #[pymethod(magic)]
+            pub(crate) fn init(
+                zelf: PyRef<PyBaseException>,
+                args: FuncArgs,
+                vm: &VirtualMachine,
+            ) -> PyResult<()> {
+                #init_method
+            }
+        }
+    };
+    Ok(ret)
+}
+
 /// #[pymethod] and #[pyclassmethod]
 struct MethodItem {
     inner: ContentItemInner,
@@ -971,6 +1038,50 @@ where
     Ok((result, cfgs))
 }
 
+#[derive(Debug)]
+pub(crate) struct PyExceptionDef {
+    pub class_name: Ident,
+    pub base_class: Ident,
+    pub ctx_name: Ident,
+    pub docs: LitStr,
+
+    /// Holds optional `tp_new` slot to be used instead of a default one:
+    pub tp_new: Option<Ident>,
+    /// We also store `__init__` magic method, that can
+    pub init: Option<Ident>,
+}
+
+impl Parse for PyExceptionDef {
+    fn parse(input: ParseStream) -> ParsingResult<Self> {
+        let class_name: Ident = input.parse()?;
+        input.parse::<Token![,]>()?;
+
+        let base_class: Ident = input.parse()?;
+        input.parse::<Token![,]>()?;
+
+        let ctx_name: Ident = input.parse()?;
+        input.parse::<Token![,]>()?;
+
+        let docs: LitStr = input.parse()?;
+        input.parse::<Option<Token![,]>>()?;
+
+        let tp_new: Option<Ident> = input.parse()?;
+        input.parse::<Option<Token![,]>>()?;
+
+        let init: Option<Ident> = input.parse()?;
+        input.parse::<Option<Token![,]>>()?; // leading `,`
+
+        Ok(PyExceptionDef {
+            class_name,
+            base_class,
+            ctx_name,
+            docs,
+            tp_new,
+            init,
+        })
+    }
+}
+
 fn parse_vec_ident(
     attr: &[NestedMeta],
     item: &Item,

derive/src/pymodule.rs

@@ -109,7 +109,6 @@ fn new_module_item(
             inner: ContentItemInner { index, attr_name },
             pyattrs: pyattrs.unwrap_or_else(Vec::new),
         }),
-        "pyexception" => unreachable!("#[pyexception] {:?}", pyattrs.unwrap_or_else(Vec::new)),
         other => unreachable!("#[pymodule] doesn't accept #[{}]", other),
     }
 }

extra_tests/snippets/builtin_exceptions.py

@@ -1,3 +1,4 @@
+import builtins
 import platform
 import sys
 
@@ -161,37 +162,45 @@ class SubError(MyError):
 assert BaseException.__new__.__qualname__ == 'BaseException.__new__'
 assert BaseException.__init__.__qualname__ == 'BaseException.__init__'
 assert BaseException().__dict__ == {}
-assert BaseException.__doc__
 
 assert Exception.__new__.__qualname__ == 'Exception.__new__'
 assert Exception.__init__.__qualname__ == 'Exception.__init__'
 assert Exception().__dict__ == {}
-assert Exception.__doc__
 
 
 # Extends `BaseException`, simple:
 assert KeyboardInterrupt.__new__.__qualname__ == 'KeyboardInterrupt.__new__'
 assert KeyboardInterrupt.__init__.__qualname__ == 'KeyboardInterrupt.__init__'
 assert KeyboardInterrupt().__dict__ == {}
-assert KeyboardInterrupt.__doc__
 
 
 # Extends `Exception`, simple:
 assert TypeError.__new__.__qualname__ == 'TypeError.__new__'
 assert TypeError.__init__.__qualname__ == 'TypeError.__init__'
 assert TypeError().__dict__ == {}
-assert TypeError.__doc__
 
 
 # Extends `Exception`, complex:
 assert OSError.__new__.__qualname__ == 'OSError.__new__'
 assert OSError.__init__.__qualname__ == 'OSError.__init__'
 assert OSError().__dict__ == {}
-assert OSError.__doc__
 assert OSError.errno
 assert OSError.strerror
 assert OSError(1, 2).errno
 assert OSError(1, 2).strerror
 
+# Custom `__new__` and `__init__`:
 assert ImportError.__init__.__qualname__ == 'ImportError.__init__'
 assert ImportError(name='a').name == 'a'
+assert (
+    ModuleNotFoundError.__init__.__qualname__ == 'ModuleNotFoundError.__init__'
+)
+assert ModuleNotFoundError(name='a').name == 'a'
+
+
+# Check that all exceptions have string `__doc__`:
+for exc in filter(
+    lambda obj: isinstance(obj, BaseException),
+    vars(builtins).values(),
+):
+    assert isinstance(exc.__doc__, str)

vm/src/builtins/make_module.rs

@@ -988,7 +988,6 @@ pub fn make_module(vm: &VirtualMachine, module: PyObjectRef) {
         "NotImplementedError" => ctx.exceptions.not_implemented_error.clone(),
         "RecursionError" => ctx.exceptions.recursion_error.clone(),
         "SyntaxError" =>  ctx.exceptions.syntax_error.clone(),
-        "TargetScopeError" =>  ctx.exceptions.target_scope_error.clone(),
         "IndentationError" =>  ctx.exceptions.indentation_error.clone(),
         "TabError" =>  ctx.exceptions.tab_error.clone(),
         "SystemError" => ctx.exceptions.system_error.clone(),