Add cargo feature for enabling gettext extraction

This allows having the proc macro crate as an optional dependency and speeds up
compilation in situations where `FISH_GETTEXT_EXTRACTION_FILE` changes, such as
the `build_tools/check.sh` script. Because we don't need to recompile on changes
to the environment variable when the feature is disabled, cargo can reuse
earlier compilation results instead of recompiling everything.
This speeds up the compilation work in `build_tools/check.sh` when no changes
were made which necessitate recompilation.
For such runs of `build_tools/check.sh`, these changes reduce the runtime on my
system by about 10 seconds, from 70 to 60, approximately.
The difference comes from the following two commands recompiling code without
the changes in this commit, but not with them:
- `cargo test --doc --workspace`
- `cargo doc --workspace`

Cargo.toml

@@ -49,7 +49,7 @@ nix = { version = "0.30.1", default-features = false, features = [
 num-traits = "0.2.19"
 once_cell = "1.19.0"
 fish-printf = { path = "./printf", features = ["widestring"] }
-fish-gettext-extraction = { path = "./gettext-extraction" }
+fish-gettext-extraction = { path = "./gettext-extraction", optional = true }
 
 # Don't use the "getrandom" feature as it requires "getentropy" which was not
 # available on macOS < 10.12. We can enable "getrandom" when we raise the
@@ -95,6 +95,11 @@ path = "src/bin/fish_key_reader.rs"
 default = ["embed-data"]
 benchmark = []
 embed-data = ["dep:rust-embed"]
+# This feature is used to enable extracting messages from the source code for localization.
+# It only needs to be enabled if updating these messages (and the corresponding PO files) is
+# desired. This happens when running tests via `build_tools/check.sh` and when calling
+# `build_tools/update_translations.fish`, so there should not be a need to enable it manually.
+gettext-extract = ["dep:fish-gettext-extraction"]
 
 # The following features are auto-detected by the build-script and should not be enabled manually.
 asan = []

build.rs

@@ -82,6 +82,7 @@ fn main() {
     #[cfg(not(clippy))]
     rsconf::rebuild_if_paths_changed(&SPHINX_DOC_SOURCES);
 
+    #[cfg(feature = "gettext-extract")]
     rsconf::rebuild_if_env_changed("FISH_GETTEXT_EXTRACTION_FILE");
 
     cc::Build::new().file("src/libc.c").compile("flibc.a");

build_tools/check.sh

@@ -38,7 +38,7 @@ repo_root="$(dirname "$0")/.."
 build_dir="${CARGO_TARGET_DIR:-$repo_root/target}/${target_triple}/debug"
 
 template_file=$(mktemp)
-FISH_GETTEXT_EXTRACTION_FILE=$template_file cargo build --workspace --all-targets
+FISH_GETTEXT_EXTRACTION_FILE=$template_file cargo build --workspace --all-targets --features=gettext-extract
 if $lint; then
     PATH="$build_dir:$PATH" "$repo_root/build_tools/style.fish" --all --check
     cargo clippy --workspace --all-targets

build_tools/fish_xgettext.fish

@@ -27,7 +27,7 @@ begin
     else
         set rust_extraction_file (mktemp)
         # We need to build to ensure that the proc macro for extracting strings runs.
-        FISH_GETTEXT_EXTRACTION_FILE=$rust_extraction_file cargo check
+        FISH_GETTEXT_EXTRACTION_FILE=$rust_extraction_file cargo check --features=gettext-extract
         or exit 1
     end
 

build_tools/update_translations.fish

@@ -29,7 +29,7 @@
 # `FILE` must be the path to a gettext template file generated from our compilation process.
 # It can be obtained by running:
 #   set -l FILE (mktemp)
-#   FISH_GETTEXT_EXTRACTION_FILE=$FILE cargo check
+#   FISH_GETTEXT_EXTRACTION_FILE=$FILE cargo check --features=gettext-extract
 
 # The sort utility is locale-sensitive.
 # Ensure that sorting output is consistent by setting LC_ALL here.

src/lib.rs

@@ -107,6 +107,7 @@
 pub mod widecharwidth;
 pub mod wildcard;
 
+#[cfg(feature = "gettext-extract")]
 pub extern crate fish_gettext_extraction;
 
 #[cfg(test)]

src/wutil/gettext.rs

@@ -173,6 +173,7 @@ fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
 /// The essential part is the invocation of the proc macro,
 /// which ensures that the string gets extracted for localization.
 #[macro_export]
+#[cfg(feature = "gettext-extract")]
 macro_rules! localizable_string {
     ($string:literal) => {
         $crate::wutil::gettext::LocalizableString::Static(widestring::utf32str!(
@@ -180,6 +181,13 @@ macro_rules! localizable_string {
         ))
     };
 }
+#[macro_export]
+#[cfg(not(feature = "gettext-extract"))]
+macro_rules! localizable_string {
+    ($string:literal) => {
+        $crate::wutil::gettext::LocalizableString::Static(widestring::utf32str!($string))
+    };
+}
 pub use localizable_string;
 
 /// Macro for declaring string consts which should be localized.