fix(formatter_json): preserve key and literal value for json-stringify (#23996)

Part of #23923

Do not transform object key, string and number values with `json-stringify`.

crates/oxc_formatter_json/src/print/mod.rs

@@ -44,6 +44,10 @@ pub fn write_quoted_str<'a>(f: &mut JsonFormatter<'_, 'a>, quote_byte: u8, body:
 /// JS stringifies the parsed value into a different shape (`"16"` for `0x10`, `"NaN"` for `1_2`),
 /// Rust simply fails to parse, so `Err` mapping to `false` matches.
 pub fn number_string_round_trips(s: &str) -> bool {
+    // PERF: Use `dragonbox_ecma` directly instead of `oxc_syntax::ToJsString`
+    // The latter returns `String` (heap alloc),
+    // while `Buffer::format` returns `&str` borrowed from a stack buffer.
+    // This is only a `==` comparison on a hot path (every numeric key), so avoid the alloc.
     s.parse::<f64>()
         .is_ok_and(|value| value.is_finite() && dragonbox_ecma::Buffer::new().format(value) == s)
 }

crates/oxc_formatter_json/src/print/stringify.rs

@@ -25,10 +25,6 @@ use super::{
     number_string_round_trips, write_quoted_str,
 };
 
-// NOTE: This is a temporary compatibility flag for Prettier's pre-#18405 behavior,
-// which should be removed after updating `prettier@3.9.0`.
-const COMPAT_PRE_18405: bool = true;
-
 /// Top-level wrapper around an [`Expression`] for the `json-stringify` variant.
 /// The counterpart of [`super::FmtJsonValue`]; recursion stays within this type.
 pub struct FmtJsonStringifyValue<'a, 'b> {
@@ -42,7 +38,7 @@ impl<'a> Format<'a, JsonFormatContext<'a>> for FmtJsonStringifyValue<'a, '_> {
             Expression::BooleanLiteral(lit) => {
                 write!(f, if lit.value { "true" } else { "false" });
             }
-            Expression::NumericLiteral(lit) => write_number_value(lit, f),
+            Expression::NumericLiteral(lit) => write_number(lit, f),
             Expression::StringLiteral(lit) => write_string(lit, f),
             Expression::ArrayExpression(array) => write_array(array, f),
             Expression::ObjectExpression(object) => write_object(object, f),
@@ -70,31 +66,14 @@ impl<'a> Format<'a, JsonFormatContext<'a>> for FmtJsonStringifyValue<'a, '_> {
     }
 }
 
-fn write_number_value<'a>(lit: &NumericLiteral<'a>, f: &mut JsonFormatter<'_, 'a>) {
-    if COMPAT_PRE_18405 {
-        // The parser can only produce non-negative values; overflow yields +Infinity.
-        if lit.value.is_finite() {
-            // Stack-format then copy once into the arena (same as `oxc_codegen`),
-            // avoiding `ToJsString`'s intermediate heap `String`.
-            let mut buffer = dragonbox_ecma::Buffer::new();
-            write!(f, text(f.allocator().alloc_str(buffer.format(lit.value))));
-        } else {
-            write!(f, "null");
-        }
-    } else {
-        let raw = lit.raw.as_ref().unwrap_or_else(|| unreachable!("parser always sets `raw`"));
-        write!(f, text(raw.as_str()));
-    }
+fn write_number<'a>(lit: &NumericLiteral<'a>, f: &mut JsonFormatter<'_, 'a>) {
+    let raw = lit.raw.as_ref().unwrap_or_else(|| unreachable!("parser always sets `raw`"));
+    write!(f, text(raw.as_str()));
 }
 
 fn write_string<'a>(lit: &StringLiteral<'a>, f: &mut JsonFormatter<'_, 'a>) {
-    if COMPAT_PRE_18405 {
-        let body = json_stringify_escape(lit.value.as_str(), lit.lone_surrogates);
-        write_quoted_str(f, b'"', arena_cow_str(&body, f));
-    } else {
-        // `preferred_quote` already pins `json-stringify` to `"`.
-        FmtJsonString { lit }.fmt(f);
-    }
+    // `preferred_quote` already pins `json-stringify` to `"`.
+    FmtJsonString { lit }.fmt(f);
 }
 
 /// The always-expanded layout shared by arrays and objects: a [`block_indent`]
@@ -165,8 +144,7 @@ fn write_object<'a>(object: &ObjectExpression<'a>, f: &mut JsonFormatter<'_, 'a>
 /// - Identifier key (`a:`, `undefined:`): always double-quoted
 ///   (identifier names cannot contain characters `JSON.stringify` would escape)
 /// - Numeric key: see the module table for the mode split; in compat mode `String()`
-///   (unlike value position's `JSON.stringify()`) has no `null` fallback,
-///   so non-finite quotes as `"Infinity"`
+///   (unlike value position's `JSON.stringify()`) has no `null` fallback, so non-finite quotes as `"Infinity"`
 fn write_object_key<'a>(key: &PropertyKey<'a>, f: &mut JsonFormatter<'_, 'a>) {
     match key {
         PropertyKey::StringLiteral(lit) => write_string(lit, f),
@@ -174,23 +152,12 @@ fn write_object_key<'a>(key: &PropertyKey<'a>, f: &mut JsonFormatter<'_, 'a>) {
             write_quoted_str(f, b'"', ident.name.as_str());
         }
         PropertyKey::NumericLiteral(lit) => {
-            if COMPAT_PRE_18405 {
-                let printed = if lit.value.is_finite() {
-                    let mut buffer = dragonbox_ecma::Buffer::new();
-                    f.allocator().alloc_str(buffer.format(lit.value))
-                } else {
-                    "Infinity"
-                };
-                write_quoted_str(f, b'"', printed);
+            let raw = lit.raw.as_ref().unwrap_or_else(|| unreachable!("parser always sets `raw`"));
+            let raw = raw.as_str();
+            if number_string_round_trips(raw) {
+                write_quoted_str(f, b'"', raw);
             } else {
-                let raw =
-                    lit.raw.as_ref().unwrap_or_else(|| unreachable!("parser always sets `raw`"));
-                let raw = raw.as_str();
-                if number_string_round_trips(raw) {
-                    write_quoted_str(f, b'"', raw);
-                } else {
-                    write!(f, text(raw));
-                }
+                write!(f, text(raw));
             }
         }
         _ => write!(f, FormatInvalidJson(key.span())),
@@ -285,8 +252,6 @@ fn json_stringify_escape(content: &str, lone_surrogates: bool) -> Cow<'_, str> {
 mod tests {
     use super::{json_stringify_escape, number_string_round_trips};
 
-    /// Covers the prettier@3.9 behavior even while `COMPAT_PRE_18405` keeps it inactive,
-    /// so the path doesn't rot before the switch is flipped.
     #[test]
     fn key_round_trip() {
         // Quoted: survives `String(Number(raw))` unchanged

crates/oxc_formatter_json/tests/fixtures/json-stringify/always_expand.json.snap

@@ -19,8 +19,8 @@ source: crates/oxc_formatter_json/tests/fixtures/mod.rs
       1,
       2,
       "3",
-      10000000000,
-      0.001
+      1e10,
+      1e-3
     ]
   },
   "empty_arr": [],
@@ -41,8 +41,8 @@ source: crates/oxc_formatter_json/tests/fixtures/mod.rs
       1,
       2,
       "3",
-      10000000000,
-      0.001
+      1e10,
+      1e-3
     ]
   },
   "empty_arr": [],

crates/oxc_formatter_json/tests/fixtures/json-stringify/numbers.json.snap

@@ -15,18 +15,18 @@ source: crates/oxc_formatter_json/tests/fixtures/mod.rs
 ---------------------------------------------
 [
   0.5,
-  0.8675309,
-  8675309,
-  912559,
-  1,
-  2,
-  2,
-  1,
-  1,
-  -9876.54321,
-  1.23456789e+34,
-  2.3456789012e+76,
-  123456,
+  .8675309,
+  8675309.,
+  0xdecaf,
+  1e00,
+  2e+00,
+  2e-00,
+  1.0,
+  1.00000,
+  -9876.543210,
+  1.234567890E+34,
+  23456789012E66,
+  123_456,
   1,
   -1,
   0.5,
@@ -42,18 +42,18 @@ source: crates/oxc_formatter_json/tests/fixtures/mod.rs
 ----------------------------------------------
 [
   0.5,
-  0.8675309,
-  8675309,
-  912559,
-  1,
-  2,
-  2,
-  1,
-  1,
-  -9876.54321,
-  1.23456789e+34,
-  2.3456789012e+76,
-  123456,
+  .8675309,
+  8675309.,
+  0xdecaf,
+  1e00,
+  2e+00,
+  2e-00,
+  1.0,
+  1.00000,
+  -9876.543210,
+  1.234567890E+34,
+  23456789012E66,
+  123_456,
   1,
   -1,
   0.5,

crates/oxc_formatter_json/tests/fixtures/json-stringify/property_key.json.snap

@@ -31,15 +31,15 @@ source: crates/oxc_formatter_json/tests/fixtures/mod.rs
   "undefined": "",
   "string": "",
   "0": "",
-  "100": "",
-  "100": "",
+  1e2: "",
+  1.0e+2: "",
+  .1: "",
   "0.1": "",
-  "0.1": "",
-  "1": "",
-  "1": "",
-  "16": "",
-  "1e+30": "",
-  "123": ""
+  1.0: "",
+  1.00000: "",
+  0x10: "",
+  999999999999999999999999999999: "",
+  1_2_3: ""
 }
 
 ----------------------------------------------
@@ -52,15 +52,15 @@ source: crates/oxc_formatter_json/tests/fixtures/mod.rs
   "undefined": "",
   "string": "",
   "0": "",
-  "100": "",
-  "100": "",
+  1e2: "",
+  1.0e+2: "",
+  .1: "",
   "0.1": "",
-  "0.1": "",
-  "1": "",
-  "1": "",
-  "16": "",
-  "1e+30": "",
-  "123": ""
+  1.0: "",
+  1.00000: "",
+  0x10: "",
+  999999999999999999999999999999: "",
+  1_2_3: ""
 }
 
 ===================== End =====================

crates/oxc_formatter_json/tests/fixtures/json-stringify/strings.json.snap

@@ -23,7 +23,7 @@ source: crates/oxc_formatter_json/tests/fixtures/mod.rs
   "single",
   "double",
   "I can use \"double quotes\" here",
-  "ģ䕧 ÿ \u0000 / /",
+  "ģ䕧 \xFF \0 / \/",
   "",
   "foo",
   "\n  multiple-line\n",
@@ -37,7 +37,7 @@ source: crates/oxc_formatter_json/tests/fixtures/mod.rs
   "single",
   "double",
   "I can use \"double quotes\" here",
-  "ģ䕧 ÿ \u0000 / /",
+  "ģ䕧 \xFF \0 / \/",
   "",
   "foo",
   "\n  multiple-line\n",

tasks/prettier_conformance/snapshots/prettier.json-stringify.snap.md

@@ -1,12 +1,6 @@
-json-stringify compatibility: 8/14 (57.14%), 0 files skipped
+json-stringify compatibility: 14/14 (100.00%), 0 files skipped
 
 # Failed
 
 | Spec path | Failed or Passed | Match ratio |
 | :-------- | :--------------: | :---------: |
-| json/json/json5.json | 💥 | 82.35% |
-| json/json/json6.json | 💥 | 77.91% |
-| json/json/multi-line.json | 💥 | 87.50% |
-| json/json/pass1.json | 💥 | 81.33% |
-| json/json/propertyKey.json | 💥 | 33.33% |
-| json/json/single-line.json | 💥 | 87.50% |