Error: The "spec" preprocessor exited unsuccessfully with exit status: 1 status #2130
Description
I tried building the book locally, but received the following error:
aliceryhl@aliceryhl:~/reference$ rm -rf mdbook-spec book target
aliceryhl@aliceryhl:~/reference$ git status
On branch master
Your branch is up to date with 'upstream/master'.
nothing to commit, working tree clean
aliceryhl@aliceryhl:~/reference$ SPEC_RELATIVE=0 mdbook build
2026-01-08 09:00:37 [INFO] (mdbook::book): Book building has started
Compiling proc-macro2 v1.0.103
Compiling quote v1.0.42
Compiling unicode-ident v1.0.22
Compiling memchr v2.7.6
Compiling serde_core v1.0.228
Compiling once_cell v1.21.3
Compiling regex-syntax v0.8.8
Compiling serde_json v1.0.145
Compiling anyhow v1.0.100
Compiling bitflags v2.10.0
Compiling libc v0.2.178
Compiling winnow v0.7.14
Compiling pin-project-lite v0.2.16
Compiling serde v1.0.228
Compiling ryu v1.0.20
Compiling getrandom v0.3.4
Compiling toml_writer v1.0.4
Compiling itoa v1.0.15
Compiling pulldown-cmark v0.13.0
Compiling rustix v1.1.2
Compiling cfg-if v1.0.4
Compiling linux-raw-sys v0.11.0
Compiling unicase v2.8.1
Compiling same-file v1.0.6
Compiling pulldown-cmark-escape v0.11.0
Compiling diagnostics v0.0.0 (/usr/local/google/home/aliceryhl/reference/tools/diagnostics)
Compiling fastrand v2.3.0
Compiling unicode-width v0.2.2
Compiling pathdiff v0.2.3
Compiling semver v1.0.27
Compiling walkdir v2.5.0
Compiling tracing-core v0.1.35
Compiling railroad v0.3.3
Compiling aho-corasick v1.1.4
Compiling syn v2.0.111
Compiling toml_parser v1.0.4
Compiling regex-automata v0.4.13
Compiling tempfile v3.23.0
Compiling serde_spanned v1.0.3
Compiling toml_datetime v0.7.3
Compiling toml v0.9.8
Compiling tracing-attributes v0.1.31
Compiling serde_derive v1.0.228
Compiling regex v1.12.2
Compiling grammar v0.0.0 (/usr/local/google/home/aliceryhl/reference/tools/grammar)
Compiling tracing v0.1.43
Compiling mdbook-markdown v0.5.2
Compiling mdbook-core v0.5.2
Compiling mdbook-preprocessor v0.5.2
Compiling mdbook-spec v0.0.0 (/usr/local/google/home/aliceryhl/reference/tools/mdbook-spec)
Finished `release` profile [optimized] target(s) in 11.37s
Running `target/release/mdbook-spec supports html`
Finished `release` profile [optimized] target(s) in 0.07s
Running `target/release/mdbook-spec`
Unable to parse the input
2026-01-08 09:00:49 [ERROR] (mdbook::utils): Error: The "spec" preprocessor exited unsuccessfully with exit status: 1 status