1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
use nu_engine::CallExt;
use nu_protocol::ast::{Call, CellPath, PathMember};
use nu_protocol::engine::{Command, EngineState, Stack};
use nu_protocol::{
Category, Example, IntoInterruptiblePipelineData, IntoPipelineData, PipelineData,
PipelineIterator, ShellError, Signature, Span, SyntaxShape, Type, Value,
};
use std::collections::HashSet;
#[derive(Clone)]
pub struct Select;
impl Command for Select {
fn name(&self) -> &str {
"select"
}
fn signature(&self) -> Signature {
Signature::build("select")
.input_output_types(vec![
(Type::Record(vec![]), Type::Record(vec![])),
(Type::Table(vec![]), Type::Table(vec![])),
])
.switch(
"ignore-errors",
"when an error occurs, instead of erroring out, suppress the error message",
Some('i'),
)
.rest(
"rest",
SyntaxShape::CellPath,
"the columns to select from the table",
)
.category(Category::Filters)
}
fn usage(&self) -> &str {
"Select only these columns or rows from the input. Opposite of `reject`."
}
fn extra_usage(&self) -> &str {
r#"This differs from `get` in that, rather than accessing the given value in the data structure,
it removes all non-selected values from the structure. Hence, using `select` on a table will
produce a table, a list will produce a list, and a record will produce a record."#
}
fn search_terms(&self) -> Vec<&str> {
vec!["pick", "choose", "get"]
}
fn run(
&self,
engine_state: &EngineState,
stack: &mut Stack,
call: &Call,
input: PipelineData,
) -> Result<PipelineData, ShellError> {
let columns: Vec<CellPath> = call.rest(engine_state, stack, 0)?;
let span = call.head;
let ignore_errors = call.has_flag("ignore-errors");
select(engine_state, span, columns, input, ignore_errors)
}
fn examples(&self) -> Vec<Example> {
vec![
Example {
description: "Select a column in a table",
example: "[{a: a b: b}] | select a",
result: Some(Value::List {
vals: vec![Value::test_record(vec!["a"], vec![Value::test_string("a")])],
span: Span::test_data(),
}),
},
Example {
description: "Select a field in a record",
example: "{a: a b: b} | select a",
result: Some(Value::test_record(vec!["a"], vec![Value::test_string("a")])),
},
Example {
description: "Select just the `name` column",
example: "ls | select name",
result: None,
},
Example {
description: "Select the first four rows (this is the same as `first 4`)",
example: "ls | select 0 1 2 3",
result: None,
},
]
}
}
fn select(
engine_state: &EngineState,
call_span: Span,
columns: Vec<CellPath>,
input: PipelineData,
ignore_errors: bool,
) -> Result<PipelineData, ShellError> {
let mut unique_rows: HashSet<usize> = HashSet::new();
let mut new_columns = vec![];
for column in columns {
let CellPath { ref members } = column;
match members.get(0) {
Some(PathMember::Int { val, span }) => {
if members.len() > 1 {
if ignore_errors {
return Ok(Value::nothing(call_span).into_pipeline_data());
}
return Err(ShellError::GenericError(
"Select only allows row numbers for rows".into(),
"extra after row number".into(),
Some(*span),
None,
Vec::new(),
));
}
if unique_rows.contains(val) {
return Err(ShellError::GenericError(
"Select can't get the same row twice".into(),
"duplicated row index".into(),
Some(*span),
None,
Vec::new(),
));
}
unique_rows.insert(*val);
}
_ => new_columns.push(column),
};
}
let columns = new_columns;
let mut unique_rows: Vec<usize> = unique_rows.into_iter().collect();
let input = if !unique_rows.is_empty() {
unique_rows.sort_unstable();
let metadata = input.metadata();
let pipeline_iter: PipelineIterator = input.into_iter();
NthIterator {
input: pipeline_iter,
rows: unique_rows,
skip: false,
current: 0,
}
.into_pipeline_data(engine_state.ctrlc.clone())
.set_metadata(metadata)
} else {
input
};
match input {
PipelineData::Value(
Value::List {
vals: input_vals,
span,
},
metadata,
..,
) => {
let mut output = vec![];
let mut columns_with_value = Vec::new();
let mut allempty = true;
for input_val in input_vals {
if !columns.is_empty() {
let mut cols = vec![];
let mut vals = vec![];
for path in &columns {
match input_val.clone().follow_cell_path(
&path.members,
false,
ignore_errors,
) {
Ok(fetcher) => {
allempty = false;
cols.push(path.into_string().replace('.', "_"));
vals.push(fetcher);
if !columns_with_value.contains(&path) {
columns_with_value.push(path);
}
}
Err(e) => {
return Err(e);
}
}
}
output.push(Value::Record { cols, vals, span })
} else {
output.push(input_val)
}
}
if allempty {
Ok(Value::nothing(call_span).into_pipeline_data())
} else {
Ok(output
.into_iter()
.into_pipeline_data(engine_state.ctrlc.clone())
.set_metadata(metadata))
}
}
PipelineData::ListStream(stream, metadata, ..) => {
let mut values = vec![];
for x in stream {
if !columns.is_empty() {
let mut cols = vec![];
let mut vals = vec![];
for path in &columns {
match x
.clone()
.follow_cell_path(&path.members, false, ignore_errors)
{
Ok(value) => {
cols.push(path.into_string().replace('.', "_"));
vals.push(value);
}
Err(e) => return Err(e),
}
}
values.push(Value::Record {
cols,
vals,
span: call_span,
});
} else {
values.push(x);
}
}
Ok(values
.into_pipeline_data(engine_state.ctrlc.clone())
.set_metadata(metadata))
}
PipelineData::Value(v, metadata, ..) => {
if !columns.is_empty() {
let mut cols = vec![];
let mut vals = vec![];
for cell_path in columns {
match v
.clone()
.follow_cell_path(&cell_path.members, false, ignore_errors)
{
Ok(result) => {
cols.push(cell_path.into_string().replace('.', "_"));
vals.push(result);
}
Err(e) => return Err(e),
}
}
Ok(Value::Record {
cols,
vals,
span: call_span,
}
.into_pipeline_data()
.set_metadata(metadata))
} else {
Ok(v.into_pipeline_data().set_metadata(metadata))
}
}
_ => Ok(PipelineData::empty()),
}
}
struct NthIterator {
input: PipelineIterator,
rows: Vec<usize>,
skip: bool,
current: usize,
}
impl Iterator for NthIterator {
type Item = Value;
fn next(&mut self) -> Option<Self::Item> {
loop {
if !self.skip {
if let Some(row) = self.rows.first() {
if self.current == *row {
self.rows.remove(0);
self.current += 1;
return self.input.next();
} else {
self.current += 1;
let _ = self.input.next();
continue;
}
} else {
return None;
}
} else if let Some(row) = self.rows.first() {
if self.current == *row {
self.rows.remove(0);
self.current += 1;
let _ = self.input.next();
continue;
} else {
self.current += 1;
return self.input.next();
}
} else {
return self.input.next();
}
}
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_examples() {
use crate::test_examples;
test_examples(Select)
}
}