rustfmt cleanup (#2553)

Closes #2540

* test-one: use prettyplease to format generated code

* contributing: note the prettyplease change, state that it is an optional dependency of bindgen, not bindgen-cli

CONTRIBUTING.md

@@ -104,18 +104,18 @@ There are also some integration tests in the `./bindgen-integration` crate, whic
 generate bindings to some C++ code, and then uses the bindings, asserting that
 values are what we expect them to be, both on the Rust and C++ side.
 
-The generated and expected bindings are run through `rustfmt` before they are
-compared. Make sure you have `rustfmt` up to date:
-
-```
-$ rustup update nightly
-$ rustup component add rustfmt --toolchain nightly
-```
+The generated and expected bindings are formatted with [prettyplease] before they are
+compared. It is a default (but optional) dependency of `bindgen`,
+so be sure to keep that in mind
+(if you built `bindgen` with the `--no-default-features` option of Cargo).
+Note also that `rustfmt` formatting is disabled for the `bindgen-tests/tests/expectations/`
+directory tree, which helps avoid failing ui tests.
 
 Note: running `cargo test` from the root directory of `bindgen`'s repository does not
 automatically test the generated bindings or run the integration tests.
 These steps must be performed manually when needed.
 
+
 ### Testing Bindings Generation
 
 To regenerate bindings from the corpus of test headers in `bindgen-tests/tests/headers` and
@@ -576,3 +576,6 @@ $ git push --tags upstream # To publish the tag
 ### Create a new release on Github
 
 See [Releasing projects on Github](https://docs.github.com/en/repositories/releasing-projects-on-github)
+
+
+[prettyplease]: https://github.com/dtolnay/prettyplease

bindgen-tests/tests/test-one.sh

@@ -45,19 +45,18 @@ TEST_BINDINGS_BINARY=$(mktemp -t bindings.XXXXXX)
 FLAGS="$(grep "// bindgen-flags: " "$TEST" || echo)"
 FLAGS="${FLAGS/\/\/ bindgen\-flags:/}"
 # Prepend the default flags added in test.rs's `create_bindgen_builder`.
-FLAGS="--rustfmt-bindings --with-derive-default --raw-line '' --raw-line '#![allow(dead_code, non_snake_case, non_camel_case_types, non_upper_case_globals)]' --raw-line '' $FLAGS"
+FLAGS="--with-derive-default --raw-line '' --raw-line '#![allow(dead_code, non_snake_case, non_camel_case_types, non_upper_case_globals)]' --raw-line '' $FLAGS"
 
 
 eval ../target/debug/bindgen \
     "\"$TEST\"" \
     --emit-ir \
     --emit-ir-graphviz ir.dot \
     --emit-clang-ast \
+    --formatter prettyplease \
     -o "\"$BINDINGS\"" \
     $FLAGS
 
-rustup run nightly rustfmt "$BINDINGS" || true
-
 dot -Tpng ir.dot -o ir.png
 
 echo
@@ -80,8 +79,6 @@ EXPECTED=${TEST/headers/expectations\/tests}
 EXPECTED=${EXPECTED/.hpp/.rs}
 EXPECTED=${EXPECTED/.h/.rs}
 
-rustup run nightly rustfmt "$EXPECTED" || true
-
 # Don't exit early if there is a diff.
 diff -U8 "$EXPECTED" "$BINDINGS" || true