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8da27a1a09
# Description
This PR creates a new `Record` type to reduce duplicate code and
possibly bugs as well. (This is an edited version of #9648.)
- `Record` implements `FromIterator` and `IntoIterator` and so can be
iterated over or collected into. For example, this helps with
conversions to and from (hash)maps. (Also, no more
`cols.iter().zip(vals)`!)
- `Record` has a `push(col, val)` function to help insure that the
number of columns is equal to the number of values. I caught a few
potential bugs thanks to this (e.g. in the `ls` command).
- Finally, this PR also adds a `record!` macro that helps simplify
record creation. It is used like so:
```rust
record! {
"key1" => some_value,
"key2" => Value::string("text", span),
"key3" => Value::int(optional_int.unwrap_or(0), span),
"key4" => Value::bool(config.setting, span),
}
```
Since macros hinder formatting, etc., the right hand side values should
be relatively short and sweet like the examples above.
Where possible, prefer `record!` or `.collect()` on an iterator instead
of multiple `Record::push`s, since the first two automatically set the
record capacity and do less work overall.
# User-Facing Changes
Besides the changes in `nu-protocol` the only other breaking changes are
to `nu-table::{ExpandedTable::build_map, JustTable::kv_table}`.
30 lines
1.1 KiB
Rust
30 lines
1.1 KiB
Rust
use crate::{Record, ShellError, Span, Value};
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use std::fmt;
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// Trait definition for a lazy record (where columns are evaluated on-demand)
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// typetag is needed to make this implement Serialize+Deserialize... even though we should never actually serialize a LazyRecord.
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// To serialize a LazyRecord, collect it into a Value::Record with collect() first.
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pub trait LazyRecord<'a>: fmt::Debug + Send + Sync {
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// All column names
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fn column_names(&'a self) -> Vec<&'a str>;
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// Get 1 specific column value
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fn get_column_value(&self, column: &str) -> Result<Value, ShellError>;
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fn span(&self) -> Span;
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// Convert the lazy record into a regular Value::Record by collecting all its columns
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fn collect(&'a self) -> Result<Value, ShellError> {
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self.column_names()
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.into_iter()
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.map(|col| {
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let val = self.get_column_value(col)?;
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Ok((col.to_owned(), val))
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})
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.collect::<Result<Record, _>>()
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.map(|record| Value::record(record, self.span()))
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}
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fn clone_value(&self, span: Span) -> Value;
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}
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