Auto merge of #55780 - ogoffart:span_source_text, r=petrochenkov

Introduce proc_macro::Span::source_text

A function to extract the actual source behind a Span.

Background: I would like to use `syn` in a `build.rs` script to parse the rust code, and extract part of the source code. However, `syn` only gives access to proc_macro2::Span, and i would like to get the source code behind that.
I opened an issue on proc_macro2 bug tracker for this feature https://github.com/alexcrichton/proc-macro2/issues/110  and @alexcrichton said the feature should first go upstream in proc_macro.  So there it is!

Since most of the Span API is unstable anyway, this is guarded by the same `proc_macro_span` feature as everything else.
This commit is contained in:
bors 2019-03-27 08:58:40 +00:00
commit c5fb4d0d2f
5 changed files with 59 additions and 2 deletions

View File

@ -155,6 +155,7 @@ macro_rules! with_api {
fn end($self: $S::Span) -> LineColumn;
fn join($self: $S::Span, other: $S::Span) -> Option<$S::Span>;
fn resolved_at($self: $S::Span, at: $S::Span) -> $S::Span;
fn source_text($self: $S::Span) -> Option<String>;
},
}
};

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@ -333,6 +333,18 @@ impl Span {
self.0 == other.0
}
/// Returns the source text behind a span. This preserves the original source
/// code, including spaces and comments. It only returns a result if the span
/// corresponds to real source code.
///
/// Note: The observable result of a macro should only rely on the tokens and
/// not on this source text. The result of this function is a best effort to
/// be used for diagnostics only.
#[unstable(feature = "proc_macro_span", issue = "54725")]
pub fn source_text(&self) -> Option<String> {
self.0.source_text()
}
diagnostic_method!(error, Level::Error);
diagnostic_method!(warning, Level::Warning);
diagnostic_method!(note, Level::Note);

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@ -740,4 +740,7 @@ impl server::Span for Rustc<'_> {
fn resolved_at(&mut self, span: Self::Span, at: Self::Span) -> Self::Span {
span.with_ctxt(at.ctxt())
}
fn source_text(&mut self, span: Self::Span) -> Option<String> {
self.sess.source_map().span_to_snippet(span).ok()
}
}

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@ -33,3 +33,14 @@ pub fn assert_source_file(input: TokenStream) -> TokenStream {
"".parse().unwrap()
}
#[proc_macro]
pub fn macro_stringify(input: TokenStream) -> TokenStream {
let mut tokens = input.into_iter();
let first_span = tokens.next().expect("first token").span();
let last_span = tokens.last().map(|x| x.span()).unwrap_or(first_span);
let span = first_span.join(last_span).expect("joined span");
let src = span.source_text().expect("source_text");
TokenTree::Literal(Literal::string(&src)).into()
}

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@ -3,12 +3,14 @@
// ignore-pretty
#![feature(proc_macro_hygiene)]
#[macro_use]
extern crate span_test_macros;
extern crate span_api_tests;
use span_api_tests::{reemit, assert_fake_source_file, assert_source_file};
use span_api_tests::{reemit, assert_fake_source_file, assert_source_file, macro_stringify};
macro_rules! say_hello {
($macname:ident) => ( $macname! { "Hello, world!" })
@ -28,4 +30,32 @@ reemit! {
assert_source_file! { "Hello, world!" }
}
fn main() {}
fn main() {
let s = macro_stringify!(Hello, world!);
assert_eq!(s, "Hello, world!");
assert_eq!(macro_stringify!(Hello, world!), "Hello, world!");
assert_eq!(reemit_legacy!(macro_stringify!(Hello, world!)), "Hello, world!");
reemit_legacy!(assert_eq!(macro_stringify!(Hello, world!), "Hello, world!"));
// reemit change the span to be that of the call site
assert_eq!(
reemit!(macro_stringify!(Hello, world!)),
"reemit!(macro_stringify!(Hello, world!))"
);
let r = "reemit!(assert_eq!(macro_stringify!(Hello, world!), r));";
reemit!(assert_eq!(macro_stringify!(Hello, world!), r));
assert_eq!(macro_stringify!(
Hello,
world!
), "Hello,\n world!");
assert_eq!(macro_stringify!(Hello, /*world */ !), "Hello, /*world */ !");
assert_eq!(macro_stringify!(
Hello,
// comment
world!
), "Hello,\n // comment\n world!");
assert_eq!(say_hello! { macro_stringify }, "\"Hello, world!\"");
assert_eq!(say_hello_extern! { macro_stringify }, "\"Hello, world!\"");
}