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Stabilize ties in preproc order through name sort

This commit is contained in:
ISSOtm 2021-09-26 21:54:14 +02:00
parent 9c34e602bd
commit 6b784be616
2 changed files with 35 additions and 20 deletions
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10
guide/src/format/configuration/preprocessors.md
View File

@ -59,8 +59,8 @@ command = "python random.py"
### Require A Certain Order
The order in which preprocessors are run is not guaranteed, but you can request some to run before or after others.
For example, suppose you want your `linenos` preprocessor to process lines that may have been `{{#include}}`d; then you want it to run after the built-in `links` preprocessor, which you can require using the `before` and/or `after` fields.
The order in which preprocessors are run can be controlled with the `before` and `after` fields.
For example, suppose you want your `linenos` preprocessor to process lines that may have been `{{#include}}`d; then you want it to run after the built-in `links` preprocessor, which you can require using either the `before` or `after` field:
```toml
[preprocessor.linenos]
@ -74,7 +74,7 @@ or
before = [ "linenos" ]
```
It would be possible, though redundant, to specify both of the above in the same config file.
It would also be possible, though redundant, to specify both of the above in the same config file.
`mdbook` will detect any infinite loops and error out.
Note that order of preprocessors besides what is specified using `before` and `after` is not guaranteed, and may change within the same run of `mdbook`.
Preprocessors having the same priority specified through `before` and `after` are sorted by name.
Any infinite loops will be detected and produce an error.

45
src/book/mod.rs
View File

@ -435,21 +435,36 @@ fn determine_preprocessors(config: &Config) -> Result<Vec<Box<dyn Preprocessor>>
// Now that all links have been established, queue preprocessors in a suitable order
let mut preprocessors = Vec::with_capacity(preprocessor_names.len());
while let Some(name) = preprocessor_names.pop() {
let preprocessor: Box<dyn Preprocessor> = match name.as_str() {
"links" => Box::new(LinkPreprocessor::new()),
"index" => Box::new(IndexPreprocessor::new()),
_ => {
// The only way to request a custom preprocessor is through the `preprocessor`
// table, so it must exist, be a table, and contain the key.
let table = &config.get("preprocessor").unwrap().as_table().unwrap()[&name];
let command = get_custom_preprocessor_cmd(&name, table);
Box::new(CmdPreprocessor::new(name, command))
}
};
preprocessors.push(preprocessor);
// `pop_all()` returns an empty vector when no more items are not being depended upon
for mut names in std::iter::repeat_with(|| preprocessor_names.pop_all())
.take_while(|names| !names.is_empty())
{
// The `topological_sort` crate does not guarantee a stable order for ties, even across
// runs of the same program. Thus, we break ties manually by sorting.
// Careful: `str`'s default sorting, which we are implicitly invoking here, uses code point
// values ([1]), which may not be an alphabetical sort.
// As mentioned in [1], doing so depends on locale, which is not desirable for deciding
// preprocessor execution order.
// [1]: https://doc.rust-lang.org/stable/std/cmp/trait.Ord.html#impl-Ord-14
names.sort();
for name in names {
let preprocessor: Box<dyn Preprocessor> = match name.as_str() {
"links" => Box::new(LinkPreprocessor::new()),
"index" => Box::new(IndexPreprocessor::new()),
_ => {
// The only way to request a custom preprocessor is through the `preprocessor`
// table, so it must exist, be a table, and contain the key.
let table = &config.get("preprocessor").unwrap().as_table().unwrap()[&name];
let command = get_custom_preprocessor_cmd(&name, table);
Box::new(CmdPreprocessor::new(name, command))
}
};
preprocessors.push(preprocessor);
}
}
// "If `pop_all` returns an empty vector and `len` is not 0, there are cyclic dependencies."
// Normally, `len() == 0` is equivalent to `is_empty()`, so we'll use that.
if preprocessor_names.is_empty() {
Ok(preprocessors)
} else {
@ -562,8 +577,8 @@ mod tests {
assert!(got.is_ok());
assert_eq!(got.as_ref().unwrap().len(), 2);
assert_eq!(got.as_ref().unwrap()[0].name(), "links");
assert_eq!(got.as_ref().unwrap()[1].name(), "index");
assert_eq!(got.as_ref().unwrap()[0].name(), "index");
assert_eq!(got.as_ref().unwrap()[1].name(), "links");
}
#[test]