loco-rs/loco · error

found no ```rust blocks in

Error message

found no ```rust blocks in {RUST_DIRS:?} — the extractor is broken, not the docs

What it means

Companion check to the docs check: after collecting ```rust blocks from the docs tree, the tool scans the source directories listed in `RUST_DIRS` and bails if it found no *new* blocks there. This catches the extractor silently failing on source trees, again blamed on the extractor rather than the code.

Solutions

1. Verify the `RUST_DIRS` constant lists existing directories relative to the project root
2. Test the fence-matching logic in `collect` against a known doc-commented file
3. Restore or fix the source directories referenced by `RUST_DIRS`

Example fix

// before
const RUST_DIRS: &[&str] = &["crates/loco-rs/src"];
// after
const RUST_DIRS: &[&str] = &["src", "loco-gen/src", "loco-new/src"];

assert!(RUST_DIRS.iter().all(|d| Path::new(d).is_dir()), "RUST_DIRS entries missing");

When it happens

Trigger: Running the checker when none of the files in `RUST_DIRS` yield ```rust blocks — e.g. a misconfigured `RUST_DIRS` constant, renamed source directories, or a broken fence parser.

Common situations: After renaming src directories without updating `RUST_DIRS`; after refactoring `collect()`; running against a checkout where source files were stripped.

Understand the failure class

Background: EmptyResultError / "no results found": when an API or scraper succeeds but returns zero rows — this error's family across 9 libraries.

Related errors

• found no ```rust blocks under
• : : ` ` needs a reason — write it as ```rust ="why this is…
• does not exist
• : : ```rust block is never closed

AI-assisted analysis of loco-rs/loco@23639d1e36 (2026-09-12). Data as JSON: /api/errors/7b88ffe2676396dd. Report an issue: GitHub.

Appendix: source

Thrown at xtask/src/docs_syntax.rs:76

    if !root.is_dir() {
        bail!("{} does not exist", root.display());
    }

    let mut blocks = Vec::new();
    collect(&root, &mut blocks)?;
    if blocks.is_empty() {
        bail!(
            "found no ```rust blocks under {} — the extractor is broken, not the docs",
            root.display()
        );
    }

    let before_sources = blocks.len();
    for dir in RUST_DIRS {
        collect(&project_dir.join(dir), &mut blocks)?;
    }
    if blocks.len() == before_sources {
        bail!("found no ```rust blocks in {RUST_DIRS:?} — the extractor is broken, not the docs");
    }

    let mut failures = Vec::new();
    let mut checked = 0;
    let mut skipped = 0;

    for block in &blocks {
        if block.skipped {
            skipped += 1;
            continue;
        }
        checked += 1;
        if let Err(error) = parse(&block.code) {
            failures.push(format!(
                "{}:{}: not valid Rust — {error}\n    (if this is deliberate, write the fence as ```rust {SKIP_MARKER}=\"why\")",
                block.file.display(),
                block.line,
            ));

View on GitHub (pinned to 23639d1e36)