Strip frontmatter in fewer places

fmease · fmease · commit 50f74e513d17 · 2025-09-08T20:05:29.000+02:00
diff --git a/compiler/rustc_builtin_macros/src/source_util.rs b/compiler/rustc_builtin_macros/src/source_util.rs
@@ -13,6 +13,7 @@ use rustc_expand::base::{
 };
 use rustc_expand::module::DirOwnership;
 use rustc_lint_defs::BuiltinLintDiag;
+use rustc_parse::lexer::StripTokens;
 use rustc_parse::parser::{ForceCollect, Parser};
 use rustc_parse::{new_parser_from_file, unwrap_or_emit_fatal, utf8_error};
 use rustc_session::lint::builtin::INCOMPLETE_INCLUDE;
@@ -126,7 +127,16 @@ pub(crate) fn expand_include<'cx>(
             return ExpandResult::Ready(DummyResult::any(sp, guar));
         }
     };
-    let p = unwrap_or_emit_fatal(new_parser_from_file(cx.psess(), &file, Some(sp)));
+    // FIXME(frontmatter): Consider stripping frontmatter in a future edition. We can't strip them
+    // in the current edition since that would be breaking.
+    // See also <https://github.com/rust-lang/rust/issues/145945>.
+    // Alternatively, stop stripping shebangs here, too, if T-lang and crater approve.
+    let p = unwrap_or_emit_fatal(new_parser_from_file(
+        cx.psess(),
+        &file,
+        StripTokens::Shebang,
+        Some(sp),
+    ));
 
     // If in the included file we have e.g., `mod bar;`,
     // then the path of `bar.rs` should be relative to the directory of `file`.
diff --git a/compiler/rustc_driver_impl/src/lib.rs b/compiler/rustc_driver_impl/src/lib.rs
@@ -51,6 +51,7 @@ use rustc_lint::unerased_lint_store;
 use rustc_metadata::creader::MetadataLoader;
 use rustc_metadata::locator;
 use rustc_middle::ty::TyCtxt;
+use rustc_parse::lexer::StripTokens;
 use rustc_parse::{new_parser_from_file, new_parser_from_source_str, unwrap_or_emit_fatal};
 use rustc_session::config::{
     CG_OPTIONS, CrateType, ErrorOutputType, Input, OptionDesc, OutFileName, OutputType, Sysroot,
@@ -1288,10 +1289,15 @@ fn warn_on_confusing_output_filename_flag(
 
 fn parse_crate_attrs<'a>(sess: &'a Session) -> PResult<'a, ast::AttrVec> {
     let mut parser = unwrap_or_emit_fatal(match &sess.io.input {
-        Input::File(file) => new_parser_from_file(&sess.psess, file, None),
-        Input::Str { name, input } => {
-            new_parser_from_source_str(&sess.psess, name.clone(), input.clone())
+        Input::File(file) => {
+            new_parser_from_file(&sess.psess, file, StripTokens::ShebangAndFrontmatter, None)
         }
+        Input::Str { name, input } => new_parser_from_source_str(
+            &sess.psess,
+            name.clone(),
+            input.clone(),
+            StripTokens::ShebangAndFrontmatter,
+        ),
     });
     parser.parse_inner_attributes()
 }
diff --git a/compiler/rustc_expand/src/module.rs b/compiler/rustc_expand/src/module.rs
@@ -4,6 +4,7 @@ use std::path::{self, Path, PathBuf};
 use rustc_ast::{AttrVec, Attribute, Inline, Item, ModSpans};
 use rustc_attr_parsing::validate_attr;
 use rustc_errors::{Diag, ErrorGuaranteed};
+use rustc_parse::lexer::StripTokens;
 use rustc_parse::{exp, new_parser_from_file, unwrap_or_emit_fatal};
 use rustc_session::Session;
 use rustc_session::parse::ParseSess;
@@ -67,8 +68,12 @@ pub(crate) fn parse_external_mod(
         }
 
         // Actually parse the external file as a module.
-        let mut parser =
-            unwrap_or_emit_fatal(new_parser_from_file(&sess.psess, &mp.file_path, Some(span)));
+        let mut parser = unwrap_or_emit_fatal(new_parser_from_file(
+            &sess.psess,
+            &mp.file_path,
+            StripTokens::ShebangAndFrontmatter,
+            Some(span),
+        ));
         let (inner_attrs, items, inner_span) =
             parser.parse_mod(exp!(Eof)).map_err(|err| ModError::ParserError(err))?;
         attrs.extend(inner_attrs);
diff --git a/compiler/rustc_expand/src/proc_macro_server.rs b/compiler/rustc_expand/src/proc_macro_server.rs
@@ -8,7 +8,7 @@ use rustc_ast::util::literal::escape_byte_str_symbol;
 use rustc_ast_pretty::pprust;
 use rustc_data_structures::fx::FxHashMap;
 use rustc_errors::{Diag, ErrorGuaranteed, MultiSpan, PResult};
-use rustc_parse::lexer::nfc_normalize;
+use rustc_parse::lexer::{StripTokens, nfc_normalize};
 use rustc_parse::parser::Parser;
 use rustc_parse::{exp, new_parser_from_source_str, source_str_to_stream, unwrap_or_emit_fatal};
 use rustc_proc_macro::bridge::{
@@ -485,8 +485,13 @@ impl server::FreeFunctions for Rustc<'_, '_> {
 
     fn literal_from_str(&mut self, s: &str) -> Result<Literal<Self::Span, Self::Symbol>, ()> {
         let name = FileName::proc_macro_source_code(s);
-        let mut parser =
-            unwrap_or_emit_fatal(new_parser_from_source_str(self.psess(), name, s.to_owned()));
+
+        let mut parser = unwrap_or_emit_fatal(new_parser_from_source_str(
+            self.psess(),
+            name,
+            s.to_owned(),
+            StripTokens::Nothing,
+        ));
 
         let first_span = parser.token.span.data();
         let minus_present = parser.eat(exp!(Minus));
diff --git a/compiler/rustc_interface/src/interface.rs b/compiler/rustc_interface/src/interface.rs
@@ -13,7 +13,8 @@ use rustc_lint::LintStore;
 use rustc_middle::ty;
 use rustc_middle::ty::CurrentGcx;
 use rustc_middle::util::Providers;
-use rustc_parse::new_parser_from_simple_source_str;
+use rustc_parse::lexer::StripTokens;
+use rustc_parse::new_parser_from_source_str;
 use rustc_parse::parser::attr::AllowLeadingUnsafe;
 use rustc_query_impl::QueryCtxt;
 use rustc_query_system::query::print_query_stack;
@@ -68,7 +69,8 @@ pub(crate) fn parse_cfg(dcx: DiagCtxtHandle<'_>, cfgs: Vec<String>) -> Cfg {
                 };
             }
 
-            match new_parser_from_simple_source_str(&psess, filename, s.to_string()) {
+            match new_parser_from_source_str(&psess, filename, s.to_string(), StripTokens::Nothing)
+            {
                 Ok(mut parser) => match parser.parse_meta_item(AllowLeadingUnsafe::No) {
                     Ok(meta_item) if parser.token == token::Eof => {
                         if meta_item.path.segments.len() != 1 {
@@ -166,13 +168,15 @@ pub(crate) fn parse_check_cfg(dcx: DiagCtxtHandle<'_>, specs: Vec<String>) -> Ch
             error!("expected `cfg(name, values(\"value1\", \"value2\", ... \"valueN\"))`")
         };
 
-        let mut parser = match new_parser_from_simple_source_str(&psess, filename, s.to_string()) {
-            Ok(parser) => parser,
-            Err(errs) => {
-                errs.into_iter().for_each(|err| err.cancel());
-                expected_error();
-            }
-        };
+        let mut parser =
+            match new_parser_from_source_str(&psess, filename, s.to_string(), StripTokens::Nothing)
+            {
+                Ok(parser) => parser,
+                Err(errs) => {
+                    errs.into_iter().for_each(|err| err.cancel());
+                    expected_error();
+                }
+            };
 
         let meta_item = match parser.parse_meta_item(AllowLeadingUnsafe::No) {
             Ok(meta_item) if parser.token == token::Eof => meta_item,
diff --git a/compiler/rustc_interface/src/passes.rs b/compiler/rustc_interface/src/passes.rs
@@ -27,6 +27,7 @@ use rustc_middle::arena::Arena;
 use rustc_middle::dep_graph::DepsType;
 use rustc_middle::ty::{self, CurrentGcx, GlobalCtxt, RegisteredTools, TyCtxt};
 use rustc_middle::util::Providers;
+use rustc_parse::lexer::StripTokens;
 use rustc_parse::{new_parser_from_file, new_parser_from_source_str, unwrap_or_emit_fatal};
 use rustc_passes::{abi_test, input_stats, layout_test};
 use rustc_resolve::{Resolver, ResolverOutputs};
@@ -51,10 +52,18 @@ pub fn parse<'a>(sess: &'a Session) -> ast::Crate {
     let mut krate = sess
         .time("parse_crate", || {
             let mut parser = unwrap_or_emit_fatal(match &sess.io.input {
-                Input::File(file) => new_parser_from_file(&sess.psess, file, None),
-                Input::Str { input, name } => {
-                    new_parser_from_source_str(&sess.psess, name.clone(), input.clone())
-                }
+                Input::File(file) => new_parser_from_file(
+                    &sess.psess,
+                    file,
+                    StripTokens::ShebangAndFrontmatter,
+                    None,
+                ),
+                Input::Str { input, name } => new_parser_from_source_str(
+                    &sess.psess,
+                    name.clone(),
+                    input.clone(),
+                    StripTokens::ShebangAndFrontmatter,
+                ),
             });
             parser.parse_crate_mod()
         })
diff --git a/compiler/rustc_parse/src/lexer/mod.rs b/compiler/rustc_parse/src/lexer/mod.rs
@@ -45,7 +45,7 @@ pub(crate) struct UnmatchedDelim {
 }
 
 /// Which tokens should be stripped before lexing the tokens.
-pub(crate) enum StripTokens {
+pub enum StripTokens {
     /// Strip both shebang and frontmatter.
     ShebangAndFrontmatter,
     /// Strip the shebang but not frontmatter.
diff --git a/compiler/rustc_parse/src/lib.rs b/compiler/rustc_parse/src/lib.rs
@@ -54,29 +54,18 @@ pub fn unwrap_or_emit_fatal<T>(expr: Result<T, Vec<Diag<'_>>>) -> T {
     }
 }
 
-/// Creates a new parser from a source string. On failure, the errors must be consumed via
-/// `unwrap_or_emit_fatal`, `emit`, `cancel`, etc., otherwise a panic will occur when they are
-/// dropped.
-pub fn new_parser_from_source_str(
-    psess: &ParseSess,
-    name: FileName,
-    source: String,
-) -> Result<Parser<'_>, Vec<Diag<'_>>> {
-    let source_file = psess.source_map().new_source_file(name, source);
-    new_parser_from_source_file(psess, source_file, StripTokens::ShebangAndFrontmatter)
-}
-
-/// Creates a new parser from a simple (no shebang, no frontmatter) source string.
+/// Creates a new parser from a source string.
 ///
 /// On failure, the errors must be consumed via `unwrap_or_emit_fatal`, `emit`, `cancel`,
 /// etc., otherwise a panic will occur when they are dropped.
-pub fn new_parser_from_simple_source_str(
+pub fn new_parser_from_source_str(
     psess: &ParseSess,
     name: FileName,
     source: String,
+    strip_tokens: StripTokens,
 ) -> Result<Parser<'_>, Vec<Diag<'_>>> {
     let source_file = psess.source_map().new_source_file(name, source);
-    new_parser_from_source_file(psess, source_file, StripTokens::Nothing)
+    new_parser_from_source_file(psess, source_file, strip_tokens)
 }
 
 /// Creates a new parser from a filename. On failure, the errors must be consumed via
@@ -87,6 +76,7 @@ pub fn new_parser_from_simple_source_str(
 pub fn new_parser_from_file<'a>(
     psess: &'a ParseSess,
     path: &Path,
+    strip_tokens: StripTokens,
     sp: Option<Span>,
 ) -> Result<Parser<'a>, Vec<Diag<'a>>> {
     let sm = psess.source_map();
@@ -110,7 +100,7 @@ pub fn new_parser_from_file<'a>(
         }
         err.emit();
     });
-    new_parser_from_source_file(psess, source_file, StripTokens::ShebangAndFrontmatter)
+    new_parser_from_source_file(psess, source_file, strip_tokens)
 }
 
 pub fn utf8_error<E: EmissionGuarantee>(
@@ -172,20 +162,26 @@ fn new_parser_from_source_file(
     Ok(parser)
 }
 
+/// Given a source string, produces a sequence of token trees.
+///
+/// NOTE: This only strips shebangs, not frontmatter!
 pub fn source_str_to_stream(
     psess: &ParseSess,
     name: FileName,
     source: String,
     override_span: Option<Span>,
 ) -> Result<TokenStream, Vec<Diag<'_>>> {
     let source_file = psess.source_map().new_source_file(name, source);
-    // used mainly for `proc_macro` and the likes, not for our parsing purposes, so don't parse
-    // frontmatters as frontmatters, but for compatibility reason still strip the shebang
+    // FIXME(frontmatter): Consider stripping frontmatter in a future edition. We can't strip them
+    // in the current edition since that would be breaking.
+    // See also <https://github.com/rust-lang/rust/issues/145520>.
+    // Alternatively, stop stripping shebangs here, too, if T-lang and crater approve.
     source_file_to_stream(psess, source_file, override_span, StripTokens::Shebang)
 }
 
-/// Given a source file, produces a sequence of token trees. Returns any buffered errors from
-/// parsing the token stream.
+/// Given a source file, produces a sequence of token trees.
+///
+/// Returns any buffered errors from parsing the token stream.
 fn source_file_to_stream<'psess>(
     psess: &'psess ParseSess,
     source_file: Arc<SourceFile>,
diff --git a/compiler/rustc_parse/src/parser/tests.rs b/compiler/rustc_parse/src/parser/tests.rs
@@ -22,6 +22,7 @@ use rustc_span::{
 };
 use termcolor::WriteColor;
 
+use crate::lexer::StripTokens;
 use crate::parser::{ForceCollect, Parser};
 use crate::{new_parser_from_source_str, source_str_to_stream, unwrap_or_emit_fatal};
 
@@ -35,6 +36,7 @@ fn string_to_parser(psess: &ParseSess, source_str: String) -> Parser<'_> {
         psess,
         PathBuf::from("bogofile").into(),
         source_str,
+        StripTokens::Nothing,
     ))
 }
 
@@ -2240,7 +2242,7 @@ fn parse_item_from_source_str(
     source: String,
     psess: &ParseSess,
 ) -> PResult<'_, Option<Box<ast::Item>>> {
-    unwrap_or_emit_fatal(new_parser_from_source_str(psess, name, source))
+    unwrap_or_emit_fatal(new_parser_from_source_str(psess, name, source, StripTokens::Nothing))
         .parse_item(ForceCollect::No)
 }
 
@@ -2520,7 +2522,8 @@ fn ttdelim_span() {
         source: String,
         psess: &ParseSess,
     ) -> PResult<'_, Box<ast::Expr>> {
-        unwrap_or_emit_fatal(new_parser_from_source_str(psess, name, source)).parse_expr()
+        unwrap_or_emit_fatal(new_parser_from_source_str(psess, name, source, StripTokens::Nothing))
+            .parse_expr()
     }
 
     create_default_session_globals_then(|| {
diff --git a/src/librustdoc/clean/render_macro_matchers.rs b/src/librustdoc/clean/render_macro_matchers.rs
@@ -3,6 +3,7 @@ use rustc_ast::tokenstream::{TokenStream, TokenTree};
 use rustc_ast_pretty::pprust::PrintState;
 use rustc_ast_pretty::pprust::state::State as Printer;
 use rustc_middle::ty::TyCtxt;
+use rustc_parse::lexer::StripTokens;
 use rustc_session::parse::ParseSess;
 use rustc_span::symbol::{Ident, Symbol, kw};
 use rustc_span::{FileName, Span};
@@ -64,14 +65,18 @@ fn snippet_equal_to_token(tcx: TyCtxt<'_>, matcher: &TokenTree) -> Option<String
     // Create a Parser.
     let psess = ParseSess::new(rustc_driver::DEFAULT_LOCALE_RESOURCES.to_vec());
     let file_name = FileName::macro_expansion_source_code(&snippet);
-    let mut parser =
-        match rustc_parse::new_parser_from_source_str(&psess, file_name, snippet.clone()) {
-            Ok(parser) => parser,
-            Err(errs) => {
-                errs.into_iter().for_each(|err| err.cancel());
-                return None;
-            }
-        };
+    let mut parser = match rustc_parse::new_parser_from_source_str(
+        &psess,
+        file_name,
+        snippet.clone(),
+        StripTokens::Nothing,
+    ) {
+        Ok(parser) => parser,
+        Err(errs) => {
+            errs.into_iter().for_each(|err| err.cancel());
+            return None;
+        }
+    };
 
     // Reparse a single token tree.
     if parser.token == token::Eof {
diff --git a/src/librustdoc/doctest/make.rs b/src/librustdoc/doctest/make.rs
@@ -10,6 +10,7 @@ use rustc_ast::tokenstream::TokenTree;
 use rustc_ast::{self as ast, AttrStyle, HasAttrs, StmtKind};
 use rustc_errors::emitter::stderr_destination;
 use rustc_errors::{ColorConfig, DiagCtxtHandle};
+use rustc_parse::lexer::StripTokens;
 use rustc_parse::new_parser_from_source_str;
 use rustc_session::parse::ParseSess;
 use rustc_span::edition::{DEFAULT_EDITION, Edition};
@@ -468,14 +469,16 @@ fn parse_source(
     let dcx = DiagCtxt::new(Box::new(emitter)).disable_warnings();
     let psess = ParseSess::with_dcx(dcx, sm);
 
-    let mut parser = match new_parser_from_source_str(&psess, filename, wrapped_source) {
-        Ok(p) => p,
-        Err(errs) => {
-            errs.into_iter().for_each(|err| err.cancel());
-            reset_error_count(&psess);
-            return Err(());
-        }
-    };
+    // Don't strip any tokens; it wouldn't matter anyway because the source is wrapped in a function.
+    let mut parser =
+        match new_parser_from_source_str(&psess, filename, wrapped_source, StripTokens::Nothing) {
+            Ok(p) => p,
+            Err(errs) => {
+                errs.into_iter().for_each(|err| err.cancel());
+                reset_error_count(&psess);
+                return Err(());
+            }
+        };
 
     fn push_to_s(s: &mut String, source: &str, span: rustc_span::Span, prev_span_hi: &mut usize) {
         let extra_len = DOCTEST_CODE_WRAPPER.len();
diff --git a/src/tools/clippy/clippy_lints/src/doc/needless_doctest_main.rs b/src/tools/clippy/clippy_lints/src/doc/needless_doctest_main.rs
@@ -8,6 +8,7 @@ use rustc_ast::{CoroutineKind, Fn, FnRetTy, Item, ItemKind};
 use rustc_errors::emitter::HumanEmitter;
 use rustc_errors::{Diag, DiagCtxt};
 use rustc_lint::LateContext;
+use rustc_parse::lexer::StripTokens;
 use rustc_parse::new_parser_from_source_str;
 use rustc_parse::parser::ForceCollect;
 use rustc_session::parse::ParseSess;
@@ -49,7 +50,7 @@ pub fn check(
                 let sm = Arc::new(SourceMap::new(FilePathMapping::empty()));
                 let psess = ParseSess::with_dcx(dcx, sm);
 
-                let mut parser = match new_parser_from_source_str(&psess, filename, code) {
+                let mut parser = match new_parser_from_source_str(&psess, filename, code,StripTokens::ShebangAndFrontmatter) {
                     Ok(p) => p,
                     Err(errs) => {
                         errs.into_iter().for_each(Diag::cancel);
diff --git a/src/tools/rustfmt/src/parse/parser.rs b/src/tools/rustfmt/src/parse/parser.rs
diff --git a/tests/ui-fulldeps/auxiliary/parser.rs b/tests/ui-fulldeps/auxiliary/parser.rs
diff --git a/tests/ui-fulldeps/mod_dir_path_canonicalized.rs b/tests/ui-fulldeps/mod_dir_path_canonicalized.rs

Original file line number	Diff line number	Diff line change
`@@ -45,7 +45,7 @@ pub(crate) struct UnmatchedDelim {`
`45`	`45`	`}`
`46`	`46`
`47`	`47`	`/// Which tokens should be stripped before lexing the tokens.`
`48`		`-pub(crate) enum StripTokens {`
	`48`	`+pub enum StripTokens {`
`49`	`49`	`/// Strip both shebang and frontmatter.`
`50`	`50`	`ShebangAndFrontmatter,`
`51`	`51`	`/// Strip the shebang but not frontmatter.`