nu_command/formats/from/
json.rs

1use std::io::{BufRead, Cursor};
2
3use nu_engine::command_prelude::*;
4use nu_protocol::{shell_error::io::IoError, ListStream, Signals};
5
6#[derive(Clone)]
7pub struct FromJson;
8
9impl Command for FromJson {
10    fn name(&self) -> &str {
11        "from json"
12    }
13
14    fn description(&self) -> &str {
15        "Convert from json to structured data."
16    }
17
18    fn signature(&self) -> nu_protocol::Signature {
19        Signature::build("from json")
20            .input_output_types(vec![(Type::String, Type::Any)])
21            .switch("objects", "treat each line as a separate value", Some('o'))
22            .switch("strict", "follow the json specification exactly", Some('s'))
23            .category(Category::Formats)
24    }
25
26    fn examples(&self) -> Vec<Example> {
27        vec![
28            Example {
29                example: r#"'{ "a": 1 }' | from json"#,
30                description: "Converts json formatted string to table",
31                result: Some(Value::test_record(record! {
32                    "a" => Value::test_int(1),
33                })),
34            },
35            Example {
36                example: r#"'{ "a": 1, "b": [1, 2] }' | from json"#,
37                description: "Converts json formatted string to table",
38                result: Some(Value::test_record(record! {
39                    "a" => Value::test_int(1),
40                    "b" => Value::test_list(vec![Value::test_int(1), Value::test_int(2)]),
41                })),
42            },
43            Example {
44                example: r#"'{ "a": 1, "b": 2 }' | from json -s"#,
45                description: "Parse json strictly which will error on comments and trailing commas",
46                result: Some(Value::test_record(record! {
47                    "a" => Value::test_int(1),
48                    "b" => Value::test_int(2),
49                })),
50            },
51            Example {
52                example: r#"'{ "a": 1 }
53{ "b": 2 }' | from json --objects"#,
54                description: "Parse a stream of line-delimited JSON values",
55                result: Some(Value::test_list(vec![
56                    Value::test_record(record! {"a" => Value::test_int(1)}),
57                    Value::test_record(record! {"b" => Value::test_int(2)}),
58                ])),
59            },
60        ]
61    }
62
63    fn run(
64        &self,
65        engine_state: &EngineState,
66        stack: &mut Stack,
67        call: &Call,
68        input: PipelineData,
69    ) -> Result<PipelineData, ShellError> {
70        let span = call.head;
71
72        let strict = call.has_flag(engine_state, stack, "strict")?;
73        let metadata = input.metadata().map(|md| md.with_content_type(None));
74
75        // TODO: turn this into a structured underline of the nu_json error
76        if call.has_flag(engine_state, stack, "objects")? {
77            // Return a stream of JSON values, one for each non-empty line
78            match input {
79                PipelineData::Value(Value::String { val, .. }, ..) => Ok(PipelineData::ListStream(
80                    read_json_lines(
81                        Cursor::new(val),
82                        span,
83                        strict,
84                        engine_state.signals().clone(),
85                    ),
86                    metadata,
87                )),
88                PipelineData::ByteStream(stream, ..)
89                    if stream.type_() != ByteStreamType::Binary =>
90                {
91                    if let Some(reader) = stream.reader() {
92                        Ok(PipelineData::ListStream(
93                            read_json_lines(reader, span, strict, Signals::empty()),
94                            metadata,
95                        ))
96                    } else {
97                        Ok(PipelineData::Empty)
98                    }
99                }
100                _ => Err(ShellError::OnlySupportsThisInputType {
101                    exp_input_type: "string".into(),
102                    wrong_type: input.get_type().to_string(),
103                    dst_span: call.head,
104                    src_span: input.span().unwrap_or(call.head),
105                }),
106            }
107        } else {
108            // Return a single JSON value
109            let (string_input, span, ..) = input.collect_string_strict(span)?;
110
111            if string_input.is_empty() {
112                return Ok(Value::nothing(span).into_pipeline_data());
113            }
114
115            if strict {
116                Ok(convert_string_to_value_strict(&string_input, span)?
117                    .into_pipeline_data_with_metadata(metadata))
118            } else {
119                Ok(convert_string_to_value(&string_input, span)?
120                    .into_pipeline_data_with_metadata(metadata))
121            }
122        }
123    }
124}
125
126/// Create a stream of values from a reader that produces line-delimited JSON
127fn read_json_lines(
128    input: impl BufRead + Send + 'static,
129    span: Span,
130    strict: bool,
131    signals: Signals,
132) -> ListStream {
133    let iter = input
134        .lines()
135        .filter(|line| line.as_ref().is_ok_and(|line| !line.trim().is_empty()) || line.is_err())
136        .map(move |line| {
137            let line = line.map_err(|err| IoError::new(err.kind(), span, None))?;
138            if strict {
139                convert_string_to_value_strict(&line, span)
140            } else {
141                convert_string_to_value(&line, span)
142            }
143        })
144        .map(move |result| result.unwrap_or_else(|err| Value::error(err, span)));
145
146    ListStream::new(iter, span, signals)
147}
148
149fn convert_nujson_to_value(value: nu_json::Value, span: Span) -> Value {
150    match value {
151        nu_json::Value::Array(array) => Value::list(
152            array
153                .into_iter()
154                .map(|x| convert_nujson_to_value(x, span))
155                .collect(),
156            span,
157        ),
158        nu_json::Value::Bool(b) => Value::bool(b, span),
159        nu_json::Value::F64(f) => Value::float(f, span),
160        nu_json::Value::I64(i) => Value::int(i, span),
161        nu_json::Value::Null => Value::nothing(span),
162        nu_json::Value::Object(k) => Value::record(
163            k.into_iter()
164                .map(|(k, v)| (k, convert_nujson_to_value(v, span)))
165                .collect(),
166            span,
167        ),
168        nu_json::Value::U64(u) => {
169            if u > i64::MAX as u64 {
170                Value::error(
171                    ShellError::CantConvert {
172                        to_type: "i64 sized integer".into(),
173                        from_type: "value larger than i64".into(),
174                        span,
175                        help: None,
176                    },
177                    span,
178                )
179            } else {
180                Value::int(u as i64, span)
181            }
182        }
183        nu_json::Value::String(s) => Value::string(s, span),
184    }
185}
186
187fn convert_string_to_value(string_input: &str, span: Span) -> Result<Value, ShellError> {
188    match nu_json::from_str(string_input) {
189        Ok(value) => Ok(convert_nujson_to_value(value, span)),
190
191        Err(x) => match x {
192            nu_json::Error::Syntax(_, row, col) => {
193                let label = x.to_string();
194                let label_span = Span::from_row_column(row, col, string_input);
195                Err(ShellError::GenericError {
196                    error: "Error while parsing JSON text".into(),
197                    msg: "error parsing JSON text".into(),
198                    span: Some(span),
199                    help: None,
200                    inner: vec![ShellError::OutsideSpannedLabeledError {
201                        src: string_input.into(),
202                        error: "Error while parsing JSON text".into(),
203                        msg: label,
204                        span: label_span,
205                    }],
206                })
207            }
208            x => Err(ShellError::CantConvert {
209                to_type: format!("structured json data ({x})"),
210                from_type: "string".into(),
211                span,
212                help: None,
213            }),
214        },
215    }
216}
217
218fn convert_string_to_value_strict(string_input: &str, span: Span) -> Result<Value, ShellError> {
219    match serde_json::from_str(string_input) {
220        Ok(value) => Ok(convert_nujson_to_value(value, span)),
221        Err(err) => Err(if err.is_syntax() {
222            let label = err.to_string();
223            let label_span = Span::from_row_column(err.line(), err.column(), string_input);
224            ShellError::GenericError {
225                error: "Error while parsing JSON text".into(),
226                msg: "error parsing JSON text".into(),
227                span: Some(span),
228                help: None,
229                inner: vec![ShellError::OutsideSpannedLabeledError {
230                    src: string_input.into(),
231                    error: "Error while parsing JSON text".into(),
232                    msg: label,
233                    span: label_span,
234                }],
235            }
236        } else {
237            ShellError::CantConvert {
238                to_type: format!("structured json data ({err})"),
239                from_type: "string".into(),
240                span,
241                help: None,
242            }
243        }),
244    }
245}
246
247#[cfg(test)]
248mod test {
249    use nu_cmd_lang::eval_pipeline_without_terminal_expression;
250
251    use crate::{Metadata, MetadataSet};
252
253    use super::*;
254
255    #[test]
256    fn test_examples() {
257        use crate::test_examples;
258
259        test_examples(FromJson {})
260    }
261
262    #[test]
263    fn test_content_type_metadata() {
264        let mut engine_state = Box::new(EngineState::new());
265        let delta = {
266            let mut working_set = StateWorkingSet::new(&engine_state);
267
268            working_set.add_decl(Box::new(FromJson {}));
269            working_set.add_decl(Box::new(Metadata {}));
270            working_set.add_decl(Box::new(MetadataSet {}));
271
272            working_set.render()
273        };
274
275        engine_state
276            .merge_delta(delta)
277            .expect("Error merging delta");
278
279        let cmd = r#"'{"a":1,"b":2}' | metadata set --content-type 'application/json' --datasource-ls | from json | metadata | $in"#;
280        let result = eval_pipeline_without_terminal_expression(
281            cmd,
282            std::env::temp_dir().as_ref(),
283            &mut engine_state,
284        );
285        assert_eq!(
286            Value::test_record(record!("source" => Value::test_string("ls"))),
287            result.expect("There should be a result")
288        )
289    }
290}
nu_command/formats/from/json.rs

nu_command/formats/from/
json.rs
