Add rustfmt to the update-rustc script

With a mechanism to ignore particular listings for various reasons

ADMIN_TASKS.md

@@ -68,6 +68,10 @@ listing beyond the most trivial should be extracted into a file. To do that:
   of user input or external events like making a web request), keep the output inline but make a
   comment that contains `manual-regeneration` and instructions for manually updating the inline
   output.
+- If you don't want this example to even be attempted to be formatted by `rustfmt` (for example
+  because the example doesn't parse on purpose), add a `rustfmt-ignore` file in the listing's
+  directory and the reason it's not being formatted as the contents of that file (in case it's a
+  rustfmt bug that might get fixed someday).
 
 ## See the effect of some change on the rendered book
 

listings/ch03-common-programming-concepts/no-listing-19-statements-vs-expressions/rustfmt-ignore

@@ -0,0 +1 @@
+This listing deliberately doesn't parse so rustfmt fails.

listings/ch04-understanding-ownership/listing-04-01/rustfmt-ignore

@@ -0,0 +1,3 @@
+We have some weird comments pointing out borrowing scopes that we don't want to change;
+unfortunately I haven't found a way to skip them with rustfmt that works so for now we're going to
+manually skip those listings. See: https://github.com/rust-lang/rustfmt/issues/4028

listings/ch04-understanding-ownership/listing-04-03/rustfmt-ignore

@@ -0,0 +1,3 @@
+We have some weird comments pointing out borrowing scopes that we don't want to change;
+unfortunately I haven't found a way to skip them with rustfmt that works so for now we're going to
+manually skip those listings. See: https://github.com/rust-lang/rustfmt/issues/4028

listings/ch04-understanding-ownership/listing-04-04/rustfmt-ignore

@@ -0,0 +1,3 @@
+We have some weird comments pointing out borrowing scopes that we don't want to change;
+unfortunately I haven't found a way to skip them with rustfmt that works so for now we're going to
+manually skip those listings. See: https://github.com/rust-lang/rustfmt/issues/4028

listings/ch04-understanding-ownership/no-listing-02-string-scope/rustfmt-ignore

@@ -0,0 +1,3 @@
+We have some weird comments pointing out borrowing scopes that we don't want to change;
+unfortunately I haven't found a way to skip them with rustfmt that works so for now we're going to
+manually skip those listings. See: https://github.com/rust-lang/rustfmt/issues/4028

listings/ch04-understanding-ownership/no-listing-08-reference-with-annotations/rustfmt-ignore

@@ -0,0 +1,3 @@
+We have some weird comments pointing out borrowing scopes that we don't want to change;
+unfortunately I haven't found a way to skip them with rustfmt that works so for now we're going to
+manually skip those listings. See: https://github.com/rust-lang/rustfmt/issues/4028

listings/ch04-understanding-ownership/no-listing-15-dangling-reference-annotated/rustfmt-ignore

@@ -0,0 +1,3 @@
+We have some weird comments pointing out borrowing scopes that we don't want to change;
+unfortunately I haven't found a way to skip them with rustfmt that works so for now we're going to
+manually skip those listings. See: https://github.com/rust-lang/rustfmt/issues/4028

listings/ch10-generic-types-traits-and-lifetimes/listing-10-18/rustfmt-ignore

@@ -0,0 +1,3 @@
+We have some weird comments pointing out borrowing scopes that we don't want to change;
+unfortunately I haven't found a way to skip them with rustfmt that works so for now we're going to
+manually skip those listings. See: https://github.com/rust-lang/rustfmt/issues/4028

listings/ch10-generic-types-traits-and-lifetimes/listing-10-19/rustfmt-ignore

@@ -0,0 +1,3 @@
+We have some weird comments pointing out borrowing scopes that we don't want to change;
+unfortunately I haven't found a way to skip them with rustfmt that works so for now we're going to
+manually skip those listings. See: https://github.com/rust-lang/rustfmt/issues/4028

listings/ch14-more-about-cargo/output-only-01-adder-crate/add/rustfmt-ignore

@@ -0,0 +1,2 @@
+This listing is used for demonstrating how to set up a workspace, but the workspace isn't
+completely set up yet, so rustfmt complains the crate mentioned in Cargo.toml doesn't exist yet.

listings/ch18-patterns-and-matching/listing-18-25/rustfmt-ignore

@@ -0,0 +1 @@
+This listing deliberately doesn't parse so rustfmt fails.

rustfmt.toml

@@ -0,0 +1 @@
+max_width = 80

tools/src/bin/release_listings.rs

@@ -67,6 +67,7 @@ fn main() -> Result<(), Box<dyn Error>> {
 //
 // - `target` directories
 // - `output.txt` files used to display output in the book
+// - `rustfmt-ignore` files used to signal to update-rustc.sh the listing shouldn't be formatted
 // - anchor comments or snip comments
 // - empty `main` functions in `lib.rs` files used to trick rustdoc
 fn copy_cleaned_listing_files(from: PathBuf, to: PathBuf) -> Result<(), Box<dyn Error>> {
@@ -84,8 +85,8 @@ fn copy_cleaned_listing_files(from: PathBuf, to: PathBuf) -> Result<(), Box<dyn
                 copy_cleaned_listing_files(item_path, output_item)?;
             }
         } else {
-            // Don't copy output files
-            if item_name != "output.txt" {
+            // Don't copy output files or files that tell update-rustc.sh not to format
+            if item_name != "output.txt" && item_name != "rustfmt-ignore" {
                 let item_extension = item_path.extension();
                 if item_extension.is_some() && item_extension.unwrap() == "rs" {
                     copy_cleaned_rust_file(item_name, &item_path, &output_item)?;

tools/update-rustc.sh

@@ -6,7 +6,19 @@ set -eu
 echo 'Building book into `tmp/book-before` before updating...'
 mdbook build -d tmp/book-before
 
-# TODO: Rustfmt all listings here
+# Rustfmt all listings
+echo 'Formatting all listings...'
+find -s listings -name Cargo.toml -print0 | while IFS= read -r -d '' f; do
+    dir_to_fmt=$(dirname $f)
+
+    # There are a handful of listings we don't want to rustfmt and skipping doesn't work;
+    # those will have a file in their directory that explains why.
+    if [ ! -f "${dir_to_fmt}/rustfmt-ignore" ]; then
+        cd $dir_to_fmt
+        cargo fmt --all && true
+        cd - > /dev/null
+    fi
+done
 
 # Get listings without anchor comments in tmp by compiling a release listings artifact
 echo 'Generate listings without anchor comments...'