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use indexmap::IndexMap;
use nu_engine::command_prelude::*;
use nu_protocol::ast::PathMember;
#[derive(Clone)]
pub struct Flatten;
impl Command for Flatten {
fn name(&self) -> &str {
"flatten"
}
fn signature(&self) -> Signature {
Signature::build("flatten")
.input_output_types(vec![
(
Type::List(Box::new(Type::Any)),
Type::List(Box::new(Type::Any)),
),
(Type::record(), Type::table()),
])
.rest(
"rest",
SyntaxShape::String,
"Optionally flatten data by column.",
)
.switch("all", "flatten inner table one level out", Some('a'))
.category(Category::Filters)
}
fn description(&self) -> &str {
"Flatten the table."
}
fn run(
&self,
engine_state: &EngineState,
stack: &mut Stack,
call: &Call,
input: PipelineData,
) -> Result<PipelineData, ShellError> {
flatten(engine_state, stack, call, input)
}
fn examples(&self) -> Vec<Example> {
vec![
Example {
description: "flatten a table",
example: "[[N, u, s, h, e, l, l]] | flatten ",
result: Some(Value::test_list(vec![
Value::test_string("N"),
Value::test_string("u"),
Value::test_string("s"),
Value::test_string("h"),
Value::test_string("e"),
Value::test_string("l"),
Value::test_string("l"),
])),
},
Example {
description: "flatten a table, get the first item",
example: "[[N, u, s, h, e, l, l]] | flatten | first",
result: None, //Some(Value::test_string("N")),
},
Example {
description: "flatten a column having a nested table",
example: "[[origin, people]; [Ecuador, ([[name, meal]; ['Andres', 'arepa']])]] | flatten --all | get meal",
result: None, //Some(Value::test_string("arepa")),
},
Example {
description: "restrict the flattening by passing column names",
example: "[[origin, crate, versions]; [World, ([[name]; ['nu-cli']]), ['0.21', '0.22']]] | flatten versions --all | last | get versions",
result: None, //Some(Value::test_string("0.22")),
},
Example {
description: "Flatten inner table",
example: "{ a: b, d: [ 1 2 3 4 ], e: [ 4 3 ] } | flatten d --all",
result: Some(Value::list(
vec![
Value::test_record(record! {
"a" => Value::test_string("b"),
"d" => Value::test_int(1),
"e" => Value::test_list(
vec![Value::test_int(4), Value::test_int(3)],
),
}),
Value::test_record(record! {
"a" => Value::test_string("b"),
"d" => Value::test_int(2),
"e" => Value::test_list(
vec![Value::test_int(4), Value::test_int(3)],
),
}),
Value::test_record(record! {
"a" => Value::test_string("b"),
"d" => Value::test_int(3),
"e" => Value::test_list(
vec![Value::test_int(4), Value::test_int(3)],
),
}),
Value::test_record(record! {
"a" => Value::test_string("b"),
"d" => Value::test_int(4),
"e" => Value::test_list(
vec![Value::test_int(4), Value::test_int(3)],
)
}),
],
Span::test_data(),
)),
},
]
}
}
fn flatten(
engine_state: &EngineState,
stack: &mut Stack,
call: &Call,
input: PipelineData,
) -> Result<PipelineData, ShellError> {
let columns: Vec<CellPath> = call.rest(engine_state, stack, 0)?;
let metadata = input.metadata();
let flatten_all = call.has_flag(engine_state, stack, "all")?;
input
.flat_map(
move |item| flat_value(&columns, item, flatten_all),
engine_state.signals(),
)
.map(|x| x.set_metadata(metadata))
}
enum TableInside {
// handle for a column which contains a single list(but not list of records)
// it contains (column, span, values in the column, column index).
Entries(String, Vec<Value>, usize),
// handle for a column which contains a table, we can flatten the inner column to outer level
// `records` is the nested/inner table to flatten to the outer level
// `parent_column_name` is handled for conflicting column name, the nested table may contains columns which has the same name
// to outer level, for that case, the output column name should be f"{parent_column_name}_{inner_column_name}".
// `parent_column_index` is the column index in original table.
FlattenedRows {
records: Vec<Record>,
parent_column_name: String,
parent_column_index: usize,
},
}
fn flat_value(columns: &[CellPath], item: Value, all: bool) -> Vec<Value> {
let tag = item.span();
match item {
Value::Record { val, .. } => {
let mut out = IndexMap::<String, Value>::new();
let mut inner_table = None;
for (column_index, (column, value)) in val.into_owned().into_iter().enumerate() {
let column_requested = columns.iter().find(|c| c.to_column_name() == column);
let need_flatten = { columns.is_empty() || column_requested.is_some() };
let span = value.span();
match value {
Value::Record { ref val, .. } => {
if need_flatten {
for (col, val) in val.clone().into_owned() {
if out.contains_key(&col) {
out.insert(format!("{column}_{col}"), val);
} else {
out.insert(col, val);
}
}
} else if out.contains_key(&column) {
out.insert(format!("{column}_{column}"), value);
} else {
out.insert(column, value);
}
}
Value::List { vals, .. } => {
if need_flatten && inner_table.is_some() {
return vec![Value::error(
ShellError::UnsupportedInput {
msg: "can only flatten one inner list at a time. tried flattening more than one column with inner lists... but is flattened already".into(),
input: "value originates from here".into(),
msg_span: tag,
input_span: span
},
span,
)];
}
if all && vals.iter().all(|f| f.as_record().is_ok()) {
// it's a table (a list of record, we can flatten inner record)
if need_flatten {
let records = vals
.into_iter()
.filter_map(|v| v.into_record().ok())
.collect();
inner_table = Some(TableInside::FlattenedRows {
records,
parent_column_name: column,
parent_column_index: column_index,
});
} else if out.contains_key(&column) {
out.insert(format!("{column}_{column}"), Value::list(vals, span));
} else {
out.insert(column, Value::list(vals, span));
}
} else if !columns.is_empty() {
let cell_path =
column_requested.and_then(|x| match x.members.first() {
Some(PathMember::String { val, .. }) => Some(val),
_ => None,
});
if let Some(r) = cell_path {
inner_table =
Some(TableInside::Entries(r.clone(), vals, column_index));
} else {
out.insert(column, Value::list(vals, span));
}
} else {
inner_table = Some(TableInside::Entries(column, vals, column_index));
}
}
_ => {
out.insert(column, value);
}
}
}
let mut expanded = vec![];
match inner_table {
Some(TableInside::Entries(column, entries, parent_column_index)) => {
for entry in entries {
let base = out.clone();
let mut record = Record::new();
let mut index = 0;
for (col, val) in base.into_iter() {
// meet the flattened column, push them to result record first
// this can avoid output column order changed.
if index == parent_column_index {
record.push(column.clone(), entry.clone());
}
record.push(col, val);
index += 1;
}
// the flattened column may be the last column in the original table.
if index == parent_column_index {
record.push(column.clone(), entry);
}
expanded.push(Value::record(record, tag));
}
}
Some(TableInside::FlattenedRows {
records,
parent_column_name,
parent_column_index,
}) => {
for inner_record in records {
let base = out.clone();
let mut record = Record::new();
let mut index = 0;
for (base_col, base_val) in base {
// meet the flattened column, push them to result record first
// this can avoid output column order changed.
if index == parent_column_index {
for (col, val) in &inner_record {
if record.contains(col) {
record.push(
format!("{parent_column_name}_{col}"),
val.clone(),
);
} else {
record.push(col, val.clone());
};
}
}
record.push(base_col, base_val);
index += 1;
}
// the flattened column may be the last column in the original table.
if index == parent_column_index {
for (col, val) in inner_record {
if record.contains(&col) {
record.push(format!("{parent_column_name}_{col}"), val);
} else {
record.push(col, val);
}
}
}
expanded.push(Value::record(record, tag));
}
}
None => {
expanded.push(Value::record(out.into_iter().collect(), tag));
}
}
expanded
}
Value::List { vals, .. } => vals,
item => vec![item],
}
}
#[cfg(test)]
mod test {
use super::*;
#[test]
fn test_examples() {
use crate::test_examples;
test_examples(Flatten {})
}
}