forked from extern/nushell
Add pattern matching (#8590)
# Description
This adds `match` and basic pattern matching.
An example:
```
match $x {
1..10 => { print "Value is between 1 and 10" }
{ foo: $bar } => { print $"Value has a 'foo' field with value ($bar)" }
[$a, $b] => { print $"Value is a list with two items: ($a) and ($b)" }
_ => { print "Value is none of the above" }
}
```
Like the recent changes to `if` to allow it to be used as an expression,
`match` can also be used as an expression. This allows you to assign the
result to a variable, eg) `let xyz = match ...`
I've also included a short-hand pattern for matching records, as I think
it might help when doing a lot of record patterns: `{$foo}` which is
equivalent to `{foo: $foo}`.
There are still missing components, so consider this the first step in
full pattern matching support. Currently missing:
* Patterns for strings
* Or-patterns (like the `|` in Rust)
* Patterns for tables (unclear how we want to match a table, so it'll
need some design)
* Patterns for binary values
* And much more
# User-Facing Changes
[see above]
# Tests + Formatting
Don't forget to add tests that cover your changes.
Make sure you've run and fixed any issues with these commands:
- `cargo fmt --all -- --check` to check standard code formatting (`cargo
fmt --all` applies these changes)
- `cargo clippy --workspace -- -D warnings -D clippy::unwrap_used -A
clippy::needless_collect` to check that you're using the standard code
style
- `cargo test --workspace` to check that all tests pass
> **Note**
> from `nushell` you can also use the `toolkit` as follows
> ```bash
> use toolkit.nu # or use an `env_change` hook to activate it
automatically
> toolkit check pr
> ```
# After Submitting
If your PR had any user-facing changes, update [the
documentation](https://github.com/nushell/nushell.github.io) after the
PR is merged, if necessary. This will help us keep the docs up to date.
This commit is contained in:
JT
GitHub
201
crates/nu-protocol/src/engine/pattern_match.rs
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201
crates/nu-protocol/src/engine/pattern_match.rs
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@ -0,0 +1,201 @@
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use crate::{
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ast::{Expr, MatchPattern, Pattern, RangeInclusion},
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Unit, Value, VarId,
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};
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pub trait Matcher {
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fn match_value(&self, value: &Value, matches: &mut Vec<(VarId, Value)>) -> bool;
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}
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impl Matcher for MatchPattern {
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fn match_value(&self, value: &Value, matches: &mut Vec<(VarId, Value)>) -> bool {
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self.pattern.match_value(value, matches)
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}
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}
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impl Matcher for Pattern {
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fn match_value(&self, value: &Value, matches: &mut Vec<(VarId, Value)>) -> bool {
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match self {
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Pattern::Garbage => false,
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Pattern::IgnoreValue => true,
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Pattern::Record(field_patterns) => match value {
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Value::Record { cols, vals, .. } => {
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'top: for field_pattern in field_patterns {
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for (col_idx, col) in cols.iter().enumerate() {
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if col == &field_pattern.0 {
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// We have found the field
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let result = field_pattern.1.match_value(&vals[col_idx], matches);
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if !result {
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return false;
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} else {
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continue 'top;
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}
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}
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}
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return false;
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}
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true
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}
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_ => false,
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},
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Pattern::Variable(var_id) => {
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// TODO: FIXME: This needs the span of this variable
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matches.push((*var_id, value.clone()));
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true
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}
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Pattern::List(items) => match &value {
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Value::List { vals, .. } => {
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if items.len() > vals.len() {
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// We need more items in our pattern than are available in the Value
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return false;
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}
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for (val_idx, val) in vals.iter().enumerate() {
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// We require that the pattern and the value have the same number of items, or the pattern does not match
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// The only exception is if the pattern includes a `..` pattern
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if let Some(pattern) = items.get(val_idx) {
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if !pattern.match_value(val, matches) {
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return false;
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}
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} else {
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return false;
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}
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}
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true
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}
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_ => false,
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},
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Pattern::Value(pattern_value) => {
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// TODO: Fill this out with the rest of them
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match &pattern_value.expr {
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Expr::Int(x) => {
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if let Value::Int { val, .. } = &value {
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x == val
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} else {
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false
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}
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}
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Expr::Binary(x) => {
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if let Value::Binary { val, .. } = &value {
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x == val
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} else {
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false
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}
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}
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Expr::Bool(x) => {
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if let Value::Bool { val, .. } = &value {
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x == val
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} else {
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false
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}
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}
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Expr::ValueWithUnit(amount, unit) => {
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if let Value::Filesize { val, .. } = &value {
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// FIXME: we probably want this math in one place that both the
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// pattern matcher and the eval engine can get to it
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match &amount.expr {
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Expr::Int(amount) => match &unit.item {
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Unit::Byte => amount == val,
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Unit::Kilobyte => *val == amount * 1000,
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Unit::Megabyte => *val == amount * 1000 * 1000,
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Unit::Gigabyte => *val == amount * 1000 * 1000 * 1000,
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Unit::Petabyte => *val == amount * 1000 * 1000 * 1000 * 1000,
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Unit::Exabyte => {
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*val == amount * 1000 * 1000 * 1000 * 1000 * 1000
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}
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Unit::Zettabyte => {
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*val == amount * 1000 * 1000 * 1000 * 1000 * 1000 * 1000
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}
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Unit::Kibibyte => *val == amount * 1024,
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Unit::Mebibyte => *val == amount * 1024 * 1024,
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Unit::Gibibyte => *val == amount * 1024 * 1024 * 1024,
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Unit::Pebibyte => *val == amount * 1024 * 1024 * 1024 * 1024,
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Unit::Exbibyte => {
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*val == amount * 1024 * 1024 * 1024 * 1024 * 1024
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}
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Unit::Zebibyte => {
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*val == amount * 1024 * 1024 * 1024 * 1024 * 1024 * 1024
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}
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_ => false,
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},
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_ => false,
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}
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} else if let Value::Duration { val, .. } = &value {
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// FIXME: we probably want this math in one place that both the
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// pattern matcher and the eval engine can get to it
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match &amount.expr {
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Expr::Int(amount) => match &unit.item {
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Unit::Nanosecond => val == amount,
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Unit::Microsecond => *val == amount * 1000,
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Unit::Millisecond => *val == amount * 1000 * 1000,
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Unit::Second => *val == amount * 1000 * 1000 * 1000,
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Unit::Minute => *val == amount * 1000 * 1000 * 1000 * 60,
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Unit::Hour => *val == amount * 1000 * 1000 * 1000 * 60 * 60,
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Unit::Day => *val == amount * 1000 * 1000 * 1000 * 60 * 60 * 24,
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Unit::Week => {
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*val == amount * 1000 * 1000 * 1000 * 60 * 60 * 24 * 7
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}
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_ => false,
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},
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_ => false,
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}
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} else {
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false
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}
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}
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Expr::Range(start, step, end, inclusion) => {
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// TODO: Add support for floats
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let start = if let Some(start) = &start {
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match &start.expr {
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Expr::Int(start) => *start,
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_ => return false,
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}
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} else {
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0
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};
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let end = if let Some(end) = &end {
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match &end.expr {
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Expr::Int(end) => *end,
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_ => return false,
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}
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} else {
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i64::MAX
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};
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let step = if let Some(step) = step {
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match &step.expr {
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Expr::Int(step) => *step - start,
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_ => return false,
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}
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} else if end < start {
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-1
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} else {
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1
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};
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let (start, end) = if end < start {
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(end, start)
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} else {
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(start, end)
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};
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if let Value::Int { val, .. } = &value {
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if matches!(inclusion.inclusion, RangeInclusion::RightExclusive) {
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*val >= start && *val < end && ((*val - start) % step) == 0
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} else {
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*val >= start && *val <= end && ((*val - start) % step) == 0
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}
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} else {
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false
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}
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}
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_ => false,
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}
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}
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}
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}
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}
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