Add pretty_format_json as builtin hook

Cargo.toml

@@ -85,6 +85,7 @@ serde_stacker = { version = "0.1.12" }
 serde-saphyr = { version = "0.0.21", default-features = false }
 shlex = { version = "1.3.0" }
 globset = { version = "0.4.18" }
+similar = { version = "2.7.0" }
 strum = { version = "0.28.0", features = ["derive"] }
 target-lexicon = { version = "0.13.0" }
 tempfile = { version = "3.25.0" }

crates/prek/Cargo.toml

@@ -73,6 +73,7 @@ serde_json = { workspace = true }
 serde_stacker = { workspace = true }
 serde-saphyr = { workspace = true }
 shlex = { workspace = true }
+similar = { workspace = true }
 strum = { workspace = true }
 target-lexicon = { workspace = true }
 tempfile = { workspace = true }

crates/prek/src/hooks/builtin_hooks/mod.rs

@@ -48,6 +48,7 @@ pub(crate) enum BuiltinHooks {
     FixByteOrderMarker,
     MixedLineEnding,
     NoCommitToBranch,
+    PrettyFormatJson,
     TrailingWhitespace,
 }
 
@@ -97,6 +98,7 @@ impl BuiltinHooks {
             }
             Self::MixedLineEnding => pre_commit_hooks::mixed_line_ending(hook, filenames).await,
             Self::NoCommitToBranch => pre_commit_hooks::no_commit_to_branch(hook).await,
+            Self::PrettyFormatJson => pre_commit_hooks::pretty_format_json(hook, filenames).await,
             Self::TrailingWhitespace => {
                 pre_commit_hooks::fix_trailing_whitespace(hook, filenames).await
             }
@@ -362,6 +364,18 @@ impl BuiltinHook {
                     ..Default::default()
                 },
             },
+            BuiltinHooks::PrettyFormatJson => BuiltinHook {
+                id: "pretty-format-json".to_string(),
+                name: "pretty format json".to_string(),
+                entry: "pretty-format-json".to_string(),
+                priority: None,
+                options: HookOptions {
+                    description: Some("checks that JSON files are pretty-formatted.".to_string()),
+                    types: Some(tags::TAG_SET_JSON),
+                    stages: Some([Stage::PreCommit, Stage::PrePush, Stage::Manual].into()),
+                    ..Default::default()
+                },
+            },
             BuiltinHooks::TrailingWhitespace => BuiltinHook {
                 id: "trailing-whitespace".to_string(),
                 name: "trim trailing whitespace".to_string(),

crates/prek/src/hooks/pre_commit_hooks/mod.rs

@@ -24,6 +24,7 @@ mod fix_end_of_file;
 mod fix_trailing_whitespace;
 mod mixed_line_ending;
 mod no_commit_to_branch;
+mod pretty_format_json;
 mod shebangs;
 
 pub(crate) use check_added_large_files::check_added_large_files;
@@ -45,6 +46,7 @@ pub(crate) use fix_end_of_file::fix_end_of_file;
 pub(crate) use fix_trailing_whitespace::fix_trailing_whitespace;
 pub(crate) use mixed_line_ending::mixed_line_ending;
 pub(crate) use no_commit_to_branch::no_commit_to_branch;
+pub(crate) use pretty_format_json::pretty_format_json;
 
 /// Hooks from `https://github.com/pre-commit/pre-commit-hooks`.
 #[derive(strum::EnumString)]
@@ -68,6 +70,10 @@ pub(crate) enum PreCommitHooks {
     MixedLineEnding,
     DetectPrivateKey,
     NoCommitToBranch,
+    // `pretty-format-json` is intentionally builtin-only for now. Do not enable
+    // automatic fast-path replacement until parity coverage against upstream
+    // Python is broad enough to trust it as the default implementation.
+    // PrettyFormatJson,
     TrailingWhitespace,
 }