1/// Construct a `serde_json::Value` from a JSON literal.
2///
3/// ```
4/// # use serde_json::json;
5/// #
6/// let value = json!({
7/// "code": 200,
8/// "success": true,
9/// "payload": {
10/// "features": [
11/// "serde",
12/// "json"
13/// ],
14/// "homepage": null
15/// }
16/// });
17/// ```
18///
19/// Variables or expressions can be interpolated into the JSON literal. Any type
20/// interpolated into an array element or object value must implement Serde's
21/// `Serialize` trait, while any type interpolated into a object key must
22/// implement `Into<String>`. If the `Serialize` implementation of the
23/// interpolated type decides to fail, or if the interpolated type contains a
24/// map with non-string keys, the `json!` macro will panic.
25///
26/// ```
27/// # use serde_json::json;
28/// #
29/// let code = 200;
30/// let features = vec!["serde", "json"];
31///
32/// let value = json!({
33/// "code": code,
34/// "success": code == 200,
35/// "payload": {
36/// features[0]: features[1]
37/// }
38/// });
39/// ```
40///
41/// Trailing commas are allowed inside both arrays and objects.
42///
43/// ```
44/// # use serde_json::json;
45/// #
46/// let value = json!([
47/// "notice",
48/// "the",
49/// "trailing",
50/// "comma -->",
51/// ]);
52/// ```
53#[macro_export]
54macro_rules! json {
55 // Hide distracting implementation details from the generated rustdoc.
56 ($($json:tt)+) => {
57 $crate::json_internal!($($json)+)
58 };
59}
60
61// Rocket relies on this because they export their own `json!` with a different
62// doc comment than ours, and various Rust bugs prevent them from calling our
63// `json!` from their `json!` so they call `json_internal!` directly. Check with
64// @SergioBenitez before making breaking changes to this macro.
65//
66// Changes are fine as long as `json_internal!` does not call any new helper
67// macros and can still be invoked as `json_internal!($($json)+)`.
68#[macro_export]
69#[doc(hidden)]
70macro_rules! json_internal {
71 //////////////////////////////////////////////////////////////////////////
72 // TT muncher for parsing the inside of an array [...]. Produces a vec![...]
73 // of the elements.
74 //
75 // Must be invoked as: json_internal!(@array [] $($tt)*)
76 //////////////////////////////////////////////////////////////////////////
77
78 // Done with trailing comma.
79 (@array [$($elems:expr,)*]) => {
80 $crate::__private::vec![$($elems,)*]
81 };
82
83 // Done without trailing comma.
84 (@array [$($elems:expr),*]) => {
85 $crate::__private::vec![$($elems),*]
86 };
87
88 // Next element is `null`.
89 (@array [$($elems:expr,)*] null $($rest:tt)*) => {
90 $crate::json_internal!(@array [$($elems,)* $crate::json_internal!(null)] $($rest)*)
91 };
92
93 // Next element is `true`.
94 (@array [$($elems:expr,)*] true $($rest:tt)*) => {
95 $crate::json_internal!(@array [$($elems,)* $crate::json_internal!(true)] $($rest)*)
96 };
97
98 // Next element is `false`.
99 (@array [$($elems:expr,)*] false $($rest:tt)*) => {
100 $crate::json_internal!(@array [$($elems,)* $crate::json_internal!(false)] $($rest)*)
101 };
102
103 // Next element is an array.
104 (@array [$($elems:expr,)*] [$($array:tt)*] $($rest:tt)*) => {
105 $crate::json_internal!(@array [$($elems,)* $crate::json_internal!([$($array)*])] $($rest)*)
106 };
107
108 // Next element is a map.
109 (@array [$($elems:expr,)*] {$($map:tt)*} $($rest:tt)*) => {
110 $crate::json_internal!(@array [$($elems,)* $crate::json_internal!({$($map)*})] $($rest)*)
111 };
112
113 // Next element is an expression followed by comma.
114 (@array [$($elems:expr,)*] $next:expr, $($rest:tt)*) => {
115 $crate::json_internal!(@array [$($elems,)* $crate::json_internal!($next),] $($rest)*)
116 };
117
118 // Last element is an expression with no trailing comma.
119 (@array [$($elems:expr,)*] $last:expr) => {
120 $crate::json_internal!(@array [$($elems,)* $crate::json_internal!($last)])
121 };
122
123 // Comma after the most recent element.
124 (@array [$($elems:expr),*] , $($rest:tt)*) => {
125 $crate::json_internal!(@array [$($elems,)*] $($rest)*)
126 };
127
128 // Unexpected token after most recent element.
129 (@array [$($elems:expr),*] $unexpected:tt $($rest:tt)*) => {
130 $crate::json_unexpected!($unexpected)
131 };
132
133 //////////////////////////////////////////////////////////////////////////
134 // TT muncher for parsing the inside of an object {...}. Each entry is
135 // inserted into the given map variable.
136 //
137 // Must be invoked as: json_internal!(@object $map () ($($tt)*) ($($tt)*))
138 //
139 // We require two copies of the input tokens so that we can match on one
140 // copy and trigger errors on the other copy.
141 //////////////////////////////////////////////////////////////////////////
142
143 // Done.
144 (@object $object:ident () () ()) => {};
145
146 // Insert the current entry followed by trailing comma.
147 (@object $object:ident [$($key:tt)+] ($value:expr) , $($rest:tt)*) => {
148 let _ = $object.insert(($($key)+).into(), $value);
149 $crate::json_internal!(@object $object () ($($rest)*) ($($rest)*));
150 };
151
152 // Current entry followed by unexpected token.
153 (@object $object:ident [$($key:tt)+] ($value:expr) $unexpected:tt $($rest:tt)*) => {
154 $crate::json_unexpected!($unexpected);
155 };
156
157 // Insert the last entry without trailing comma.
158 (@object $object:ident [$($key:tt)+] ($value:expr)) => {
159 let _ = $object.insert(($($key)+).into(), $value);
160 };
161
162 // Next value is `null`.
163 (@object $object:ident ($($key:tt)+) (: null $($rest:tt)*) $copy:tt) => {
164 $crate::json_internal!(@object $object [$($key)+] ($crate::json_internal!(null)) $($rest)*);
165 };
166
167 // Next value is `true`.
168 (@object $object:ident ($($key:tt)+) (: true $($rest:tt)*) $copy:tt) => {
169 $crate::json_internal!(@object $object [$($key)+] ($crate::json_internal!(true)) $($rest)*);
170 };
171
172 // Next value is `false`.
173 (@object $object:ident ($($key:tt)+) (: false $($rest:tt)*) $copy:tt) => {
174 $crate::json_internal!(@object $object [$($key)+] ($crate::json_internal!(false)) $($rest)*);
175 };
176
177 // Next value is an array.
178 (@object $object:ident ($($key:tt)+) (: [$($array:tt)*] $($rest:tt)*) $copy:tt) => {
179 $crate::json_internal!(@object $object [$($key)+] ($crate::json_internal!([$($array)*])) $($rest)*);
180 };
181
182 // Next value is a map.
183 (@object $object:ident ($($key:tt)+) (: {$($map:tt)*} $($rest:tt)*) $copy:tt) => {
184 $crate::json_internal!(@object $object [$($key)+] ($crate::json_internal!({$($map)*})) $($rest)*);
185 };
186
187 // Next value is an expression followed by comma.
188 (@object $object:ident ($($key:tt)+) (: $value:expr , $($rest:tt)*) $copy:tt) => {
189 $crate::json_internal!(@object $object [$($key)+] ($crate::json_internal!($value)) , $($rest)*);
190 };
191
192 // Last value is an expression with no trailing comma.
193 (@object $object:ident ($($key:tt)+) (: $value:expr) $copy:tt) => {
194 $crate::json_internal!(@object $object [$($key)+] ($crate::json_internal!($value)));
195 };
196
197 // Missing value for last entry. Trigger a reasonable error message.
198 (@object $object:ident ($($key:tt)+) (:) $copy:tt) => {
199 // "unexpected end of macro invocation"
200 $crate::json_internal!();
201 };
202
203 // Missing colon and value for last entry. Trigger a reasonable error
204 // message.
205 (@object $object:ident ($($key:tt)+) () $copy:tt) => {
206 // "unexpected end of macro invocation"
207 $crate::json_internal!();
208 };
209
210 // Misplaced colon. Trigger a reasonable error message.
211 (@object $object:ident () (: $($rest:tt)*) ($colon:tt $($copy:tt)*)) => {
212 // Takes no arguments so "no rules expected the token `:`".
213 $crate::json_unexpected!($colon);
214 };
215
216 // Found a comma inside a key. Trigger a reasonable error message.
217 (@object $object:ident ($($key:tt)*) (, $($rest:tt)*) ($comma:tt $($copy:tt)*)) => {
218 // Takes no arguments so "no rules expected the token `,`".
219 $crate::json_unexpected!($comma);
220 };
221
222 // Key is fully parenthesized. This avoids clippy double_parens false
223 // positives because the parenthesization may be necessary here.
224 (@object $object:ident () (($key:expr) : $($rest:tt)*) $copy:tt) => {
225 $crate::json_internal!(@object $object ($key) (: $($rest)*) (: $($rest)*));
226 };
227
228 // Refuse to absorb colon token into key expression.
229 (@object $object:ident ($($key:tt)*) (: $($unexpected:tt)+) $copy:tt) => {
230 $crate::json_expect_expr_comma!($($unexpected)+);
231 };
232
233 // Munch a token into the current key.
234 (@object $object:ident ($($key:tt)*) ($tt:tt $($rest:tt)*) $copy:tt) => {
235 $crate::json_internal!(@object $object ($($key)* $tt) ($($rest)*) ($($rest)*));
236 };
237
238 //////////////////////////////////////////////////////////////////////////
239 // The main implementation.
240 //
241 // Must be invoked as: json_internal!($($json)+)
242 //////////////////////////////////////////////////////////////////////////
243
244 (null) => {
245 $crate::Value::Null
246 };
247
248 (true) => {
249 $crate::Value::Bool(true)
250 };
251
252 (false) => {
253 $crate::Value::Bool(false)
254 };
255
256 ([]) => {
257 $crate::Value::Array($crate::__private::vec![])
258 };
259
260 ([ $($tt:tt)+ ]) => {
261 $crate::Value::Array($crate::json_internal!(@array [] $($tt)+))
262 };
263
264 ({}) => {
265 $crate::Value::Object($crate::Map::new())
266 };
267
268 ({ $($tt:tt)+ }) => {
269 $crate::Value::Object({
270 let mut object = $crate::Map::new();
271 $crate::json_internal!(@object object () ($($tt)+) ($($tt)+));
272 object
273 })
274 };
275
276 // Any Serialize type: numbers, strings, struct literals, variables etc.
277 // Must be below every other rule.
278 ($other:expr) => {
279 $crate::to_value(&$other).unwrap()
280 };
281}
282
283// Used by old versions of Rocket.
284// Unused since https://github.com/rwf2/Rocket/commit/c74bcfd40a47b35330db6cafb88e4f3da83e0d17
285#[macro_export]
286#[doc(hidden)]
287macro_rules! json_internal_vec {
288 ($($content:tt)*) => {
289 vec![$($content)*]
290 };
291}
292
293#[macro_export]
294#[doc(hidden)]
295macro_rules! json_unexpected {
296 () => {};
297}
298
299#[macro_export]
300#[doc(hidden)]
301macro_rules! json_expect_expr_comma {
302 ($e:expr , $($tt:tt)*) => {};
303}
304