downgrade icu_casemap to dev-dependency

[sftse]

When we fixed #62 we unfortunately acquired a rather large dependency tree.

With some test shenanigans, we can downgrade icu_casemap to a dev-dependency, so downstream consumers do not have to foot the bill. We can even remove it entirely, since we generate a small table now, but then need to manually add it to dependencies again if we want to regenerate the table for newer Unicode standards.

[sftse]

This takes build time from 6.3s on my machine down to 0.7s.

[sftse]

Given how rare it should be to regenerate the exceptional cases, if ever, given how old the format is, I've removed it entirely from the dependencies.

[jmcnamara]

It should be possible to avoid the once_cell dependency as well by using std::sync::OnceLock. It is stable since Rust v1.70.0.

$ git diff
diff --git a/Cargo.toml b/Cargo.toml
index 75dcc2d..db09613 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -11,7 +11,6 @@ edition = "2018"
 
 [dependencies]
 fnv = "1.0"
-once_cell = "1.21.3"
 uuid = "1"
 
 [dev-dependencies]
diff --git a/src/internal/path.rs b/src/internal/path.rs
index 753a709..bc230a8 100644
--- a/src/internal/path.rs
+++ b/src/internal/path.rs
@@ -2,8 +2,7 @@ use std::cmp::Ordering;
 use std::collections::HashMap;
 use std::io;
 use std::path::{Component, Path, PathBuf};
-
-use once_cell::sync::Lazy;
+use std::sync::OnceLock;
 
 // ========================================================================= //
 
@@ -20,7 +19,6 @@ impl CaseMapper {
 }
 
 const MAX_NAME_LEN: usize = 31;
-static CASE_MAPPER: Lazy<CaseMapper> = Lazy::new(CaseMapper::new);
 
 // ========================================================================= //
 
@@ -28,12 +26,15 @@ static CASE_MAPPER: Lazy<CaseMapper> = Lazy::new(CaseMapper::new);
 /// using simple capitalization and the ability to add exceptions.
 /// Used when two directory entry names need to be compared.
 fn cfb_uppercase_char(c: char) -> char {
+    static CASE_MAPPER: OnceLock<CaseMapper> = OnceLock::new();
+    let case_mapper = CASE_MAPPER.get_or_init(CaseMapper::new);
+
     // TODO: Edge cases can be added that appear
     // in the table from Appendix A, <3> Section 2.6.4
 
     // Base case, just do a simple uppercase
     // equivalent to icu_casemap::CaseMapper::new().simple_uppercase(c)
-    CASE_MAPPER.simple_uppercase(c)
+    case_mapper.simple_uppercase(c)
 }
 
 /// Compares two directory entry names according to CFB ordering, which is
@@ -222,6 +223,8 @@ mod tests {
     #[ignore = "add icu_casemap to dependencies to regenerate exceptional uppercase chars"]
     #[test]
     fn uppercase_generation() {
+        use crate::internal::path::CaseMapper;
+
         struct AsArray(Vec<(char, char)>);
 
         impl std::fmt::Display for AsArray {
@@ -241,7 +244,7 @@ mod tests {
             }
         }
 
-        let case_mapper = &super::CASE_MAPPER;
+        let case_mapper = CaseMapper::new();
         // uncomment line to regenerate exceptions
         // let case_mapper = icu_casemap::CaseMapper::new();

[jmcnamara]

+1 to this PR. It would be great to use rust-cfb in Calamine but the current dependency chain is slightly off-putting.

See also: tafia/calamine#551

[sftse]

I was not explicitly able to determine the current MSRV, so the once_cell is to be a bit more conservative. The uuid dependency states MSRV of 1.63 and once_cell has MSRV 1.65.

If 1.70 is fine we can apply the changes you suggest, thanks.

[jmcnamara]

I was not explicitly able to determine the current MSRV, so the once_cell is to be a bit more conservative. The uuid dependency states MSRV of 1.63 and once_cell has MSRV 1.65.

That is fair.

However the actual MSRV required is higher.

According to cargo-msrv the MSRV on main is v1.81.0 (probably due to the icu-casemap dependencies):

$ cargo-msrv find

...

Result:
   Considered (min … max):   Rust 1.31.1 … Rust 1.89.0
   Search method:            bisect
   MSRV:                     1.81.0
   Target:                   x86_64-apple-darwin

On your branch it goes back a bit further to MSRV v1.74.1:

$ git checkout dependency-reduction


$ cargo-msrv find

...


Result:
   Considered (min … max):   Rust 1.31.1 … Rust 1.89.0
   Search method:            bisect
   MSRV:                     1.74.1
   Target:                   x86_64-apple-darwin

As a manual check I downgraded manually to rustc v1.65.0 and rust-cfb doesn't compile with that version.

It is probably worth specifying the MSRV in Cargo.toml as part of this patchset or in another PR.

[sftse]

Thanks for the investigation and conclusive evidence, the suggestions have been included.

[mdsteele]

Thanks!

[sftse]

Any chance this can be released?

[mdsteele]

Published as v0.12.0.