rustdoc: make doctest span tweak a 2024 edition change

Fixes rust-lang#132203

This is a compatibility hack, because I think the new behavior is better.
When an A `include_str!` B, and B `include_str!` C, the path to C should
be resolved relative to B, not A. That's how `include!` itself works,
so that's how `include_str!` with should work.

src/librustdoc/doctest/rust.rs

@@ -113,7 +113,19 @@ impl<'tcx> HirCollector<'tcx> {
         let attrs = Attributes::from_ast(ast_attrs);
         if let Some(doc) = attrs.opt_doc_value() {
             let span = span_of_fragments(&attrs.doc_strings).unwrap_or(sp);
-            self.collector.position = span;
+            self.collector.position = if span.edition().at_least_rust_2024() {
+                span
+            } else {
+                // this span affects filesystem path resolution,
+                // so we need to keep it the same as it was previously
+                ast_attrs
+                    .iter()
+                    .find(|attr| attr.doc_str().is_some())
+                    .map(|attr| {
+                        attr.span.ctxt().outer_expn().expansion_cause().unwrap_or(attr.span)
+                    })
+                    .unwrap_or(DUMMY_SP)
+            };
             markdown::find_testable_code(
                 &doc,
                 &mut self.collector,

tests/rustdoc-ui/doctest/auxiliary/extern_macros_2024.rs

@@ -0,0 +1,10 @@
+//@ edition:2024
+//@ compile-flags:-Z unstable-options
+#![crate_name="extern_macros"]
+#[macro_export]
+macro_rules! attrs_on_struct {
+    ( $( #[$attr:meta] )* ) => {
+        $( #[$attr] )*
+        pub struct ExpandedStruct;
+    }
+}

tests/rustdoc-ui/doctest/auxiliary/relative-dir.md

@@ -0,0 +1,3 @@
+```rust
+let x = include_bytes!("relative-dir-empty-file");
+```

tests/rustdoc-ui/doctest/doctest-output-include-fail.rs

@@ -1,4 +1,5 @@
-//@ compile-flags:--test --test-args=--test-threads=1
+//@ edition:2024
+//@ compile-flags:--test --test-args=--test-threads=1 -Z unstable-options
 //@ normalize-stdout-test: "tests/rustdoc-ui/doctest" -> "$$DIR"
 //@ normalize-stdout-test: "finished in \d+\.\d+s" -> "finished in $$TIME"
 //@ failure-status: 101

tests/rustdoc-ui/doctest/doctest-output.edition2015.stdout

@@ -0,0 +1,8 @@
+
+running 3 tests
+test $DIR/doctest-output.rs - (line 12) ... ok
+test $DIR/doctest-output.rs - ExpandedStruct (line 28) ... ok
+test $DIR/doctest-output.rs - foo::bar (line 22) ... ok
+
+test result: ok. 3 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in $TIME
+

tests/rustdoc-ui/doctest/doctest-output.edition2024.stdout

@@ -0,0 +1,8 @@
+
+running 3 tests
+test $DIR/doctest-output.rs - (line 12) ... ok
+test $DIR/doctest-output.rs - ExpandedStruct (line 28) ... ok
+test $DIR/doctest-output.rs - foo::bar (line 22) ... ok
+
+test result: ok. 3 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in $TIME
+

tests/rustdoc-ui/doctest/doctest-output.rs

@@ -1,6 +1,10 @@
-//@ edition:2018
-//@ aux-build:extern_macros.rs
-//@ compile-flags:--test --test-args=--test-threads=1
+//@ revisions: edition2015 edition2024
+//@[edition2015]edition:2015
+//@[edition2015]aux-build:extern_macros.rs
+//@[edition2015]compile-flags:--test --test-args=--test-threads=1
+//@[edition2024]edition:2015
+//@[edition2024]aux-build:extern_macros.rs
+//@[edition2024]compile-flags:--test --test-args=--test-threads=1 -Z unstable-options
 //@ normalize-stdout-test: "tests/rustdoc-ui/doctest" -> "$$DIR"
 //@ normalize-stdout-test: "finished in \d+\.\d+s" -> "finished in $$TIME"
 //@ check-pass

tests/rustdoc-ui/doctest/relative-path-include-bytes-132203.edition2015.stdout

@@ -0,0 +1,24 @@
+
+running 1 test
+test $DIR/relative-path-include-bytes-132203.rs - (line 17) ... FAILED
+
+failures:
+
+---- $DIR/relative-path-include-bytes-132203.rs - (line 17) stdout ----
+error: couldn't read `$DIR/relative-dir-empty-file`: No such file or directory (os error 2)
+  --> $DIR/relative-path-include-bytes-132203.rs:18:9
+   |
+LL | let x = include_bytes!("relative-dir-empty-file");
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: this error originates in the macro `include_bytes` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: aborting due to 1 previous error
+
+Couldn't compile the test.
+
+failures:
+    $DIR/relative-path-include-bytes-132203.rs - (line 17)
+
+test result: FAILED. 0 passed; 1 failed; 0 ignored; 0 measured; 0 filtered out; finished in $TIME
+

tests/rustdoc-ui/doctest/relative-path-include-bytes-132203.edition2024.stdout

@@ -0,0 +1,6 @@
+
+running 1 test
+test $DIR/auxiliary/relative-dir.md - (line 1) ... ok
+
+test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in $TIME
+

tests/rustdoc-ui/doctest/relative-path-include-bytes-132203.rs

@@ -0,0 +1,17 @@
+//@ revisions: edition2015 edition2024
+//@[edition2015]edition:2015
+//@[edition2015]check-fail
+//@[edition2015]failure-status: 101
+//@[edition2015]compile-flags:--test --test-args=--test-threads=1
+//@[edition2024]edition:2024
+//@[edition2024]check-pass
+//@[edition2024]compile-flags:--test --test-args=--test-threads=1 -Z unstable-options
+//@ normalize-stdout-test: "tests/rustdoc-ui/doctest" -> "$$DIR"
+//@ normalize-stdout-test: "finished in \d+\.\d+s" -> "finished in $$TIME"
+
+// https://github.com/rust-lang/rust/issues/132203
+// This version, because it's edition2024, passes thanks to the new
+// relative path. The edition2015 version fails, because paths are
+// resolved relative to the rs file instead of relative to the md file.
+
+#![doc=include_str!("auxiliary/relative-dir.md")]