nu_plugin_core/serializers/
json.rs

1use nu_plugin_protocol::{PluginInput, PluginOutput};
2use nu_protocol::{
3    ShellError,
4    shell_error::{self, io::IoError},
5};
6use serde::Deserialize;
7
8use crate::{Encoder, PluginEncoder};
9
10/// A `PluginEncoder` that enables the plugin to communicate with Nushell with JSON
11/// serialized data.
12///
13/// Each message in the stream is followed by a newline when serializing, but is not required for
14/// deserialization. The output is not pretty printed and each object does not contain newlines.
15/// If it is more convenient, a plugin may choose to separate messages by newline.
16#[derive(Clone, Copy, Debug)]
17pub struct JsonSerializer;
18
19impl PluginEncoder for JsonSerializer {
20    fn name(&self) -> &str {
21        "json"
22    }
23}
24
25impl Encoder<PluginInput> for JsonSerializer {
26    fn encode(
27        &self,
28        plugin_input: &PluginInput,
29        writer: &mut impl std::io::Write,
30    ) -> Result<(), nu_protocol::ShellError> {
31        serde_json::to_writer(&mut *writer, plugin_input).map_err(json_encode_err)?;
32        writer.write_all(b"\n").map_err(|err| {
33            ShellError::Io(IoError::new_internal(
34                err,
35                "Failed to write final line break",
36            ))
37        })
38    }
39
40    fn decode(
41        &self,
42        reader: &mut impl std::io::BufRead,
43    ) -> Result<Option<PluginInput>, nu_protocol::ShellError> {
44        let mut de = serde_json::Deserializer::from_reader(reader);
45        PluginInput::deserialize(&mut de)
46            .map(Some)
47            .or_else(json_decode_err)
48    }
49}
50
51impl Encoder<PluginOutput> for JsonSerializer {
52    fn encode(
53        &self,
54        plugin_output: &PluginOutput,
55        writer: &mut impl std::io::Write,
56    ) -> Result<(), ShellError> {
57        serde_json::to_writer(&mut *writer, plugin_output).map_err(json_encode_err)?;
58        writer.write_all(b"\n").map_err(|err| {
59            ShellError::Io(IoError::new_internal(
60                err,
61                "JsonSerializer could not encode linebreak",
62            ))
63        })
64    }
65
66    fn decode(
67        &self,
68        reader: &mut impl std::io::BufRead,
69    ) -> Result<Option<PluginOutput>, ShellError> {
70        let mut de = serde_json::Deserializer::from_reader(reader);
71        PluginOutput::deserialize(&mut de)
72            .map(Some)
73            .or_else(json_decode_err)
74    }
75}
76
77/// Handle a `serde_json` encode error.
78fn json_encode_err(err: serde_json::Error) -> ShellError {
79    if err.is_io() {
80        ShellError::Io(IoError::new_internal(
81            shell_error::io::ErrorKind::from_std(err.io_error_kind().expect("is io")),
82            "Could not encode with json",
83        ))
84    } else {
85        ShellError::PluginFailedToEncode {
86            msg: err.to_string(),
87        }
88    }
89}
90
91/// Handle a `serde_json` decode error. Returns `Ok(None)` on eof.
92fn json_decode_err<T>(err: serde_json::Error) -> Result<Option<T>, ShellError> {
93    if err.is_eof() {
94        Ok(None)
95    } else if err.is_io() {
96        Err(ShellError::Io(IoError::new_internal(
97            shell_error::io::ErrorKind::from_std(err.io_error_kind().expect("is io")),
98            "Could not decode with json",
99        )))
100    } else {
101        Err(ShellError::PluginFailedToDecode {
102            msg: err.to_string(),
103        })
104    }
105}
106
107#[cfg(test)]
108mod tests {
109    use super::*;
110    crate::serializers::tests::generate_tests!(JsonSerializer {});
111
112    #[test]
113    fn json_ends_in_newline() {
114        let mut out = vec![];
115        JsonSerializer {}
116            .encode(&PluginInput::Call(0, PluginCall::Signature), &mut out)
117            .expect("serialization error");
118        let string = std::str::from_utf8(&out).expect("utf-8 error");
119        assert!(
120            string.ends_with('\n'),
121            "doesn't end with newline: {string:?}"
122        );
123    }
124
125    #[test]
126    fn json_has_no_other_newlines() {
127        let mut out = vec![];
128        // use something deeply nested, to try to trigger any pretty printing
129        let output = PluginOutput::Data(
130            0,
131            StreamData::List(Value::test_list(vec![
132                Value::test_int(4),
133                // in case escaping failed
134                Value::test_string("newline\ncontaining\nstring"),
135            ])),
136        );
137        JsonSerializer {}
138            .encode(&output, &mut out)
139            .expect("serialization error");
140        let string = std::str::from_utf8(&out).expect("utf-8 error");
141        assert_eq!(1, string.chars().filter(|ch| *ch == '\n').count());
142    }
143}
nu_plugin_core/serializers/json.rs

nu_plugin_core/serializers/
json.rs
