Merge pull request RustPython#845 from RustPython/coolreader18/proc-macro-span-errors

Target rustpython_derive errors at specific source spans

Author: coolreader18

derive/src/error.rs

@@ -0,0 +1,158 @@
+// Taken from https://github.com/rustwasm/wasm-bindgen/blob/master/crates/backend/src/error.rs
+//
+// Copyright (c) 2014 Alex Crichton
+//
+// Permission is hereby granted, free of charge, to any
+// person obtaining a copy of this software and associated
+// documentation files (the "Software"), to deal in the
+// Software without restriction, including without
+// limitation the rights to use, copy, modify, merge,
+// publish, distribute, sublicense, and/or sell copies of
+// the Software, and to permit persons to whom the Software
+// is furnished to do so, subject to the following
+// conditions:
+//
+// The above copyright notice and this permission notice
+// shall be included in all copies or substantial portions
+// of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF
+// ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
+// TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
+// PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT
+// SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+// CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR
+// IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+// DEALINGS IN THE SOFTWARE.
+#![allow(dead_code)]
+
+use proc_macro2::*;
+use quote::{ToTokens, TokenStreamExt};
+use syn::parse::Error;
+
+macro_rules! err_span {
+    ($span:expr, $($msg:tt)*) => (
+        $crate::Diagnostic::spanned_error(&$span, format!($($msg)*))
+    )
+}
+
+macro_rules! bail_span {
+    ($($t:tt)*) => (
+        return Err(err_span!($($t)*).into())
+    )
+}
+
+macro_rules! push_err_span {
+    ($diagnostics:expr, $($t:tt)*) => {
+        $diagnostics.push(err_span!($($t)*))
+    };
+}
+
+#[derive(Debug)]
+pub struct Diagnostic {
+    inner: Repr,
+}
+
+#[derive(Debug)]
+enum Repr {
+    Single {
+        text: String,
+        span: Option<(Span, Span)>,
+    },
+    SynError(Error),
+    Multi {
+        diagnostics: Vec<Diagnostic>,
+    },
+}
+
+impl Diagnostic {
+    pub fn error<T: Into<String>>(text: T) -> Diagnostic {
+        Diagnostic {
+            inner: Repr::Single {
+                text: text.into(),
+                span: None,
+            },
+        }
+    }
+
+    pub fn span_error<T: Into<String>>(span: Span, text: T) -> Diagnostic {
+        Diagnostic {
+            inner: Repr::Single {
+                text: text.into(),
+                span: Some((span, span)),
+            },
+        }
+    }
+
+    pub fn spanned_error<T: Into<String>>(node: &ToTokens, text: T) -> Diagnostic {
+        Diagnostic {
+            inner: Repr::Single {
+                text: text.into(),
+                span: extract_spans(node),
+            },
+        }
+    }
+
+    pub fn from_vec(diagnostics: Vec<Diagnostic>) -> Result<(), Diagnostic> {
+        if diagnostics.len() == 0 {
+            Ok(())
+        } else {
+            Err(Diagnostic {
+                inner: Repr::Multi { diagnostics },
+            })
+        }
+    }
+
+    #[allow(unconditional_recursion)]
+    pub fn panic(&self) -> ! {
+        match &self.inner {
+            Repr::Single { text, .. } => panic!("{}", text),
+            Repr::SynError(error) => panic!("{}", error),
+            Repr::Multi { diagnostics } => diagnostics[0].panic(),
+        }
+    }
+}
+
+impl From<Error> for Diagnostic {
+    fn from(err: Error) -> Diagnostic {
+        Diagnostic {
+            inner: Repr::SynError(err),
+        }
+    }
+}
+
+fn extract_spans(node: &ToTokens) -> Option<(Span, Span)> {
+    let mut t = TokenStream::new();
+    node.to_tokens(&mut t);
+    let mut tokens = t.into_iter();
+    let start = tokens.next().map(|t| t.span());
+    let end = tokens.last().map(|t| t.span());
+    start.map(|start| (start, end.unwrap_or(start)))
+}
+
+impl ToTokens for Diagnostic {
+    fn to_tokens(&self, dst: &mut TokenStream) {
+        match &self.inner {
+            Repr::Single { text, span } => {
+                let cs2 = (Span::call_site(), Span::call_site());
+                let (start, end) = span.unwrap_or(cs2);
+                dst.append(Ident::new("compile_error", start));
+                dst.append(Punct::new('!', Spacing::Alone));
+                let mut message = TokenStream::new();
+                message.append(Literal::string(text));
+                let mut group = Group::new(Delimiter::Brace, message);
+                group.set_span(end);
+                dst.append(group);
+            }
+            Repr::Multi { diagnostics } => {
+                for diagnostic in diagnostics {
+                    diagnostic.to_tokens(dst);
+                }
+            }
+            Repr::SynError(err) => {
+                err.to_compile_error().to_tokens(dst);
+            }
+        }
+    }
+}

derive/src/lib.rs

@@ -1,10 +1,22 @@
 extern crate proc_macro;
 
+#[macro_use]
+mod error;
+mod from_args;
+mod pyclass;
+
+use error::Diagnostic;
 use proc_macro::TokenStream;
+use proc_macro2::TokenStream as TokenStream2;
+use quote::ToTokens;
 use syn::{parse_macro_input, AttributeArgs, DeriveInput, Item};
 
-mod from_args;
-mod pyclass;
+fn result_to_tokens(result: Result<TokenStream2, Diagnostic>) -> TokenStream {
+    match result {
+        Ok(tokens) => tokens.into(),
+        Err(diagnostic) => diagnostic.into_token_stream().into(),
+    }
+}
 
 #[proc_macro_derive(FromArgs, attributes(pyarg))]
 pub fn derive_from_args(input: TokenStream) -> TokenStream {
@@ -17,12 +29,12 @@ pub fn derive_from_args(input: TokenStream) -> TokenStream {
 pub fn pyclass(attr: TokenStream, item: TokenStream) -> TokenStream {
     let attr = parse_macro_input!(attr as AttributeArgs);
     let item = parse_macro_input!(item as Item);
-    pyclass::impl_pyclass(attr, item).into()
+    result_to_tokens(pyclass::impl_pyclass(attr, item))
 }
 
 #[proc_macro_attribute]
 pub fn pyimpl(attr: TokenStream, item: TokenStream) -> TokenStream {
     let attr = parse_macro_input!(attr as AttributeArgs);
     let item = parse_macro_input!(item as Item);
-    pyclass::impl_pyimpl(attr, item).into()
+    result_to_tokens(pyclass::impl_pyimpl(attr, item))
 }