Serde Knowledge Patch Skill

Serde Knowledge Patch

Covers serde_json 1.0.129–1.0.143 (Nov 2024 – Aug 2025). Claude Opus 4.6 knows serde through 1.0.200 and serde_json through 1.0.128.

Index

| Topic | Reference | Key features | |---|---|---| | Map operations | references/map-operations.md | sort_keys, sort_all_objects, Map as Deserializer, FromStr for Map | | RawValue | references/rawvalue.md | NULL, TRUE, FALSE associated constants |

Quick Reference — New serde_json APIs

| API | Version | What it does | |---|---|---| | Map::sort_keys() | 1.0.129 | Sort map keys alphabetically in place | | Value::sort_all_objects() | 1.0.129 | Recursively sort all nested object keys | | Map<String, Value>: Deserializer | 1.0.131 | Deserialize structs directly from a map | | &Map<String, Value>: IntoDeserializer | 1.0.131 | Use &map with Deserialize::deserialize | | RawValue::NULL | 1.0.134 | Associated constant for raw "null" | | RawValue::TRUE | 1.0.134 | Associated constant for raw "true" | | RawValue::FALSE | 1.0.134 | Associated constant for raw "false" | | Map<String, Value>: FromStr | 1.0.143 | Parse JSON string into a Map via .parse() |

Essential Patterns (inline)

Sort JSON keys — deterministic output

use serde_json::{Map, Value, json};

// Sort a single map's keys
let mut map: Map<String, Value> = serde_json::from_str(r#"{"z":1,"a":2}"#)?;
map.sort_keys();
// map is now {"a":2,"z":1}

// Recursively sort all nested objects
let mut value = json!({"z": {"c": 1, "a": 2}, "a": 3});
value.sort_all_objects();
// {"a":3,"z":{"a":2,"c":1}}

Use sort_all_objects() before serializing when you need deterministic JSON output (e.g., for hashing, diffing, or snapshot tests).

Deserialize struct directly from a Map

use serde::Deserialize;
use serde_json::{Map, Value};

#[derive(Deserialize)]
struct Config { name: String, count: u32 }

let map: Map<String, Value> = serde_json::from_str(r#"{"name":"x","count":5}"#)?;
let config = Config::deserialize(&map)?;

Avoids the round-trip through Value when you already have a Map. Works with both owned Map and &Map.

RawValue associated constants

use serde_json::value::RawValue;

let null: &RawValue = RawValue::NULL;   // raw "null"
let t: &RawValue = RawValue::TRUE;      // raw "true"
let f: &RawValue = RawValue::FALSE;     // raw "false"

Useful when constructing partial JSON responses or default values without allocation.

Parse JSON string directly into a Map

use serde_json::Map;

let map: Map<String, serde_json::Value> = r#"{"a":1}"#.parse()?;

Shorthand for serde_json::from_str when you know the top-level value is an object.

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