fix rustdoc `render_call_locations` panicking because of default span `DUMMY_SP` pointing at non local-source file #146091

janis-bhm · 2025-09-01T13:54:15Z

fixes #144752
related to/builds on #145008

bevy still crashes in the same way as #144752 when building docs on nightly, and from what I can tell the cause seems to be the following (copied from zulip #t-rustdoc > docs on nightly with example scrapes crash):

render_call_locations tries to find the source span of a call to add as an example, but the example files are never actually in the source map from what I can tell, and so it falls back to the default span, which points at the first file in the source map.
Now, the issue that guillaume mentions here adds new files to the source map in order to get them into the dep info, and that leads to some files, namely docs-rs/trait-tags.html in the case of bevy because it's added with --html-after-content, being added before any source files, so then the default span points at them, and when href_from_span tries to find the source file corresponding to the span, the file doesn't belong to local_sources, and it short circuits.
This can be fixed by just not using DUMMY_SP as the default span and calculating, for example, the crates root source file as the span, because I'm not entirely sure what the href from that span is actually used for; it's not what links to the example in the end.
I think the proper way of fixing this would be to make sure the example files are part of the local_sources or at least the source map, but I don't know nearly enough about rust internals to be able to figure out how to fix that.

I've included a test that's mostly copied from #145008's test with the addition of --html-after-content after.html in the RUSTDOCFLAGS, which panics on master in conjunction with the -Zrustdoc-scrape-examples cargo flag.

cc @GuillaumeGomez

rustbot · 2025-09-01T13:54:20Z

r? @jieyouxu

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jieyouxu · 2025-09-01T14:02:57Z

r? rustdoc

GuillaumeGomez · 2025-09-01T15:12:54Z

src/librustdoc/html/render/mod.rs

@@ -2829,7 +2829,21 @@ fn render_call_locations<W: fmt::Write>(
                file.start_pos + BytePos(byte_max),
            ))
        })()
-        .unwrap_or(DUMMY_SP);
+        .unwrap_or_else(|| {


Instead of cloning parts of the above code, I think it'd might be simpler to instead tweak it a bit:

let local = tcx.sess.local_crate_source_file()?; let crate_src = local.into_local_path()?; let abs_crate_src = crate_src.canonicalize().ok()?; let crate_root = abs_crate_src.parent()?.parent()?; let rel_path = path.strip_prefix(crate_root).ok()?; let files = source_map.files(); let file = files.iter().find(|file| match &file.name { FileName::Real(RealFileName::LocalPath(other_path)) => rel_path == other_path, _ => false, }).or_else(|| files.iter().find(|file| matches!(&file.name, FileName::Real(file_name) if file_name == &local))?;

Then we can replace the unwrap_or(DUMMY_SP) with expect("no local file found").

rustbot · 2025-09-01T16:33:40Z

Some changes occurred in GUI tests.

cc @GuillaumeGomez

GuillaumeGomez · 2025-09-01T16:51:39Z

tests/rustdoc-gui/src/scrape_examples_ice/src/lib.rs

@@ -0,0 +1,9 @@
+//@ run-flags:-Zrustdoc-scrape-examples
+//@ rustc-env: RUSTDOCFLAGS='--html-after-content after.html'


Please pass --html-after-content after.html directly in run-flags.

GuillaumeGomez · 2025-09-01T16:52:07Z

Also please squash your commits once done.

rustbot · 2025-09-01T20:14:21Z

This PR was rebased onto a different master commit. Here's a range-diff highlighting what actually changed.

Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.

GuillaumeGomez · 2025-09-01T22:03:02Z

tests/rustdoc-gui/search-result-display.goml

@@ -52,7 +52,7 @@ compare-elements-size-near: (
 set-window-size: (900, 900)

 // First we check the current width, height and position.
-assert-css: ("#crate-search", {"width": "159px"})
+assert-css: ("#crate-search", {"width": "185px"})


This change is because the longest crate name increased.

GuillaumeGomez · 2025-09-01T23:00:07Z

Note for myself, once merged, I'll need to add a test for the extra HTML added.

…file outside of local_sources add test against crashing with --html-after-content file correctly add --html-after-content to env not args formatting fix for rustdoc-call-locations-after-content/rmake.rs Use local crate source file as default span in `render_call_locations` - avoids unwrapping the first file added to the source map as a local file in `href_from_span` move test to tests/rustdoc-gui, rename to scrape_examples_ice test link is correct use rustdocflags, rename path in example, track lock file factor out duplicate function calls use compile-flags to make sure the after.html file is actually included in the rustdoc call fix goml go-to path increment assert-count in sidebar-source-code.goml adjust crate-search width in search-result-display.goml renamed Bar in scrape_examples_ice test make crate name shorter ..

GuillaumeGomez · 2025-09-02T08:53:11Z

Thanks for the fix!

@bors r+ rollup

bors · 2025-09-02T08:53:14Z

📌 Commit f67e29e has been approved by GuillaumeGomez

It is now in the queue for this repository.

Rollup of 14 pull requests Successful merges: - #144066 (stabilize c-style varargs for sysv64, win64, efiapi, aapcs) - #145783 (add span to struct pattern rest (..)) - #146034 (Update target spec metadata of Arm64EC Windows and Trusty targets) - #146064 (Add compiler error when trying to use concat metavar expr in repetitions) - #146070 (rustdoc-search: skip loading unneeded fnData) - #146088 (constify impl Try for ControlFlow) - #146089 (fix a constness ordering bug in rustfmt) - #146091 (fix rustdoc `render_call_locations` panicking because of default span `DUMMY_SP` pointing at non local-source file) - #146094 (Make `Parser::parse_for_head` public for rustfmt usage) - #146102 (Remove dead code stemming from an old effects desugaring) - #146115 (Add maintainer for VxWorks) - #146116 (Adjust issue-118306.rs test after LLVM change) - #146117 (Fix search index generation) - #146118 (improve process::abort rendering in Miri backtraces) r? `@ghost` `@rustbot` modify labels: rollup

Rollup merge of #146091 - janis-bhm:rustdoc-default-span-with-simple-test, r=GuillaumeGomez fix rustdoc `render_call_locations` panicking because of default span `DUMMY_SP` pointing at non local-source file fixes #144752 related to/builds on #145008 bevy still crashes in the same way as #144752 when building docs on nightly, and from what I can tell the cause seems to be the following (copied from zulip [#t-rustdoc > docs on nightly with example scrapes crash](https://rust-lang.zulipchat.com/#narrow/channel/266220-t-rustdoc/topic/docs.20on.20nightly.20with.20example.20scrapes.20crash)): > render_call_locations tries to [find](https://github.com/rust-lang/rust/blob/84a17470220e7adf249b18d7c0178dfbede89462/src/librustdoc/html/render/mod.rs#L2816) the source span of a call to add as an example, but the example files are never actually in the source map from what I can tell, and so it falls back to the default span, which points at the first file in the source map. > Now, the issue that guillaume mentions [here](#145008) adds new files to the source map in order to get them into the dep info, and that leads to some files, namely docs-rs/trait-tags.html in the case of bevy because it's added with --html-after-content, being added before any source files, so then the default span points at them, and when href_from_span tries to find the [source file](https://github.com/rust-lang/rust/blob/84a17470220e7adf249b18d7c0178dfbede89462/src/librustdoc/html/render/context.rs#L368) corresponding to the span, the file doesn't belong to local_sources, and it short circuits. > This can be fixed by just not using DUMMY_SP as the default span and calculating, for example, the crates root source file as the span, because I'm not entirely sure what the href from that span is actually used for; it's not what links to the example in the end. > I think the proper way of fixing this would be to make sure the example files are part of the local_sources or at least the source map, but I don't know nearly enough about rust internals to be able to figure out how to fix that. I've included a test that's mostly copied from #145008's test with the addition of `--html-after-content after.html` in the `RUSTDOCFLAGS`, which panics on master in conjunction with the `-Zrustdoc-scrape-examples` cargo flag. cc `@GuillaumeGomez`

Rollup of 14 pull requests Successful merges: - rust-lang/rust#144066 (stabilize c-style varargs for sysv64, win64, efiapi, aapcs) - rust-lang/rust#145783 (add span to struct pattern rest (..)) - rust-lang/rust#146034 (Update target spec metadata of Arm64EC Windows and Trusty targets) - rust-lang/rust#146064 (Add compiler error when trying to use concat metavar expr in repetitions) - rust-lang/rust#146070 (rustdoc-search: skip loading unneeded fnData) - rust-lang/rust#146088 (constify impl Try for ControlFlow) - rust-lang/rust#146089 (fix a constness ordering bug in rustfmt) - rust-lang/rust#146091 (fix rustdoc `render_call_locations` panicking because of default span `DUMMY_SP` pointing at non local-source file) - rust-lang/rust#146094 (Make `Parser::parse_for_head` public for rustfmt usage) - rust-lang/rust#146102 (Remove dead code stemming from an old effects desugaring) - rust-lang/rust#146115 (Add maintainer for VxWorks) - rust-lang/rust#146116 (Adjust issue-118306.rs test after LLVM change) - rust-lang/rust#146117 (Fix search index generation) - rust-lang/rust#146118 (improve process::abort rendering in Miri backtraces) r? `@ghost` `@rustbot` modify labels: rollup

…d-examples, r=lolbinarycat [rustdoc] Uncomment code to add scraped rustdoc examples in loaded paths Since the bug was fixed in rust-lang#146091, we can now uncomment the code. :) r? lolbinarycat

Rollup merge of #146161 - GuillaumeGomez:loaded-paths-scraped-examples, r=lolbinarycat [rustdoc] Uncomment code to add scraped rustdoc examples in loaded paths Since the bug was fixed in #146091, we can now uncomment the code. :) r? lolbinarycat

…s, r=lolbinarycat [rustdoc] Uncomment code to add scraped rustdoc examples in loaded paths Since the bug was fixed in rust-lang/rust#146091, we can now uncomment the code. :) r? lolbinarycat

… r=lolbinarycat Ensure that `--html-after-content` option is used to check `scrape_examples_ice` rustdoc GUI test Follow-up of rust-lang#146091. This test ensures that the spans are correctly handled when a "local source file" is not the first in the file list. To ensure it's actually what's tested, this test checks that the option is actually used by adding an element. r? `@lolbinarycat`

Rollup merge of #146242 - GuillaumeGomez:rustdoc-gui-scrape, r=lolbinarycat Ensure that `--html-after-content` option is used to check `scrape_examples_ice` rustdoc GUI test Follow-up of #146091. This test ensures that the spans are correctly handled when a "local source file" is not the first in the file list. To ensure it's actually what's tested, this test checks that the option is actually used by adding an element. r? `@lolbinarycat`

rustbot assigned jieyouxu Sep 1, 2025

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janis-bhm force-pushed the rustdoc-default-span-with-simple-test branch from a177355 to 6a3975e Compare September 1, 2025 20:14

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janis-bhm force-pushed the rustdoc-default-span-with-simple-test branch from 6c8d64e to 65567a7 Compare September 1, 2025 22:01

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janis-bhm force-pushed the rustdoc-default-span-with-simple-test branch from 65567a7 to f67e29e Compare September 1, 2025 23:42

bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Sep 2, 2025

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Rollup of 14 pull requests #146125

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bors merged commit 15cde9c into rust-lang:master Sep 2, 2025
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rustbot added this to the 1.91.0 milestone Sep 2, 2025

alice-i-cecile mentioned this pull request Sep 2, 2025

building docs is failing bevyengine/bevy#20386

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GuillaumeGomez mentioned this pull request Sep 3, 2025

[rustdoc] Uncomment code to add scraped rustdoc examples in loaded paths #146161

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Ensure that --html-after-content option is used to check scrape_examples_ice rustdoc GUI test #146242

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fix rustdoc `render_call_locations` panicking because of default span `DUMMY_SP` pointing at non local-source file #146091

fix rustdoc `render_call_locations` panicking because of default span `DUMMY_SP` pointing at non local-source file #146091

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		@@ -0,0 +1,9 @@
		//@ run-flags:-Zrustdoc-scrape-examples
		//@ rustc-env: RUSTDOCFLAGS='--html-after-content after.html'

fix rustdoc render_call_locations panicking because of default span DUMMY_SP pointing at non local-source file #146091

fix rustdoc render_call_locations panicking because of default span DUMMY_SP pointing at non local-source file #146091

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fix rustdoc `render_call_locations` panicking because of default span `DUMMY_SP` pointing at non local-source file #146091

fix rustdoc `render_call_locations` panicking because of default span `DUMMY_SP` pointing at non local-source file #146091

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