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'Fill match arms' should work with existing match arms #3623

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Merged
merged 3 commits into from
Mar 20, 2020
Merged

'Fill match arms' should work with existing match arms #3623

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6087c01
'Fill match arms' should work with existing match arms
slyngbaek Mar 17, 2020
5f8f8a3
Don't show assist if all arms are present
slyngbaek Mar 17, 2020
b5ba9c3
Address nits and suggestions.
slyngbaek Mar 17, 2020
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202 changes: 177 additions & 25 deletions crates/ra_assists/src/handlers/fill_match_arms.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -4,9 +4,11 @@ use std::iter;

use hir::{Adt, HasSource, Semantics};
use ra_ide_db::RootDatabase;
use ra_syntax::ast::{self, edit::IndentLevel, make, AstNode, NameOwner};

use crate::{Assist, AssistCtx, AssistId};
use ra_syntax::ast::{self, edit::IndentLevel, make, AstNode, NameOwner};

use ast::{MatchArm, Pat};

// Assist: fill_match_arms
//
Expand Down Expand Up @@ -36,16 +38,6 @@ pub(crate) fn fill_match_arms(ctx: AssistCtx) -> Option<Assist> {
let match_expr = ctx.find_node_at_offset::<ast::MatchExpr>()?;
let match_arm_list = match_expr.match_arm_list()?;

// We already have some match arms, so we don't provide any assists.
// Unless if there is only one trivial match arm possibly created
// by match postfix complete. Trivial match arm is the catch all arm.
let mut existing_arms = match_arm_list.arms();
if let Some(arm) = existing_arms.next() {
if !is_trivial(&arm) || existing_arms.next().is_some() {
return None;
}
};

let expr = match_expr.expr()?;
let enum_def = resolve_enum_def(&ctx.sema, &expr)?;
let module = ctx.sema.scope(expr.syntax()).module()?;
Expand All @@ -55,30 +47,54 @@ pub(crate) fn fill_match_arms(ctx: AssistCtx) -> Option<Assist> {
return None;
}

let mut arms: Vec<MatchArm> = match_arm_list.arms().collect();
if arms.len() == 1 {
if let Some(Pat::PlaceholderPat(..)) = arms[0].pat() {
arms.clear();
}
}

let db = ctx.db;
let missing_arms: Vec<MatchArm> = variants
.into_iter()
.filter_map(|variant| build_pat(db, module, variant))
.filter(|variant_pat| is_variant_missing(&mut arms, variant_pat))
.map(|pat| make::match_arm(iter::once(pat), make::expr_unit()))
.collect();

if missing_arms.is_empty() {
return None;
}

ctx.add_assist(AssistId("fill_match_arms"), "Fill match arms", |edit| {
let indent_level = IndentLevel::from_node(match_arm_list.syntax());
arms.extend(missing_arms);

let new_arm_list = {
let arms = variants
.into_iter()
.filter_map(|variant| build_pat(db, module, variant))
.map(|pat| make::match_arm(iter::once(pat), make::expr_unit()));
indent_level.increase_indent(make::match_arm_list(arms))
};
let indent_level = IndentLevel::from_node(match_arm_list.syntax());
let new_arm_list = indent_level.increase_indent(make::match_arm_list(arms));

edit.target(match_expr.syntax().text_range());
edit.set_cursor(expr.syntax().text_range().start());
edit.replace_ast(match_arm_list, new_arm_list);
})
}

fn is_trivial(arm: &ast::MatchArm) -> bool {
match arm.pat() {
Some(ast::Pat::PlaceholderPat(..)) => true,
_ => false,
}
fn is_variant_missing(existing_arms: &mut Vec<MatchArm>, var: &Pat) -> bool {
existing_arms.iter().filter_map(|arm| arm.pat()).all(|pat| {
// Special casee OrPat as separate top-level pats
let top_level_pats: Vec<Pat> = match pat {
Pat::OrPat(pats) => pats.pats().collect::<Vec<_>>(),
_ => vec![pat],
};

!top_level_pats.iter().any(|pat| does_pat_match_variant(pat, var))
})
}

fn does_pat_match_variant(pat: &Pat, var: &Pat) -> bool {
let pat_head = pat.syntax().first_child().map(|node| node.text());
let var_head = var.syntax().first_child().map(|node| node.text());

pat_head == var_head
}

fn resolve_enum_def(sema: &Semantics<RootDatabase>, expr: &ast::Expr) -> Option<hir::Enum> {
Expand Down Expand Up @@ -110,10 +126,146 @@ fn build_pat(db: &RootDatabase, module: hir::Module, var: hir::EnumVariant) -> O

#[cfg(test)]
mod tests {
use crate::helpers::{check_assist, check_assist_target};
use crate::helpers::{check_assist, check_assist_not_applicable, check_assist_target};

use super::fill_match_arms;

#[test]
fn all_match_arms_provided() {
check_assist_not_applicable(
fill_match_arms,
r#"
enum A {
As,
Bs{x:i32, y:Option<i32>},
Cs(i32, Option<i32>),
}
fn main() {
match A::As<|> {
A::As,
A::Bs{x,y:Some(_)} => (),
A::Cs(_, Some(_)) => (),
}
}
"#,
);
}

#[test]
fn partial_fill_record_tuple() {
check_assist(
fill_match_arms,
r#"
enum A {
As,
Bs{x:i32, y:Option<i32>},
Cs(i32, Option<i32>),
}
fn main() {
match A::As<|> {
A::Bs{x,y:Some(_)} => (),
A::Cs(_, Some(_)) => (),
}
}
"#,
r#"
enum A {
As,
Bs{x:i32, y:Option<i32>},
Cs(i32, Option<i32>),
}
fn main() {
match <|>A::As {
A::Bs{x,y:Some(_)} => (),
A::Cs(_, Some(_)) => (),
A::As => (),
}
}
"#,
);
}

#[test]
fn partial_fill_or_pat() {
check_assist(
fill_match_arms,
r#"
enum A {
As,
Bs,
Cs(Option<i32>),
}
fn main() {
match A::As<|> {
A::Cs(_) | A::Bs => (),
}
}
"#,
r#"
enum A {
As,
Bs,
Cs(Option<i32>),
}
fn main() {
match <|>A::As {
A::Cs(_) | A::Bs => (),
A::As => (),
}
}
"#,
);
}

#[test]
fn partial_fill() {
check_assist(
fill_match_arms,
r#"
enum A {
As,
Bs,
Cs,
Ds(String),
Es(B),
}
enum B {
Xs,
Ys,
}
fn main() {
match A::As<|> {
A::Bs if 0 < 1 => (),
A::Ds(_value) => (),
A::Es(B::Xs) => (),
}
}
"#,
r#"
enum A {
As,
Bs,
Cs,
Ds(String),
Es(B),
}
enum B {
Xs,
Ys,
}
fn main() {
match <|>A::As {
A::Bs if 0 < 1 => (),
A::Ds(_value) => (),
A::Es(B::Xs) => (),
A::As => (),
A::Cs => (),
}
}
"#,
);
}

#[test]
fn fill_match_arms_empty_body() {
check_assist(
Expand Down