rust/crates/ide_assists/src/handlers/destructure_tuple_binding.rs

use ide_db::{
    assists::{AssistId, AssistKind},
    defs::Definition,
    search::{FileReference, SearchScope, UsageSearchResult},
};
use itertools::Itertools;
use syntax::{
    ast::{self, AstNode, FieldExpr, IdentPat, NameOwner},
    SyntaxNode, TextRange,
};

use crate::assist_context::{AssistBuilder, AssistContext, Assists};

// Assist: destructure_tuple_binding
//
// Destructures a tuple binding into its items.
//
// ```
// fn main() {
//     let $0t = (1,2);
//     let v = t.0;
// }
// ```
// ->
// ```
// fn main() {
//     let (_0, _1) = (1,2);
//     let v = _0;
// }
// ```

pub(crate) fn destructure_tuple_binding(acc: &mut Assists, ctx: &AssistContext) -> Option<()> {
    // find variable pattern under cursor
    let ident_pat = ctx.find_node_at_offset::<ast::IdentPat>()?;
    let data = collect_data(ident_pat, ctx)?;

    acc.add(
        AssistId("destructure_tuple", AssistKind::RefactorRewrite),
        "Destructure tuple",
        data.range,
        |builder| {
            edit_tuple_assignment(&data, builder, ctx);
            edit_tuple_usages(&data, builder, ctx);
        },
    );

    Some(())
}

fn collect_data(ident_pat: IdentPat, ctx: &AssistContext) -> Option<TupleData> {
    if ident_pat.at_token().is_some() {
        // cannot destructure pattern with sub-pattern:
        // Only IdentPat can have sub-pattern,
        // but not TuplePat (`(a,b)`)
        cov_mark::hit!(destructure_tuple_subpattern);
        return None;
    }

    let ty = ctx.sema.type_of_pat(&ident_pat.clone().into())?;
    // might be reference
    let ty = ty.strip_references();
    // must be tuple
    let field_types = ty.tuple_fields(ctx.db());
    if field_types.is_empty() {
        cov_mark::hit!(destructure_tuple_no_tuple);
        return None;
    }

    let name = ident_pat.name()?.to_string();
    let range = ident_pat.syntax().text_range();

    let usages = ctx.sema.to_def(&ident_pat).map(|def| {
        Definition::Local(def)
            .usages(&ctx.sema)
            .in_scope(SearchScope::single_file(ctx.frange.file_id))
            .all()
    });

    let field_names = (0..field_types.len())
        .map(|i| generate_name(i, &name, &ident_pat, &usages, ctx))
        .collect_vec();

    Some(TupleData { range, field_names, usages })
}

fn generate_name(
    index: usize,
    _tuple_name: &str,
    _ident_pat: &IdentPat,
    _usages: &Option<UsageSearchResult>,
    _ctx: &AssistContext,
) -> String {
    //TODO: detect if name already used
    format!("_{}", index)
}

struct TupleData {
    // ident_pat: IdentPat,
    // name: String,
    range: TextRange,
    field_names: Vec<String>,
    // field_types: Vec<Type>,
    usages: Option<UsageSearchResult>,
}
fn edit_tuple_assignment(data: &TupleData, builder: &mut AssistBuilder, ctx: &AssistContext) {
    let new_tuple = {
        let fields = data
            .field_names
            .iter()
            .map(|name| ast::Pat::from(ast::make::ident_pat(false, false, ast::make::name(name))));
        ast::make::tuple_pat(fields)
    };

    match ctx.config.snippet_cap {
        Some(cap) => {
            // No support for placeholders in Code Actions, except for special rust analyzer handling which supports only first `$0`
            //  -> place cursor on first variable
            let mut snip = new_tuple.to_string();
            snip.insert_str(1, "$0");
            builder.replace_snippet(cap, data.range, snip);
        }
        None => builder.replace(data.range, new_tuple.to_string()),
    };
}

fn edit_tuple_usages(
    data: &TupleData,
    builder: &mut AssistBuilder,
    ctx: &AssistContext,
) {
    if let Some(usages) = data.usages.as_ref() {
        for (file_id, refs) in usages.iter() {
            builder.edit_file(*file_id);
    
            for r in refs {
                edit_tuple_usage(r, data, builder, ctx);
            }
        }
    }
}
fn edit_tuple_usage(
    usage: &FileReference,
    data: &TupleData,
    builder: &mut AssistBuilder,
    _ctx: &AssistContext,
) {
    match detect_tuple_index(usage.name.syntax(), data) {
        Some((expr, idx)) => {
            // index field access
            let text = &data.field_names[idx];
            let range = expr.syntax().text_range();
            builder.replace(range, text);
        }
        None => {
            // no index access -> make invalid -> requires handling by user
            // -> put usage in block comment
            builder.insert(usage.range.start(), "/*");
            builder.insert(usage.range.end(), "*/");
        }
    }
}

fn detect_tuple_index(usage: &SyntaxNode, data: &TupleData) -> Option<(FieldExpr, usize)> {
    // usage is IDENT
    // IDENT
    //  NAME_REF
    //   PATH_SEGMENT
    //    PATH
    //     PATH_EXPR
    //      PAREN_EXRP*
    //       FIELD_EXPR
    let node = usage
        .ancestors()
        .skip_while(|s| !ast::PathExpr::can_cast(s.kind()))
        .skip(1) // PATH_EXPR
        .find(|s| !ast::ParenExpr::can_cast(s.kind()))?;    // skip parentheses

    if let Some(field_expr) = ast::FieldExpr::cast(node) {
        let idx = field_expr.name_ref()?.as_tuple_field()?;
        if idx < data.field_names.len() {
            Some((field_expr, idx))
        } else {
            // tuple index out of range
            None
        }
    } else {
        None
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    use crate::tests::{check_assist, check_assist_not_applicable};

    #[test]
    fn dont_trigger_on_unit() {
        cov_mark::check!(destructure_tuple_no_tuple);
        check_assist_not_applicable(
            destructure_tuple_binding,
            r#"
fn main() {
let $0v = ();
}
            "#,
        )
    }
    #[test]
    fn dont_trigger_on_number() {
        cov_mark::check!(destructure_tuple_no_tuple);
        check_assist_not_applicable(
            destructure_tuple_binding,
            r#"
fn main() {
let $0v = 32;
}
            "#,
        )
    }

    #[test]
    fn destructure_3_tuple() {
        check_assist(
            destructure_tuple_binding,
            r#"
fn main() {
    let $0tup = (1,2,3);
}
            "#,
            r#"
fn main() {
    let ($0_0, _1, _2) = (1,2,3);
}
            "#,
        )
    }
    #[test]
    fn destructure_2_tuple() {
        check_assist(
            destructure_tuple_binding,
            r#"
fn main() {
    let $0tup = (1,2);
}
            "#,
            r#"
fn main() {
    let ($0_0, _1) = (1,2);
}
            "#,
        )
    }
    #[test]
    fn replace_indices() {
        check_assist(
            destructure_tuple_binding,
            r#"
fn main() {
    let $0tup = (1,2,3);
    let v1 = tup.0;
    let v2 = tup.1;
    let v3 = tup.2;
}
            "#,
            r#"
fn main() {
    let ($0_0, _1, _2) = (1,2,3);
    let v1 = _0;
    let v2 = _1;
    let v3 = _2;
}
            "#,
        )
    }

    #[test]
    fn replace_usage_in_parentheses() {
        check_assist(
            destructure_tuple_binding,
            r#"
fn main() {
    let $0tup = (1,2,3);
    let a = (tup).1;
    let b = ((tup)).1;
}
            "#,
            r#"
fn main() {
    let ($0_0, _1, _2) = (1,2,3);
    let a = _1;
    let b = _1;
}
            "#,
        )
    }

    #[test]
    fn handle_function_call() {
        check_assist(
            destructure_tuple_binding,
            r#"
fn main() {
    let $0tup = (1,2);
    let v = tup.into();
}
            "#,
            r#"
fn main() {
    let ($0_0, _1) = (1,2);
    let v = /*tup*/.into();
}
            "#,
        )
    }

    #[test]
    fn handle_invalid_index() {
        check_assist(
            destructure_tuple_binding,
            r#"
fn main() {
    let $0tup = (1,2);
    let v = tup.3;
}
            "#,
            r#"
fn main() {
    let ($0_0, _1) = (1,2);
    let v = /*tup*/.3;
}
            "#,
        )
    }

    #[test]
    fn dont_replace_variable_with_same_name_as_tuple() {
        check_assist(
            destructure_tuple_binding,
            r#"
fn main() {
    let tup = (1,2);
    let v = tup.1;
    let $0tup = (1,2,3);
    let v = tup.1;
    let tup = (1,2,3);
    let v = tup.1;
}
            "#,
            r#"
fn main() {
    let tup = (1,2);
    let v = tup.1;
    let ($0_0, _1, _2) = (1,2,3);
    let v = _1;
    let tup = (1,2,3);
    let v = tup.1;
}
            "#,
        )
    }

    #[test]
    fn keep_function_call_in_tuple_item() {
        check_assist(
            destructure_tuple_binding,
            r#"
fn main() {
    let $0t = ("3.14", 0);
    let pi: f32 = t.0.parse().unwrap();
}
            "#,
            r#"
fn main() {
    let ($0_0, _1) = ("3.14", 0);
    let pi: f32 = _0.parse().unwrap();
}
            "#,
        )
    }

    #[test]
    fn keep_type() {
        check_assist(
            destructure_tuple_binding,
            r#"
fn main() {
    let $0t: (usize, i32) = (1,2);
}
            "#,
            r#"
fn main() {
    let ($0_0, _1): (usize, i32) = (1,2);
}
            "#,
        )
    }

    #[test]
    fn destructure_reference() {
        //Note: `v` has different types:
        // * in 1st: `i32`
        // * in 2nd: `&i32`
        check_assist(
            destructure_tuple_binding,
            r#"
fn main() {
    let t = (1,2);
    let $0t = &t;
    let v = t.0;
}
            "#,
            r#"
fn main() {
    let t = (1,2);
    let ($0_0, _1) = &t;
    let v = _0;
}
            "#,
        )
    }

    #[test]
    fn destructure_multiple_reference() {
        check_assist(
            destructure_tuple_binding,
            r#"
fn main() {
    let t = (1,2);
    let $0t = &&t;
    let v = t.0;
}
            "#,
            r#"
fn main() {
    let t = (1,2);
    let ($0_0, _1) = &&t;
    let v = _0;
}
            "#,
        )
    }

    #[test]
    fn keep_reference() {
        check_assist(
            destructure_tuple_binding,
            r#"
fn foo(t: &(usize, usize)) -> usize {
    match t {
        &$0t => t.0
    }
}
            "#,
            r#"
fn foo(t: &(usize, usize)) -> usize {
    match t {
        &($0_0, _1) => _0
    }
}
            "#,
        )
    }

    #[test]
    fn dont_trigger_for_non_tuple_reference() {
        check_assist_not_applicable(
            destructure_tuple_binding,
            r#"
fn main() {
    let v = 42;
    let $0v = &42;
}
            "#,
        )
    }

    #[test]
    fn dont_trigger_on_static_tuple() {
        check_assist_not_applicable(
            destructure_tuple_binding,
            r#"
static $0TUP: (usize, usize) = (1,2);
            "#,
        )
    }

    #[test]
    fn dont_trigger_on_wildcard() {
        check_assist_not_applicable(
            destructure_tuple_binding,
            r#"
fn main() {
    let $0_ = (1,2);
}
            "#,
        )
    }

    #[test]
    fn dont_trigger_in_struct() {
        check_assist_not_applicable(
            destructure_tuple_binding,
            r#"
struct S {
    $0tup: (usize, usize),
}
            "#,
        )
    }

    #[test]
    fn dont_trigger_in_struct_creation() {
        check_assist_not_applicable(
            destructure_tuple_binding,
            r#"
struct S {
    tup: (usize, usize),
}
fn main() {
    let s = S {
        $0tup: (1,2),
    };
}
            "#,
        )
    }

    #[test]
    fn dont_trigger_on_tuple_struct() {
        check_assist_not_applicable(
            destructure_tuple_binding,
            r#"
struct S(usize, usize);
fn main() {
    let $0s = S(1,2);
}
            "#,
        )
    }

    #[test]
    fn dont_trigger_when_subpattern_exists() {
        // sub-pattern is only allowed with IdentPat (name), not other patterns (like TuplePat)
        cov_mark::check!(destructure_tuple_subpattern);
        check_assist_not_applicable(
            destructure_tuple_binding,
            r#"
fn sum(t: (usize, usize)) -> usize {
    match t {
        $0t @ (1..=3,1..=3) => t.0 + t.1,
        _ => 0,
    }
}
            "#,
        )
    }

    #[test]
    fn in_subpattern() {
        check_assist(
            destructure_tuple_binding,
            r#"
fn main() {
    let t1 @ (_, $0t2) = (1, (2,3));
    let v = t1.0 + t2.0 + t2.1;
}
            "#,
            r#"
fn main() {
    let t1 @ (_, ($0_0, _1)) = (1, (2,3));
    let v = t1.0 + _0 + _1;
}
            "#,
        )
    }

    #[test]
    fn in_nested_tuple() {
        check_assist(
            destructure_tuple_binding,
            r#"
fn main() {
    let ($0tup, v) = ((1,2),3);
}
            "#,
            r#"
fn main() {
    let (($0_0, _1), v) = ((1,2),3);
}
            "#,
        )
    }

    #[test]
    fn in_closure() {
        check_assist(
            destructure_tuple_binding,
            r#"
fn main() {
    let $0tup = (1,2,3);
    let f = |v| v + tup.1;
}
            "#,
            r#"
fn main() {
    let ($0_0, _1, _2) = (1,2,3);
    let f = |v| v + _1;
}
            "#,
        )
    }

    #[test]
    fn in_closure_args() {
        check_assist(
            destructure_tuple_binding,
            r#"
fn main() {
    let f = |$0t| t.0 + t.1;
    let v = f((1,2));
}
            "#,
            r#"
fn main() {
    let f = |($0_0, _1)| _0 + _1;
    let v = f((1,2));
}
            "#,
        )
    }

    #[test]
    fn in_function_args() {
        check_assist(
            destructure_tuple_binding,
            r#"
fn f($0t: (usize, usize)) {
    let v = t.0;
}
            "#,
            r#"
fn f(($0_0, _1): (usize, usize)) {
    let v = _0;
}
            "#,
        )
    }

    #[test]
    fn in_if_let() {
        check_assist(
            destructure_tuple_binding,
            r#"
fn f(t: (usize, usize)) {
    if let $0t = t {
        let v = t.0;
    }
}
            "#,
            r#"
fn f(t: (usize, usize)) {
    if let ($0_0, _1) = t {
        let v = _0;
    }
}
            "#,
        )
    }
    #[test]
    fn in_if_let_option() {
        check_assist(
            destructure_tuple_binding,
            r#"
//- minicore: option
fn f(o: Option<(usize, usize)>) {
    if let Some($0t) = o {
        let v = t.0;
    }
}
            "#,
            r#"
fn f(o: Option<(usize, usize)>) {
    if let Some(($0_0, _1)) = o {
        let v = _0;
    }
}
            "#,
        )
    }


    #[test]
    fn in_match() {
        check_assist(
            destructure_tuple_binding,
            r#"
fn main() {
    match (1,2) {
        $0t => t.1,
    };
}
            "#,
            r#"
fn main() {
    match (1,2) {
        ($0_0, _1) => _1,
    };
}
            "#,
        )
    }
    #[test]
    fn in_match_option() {
        check_assist(
            destructure_tuple_binding,
            r#"
//- minicore: option
fn main() {
    match Some((1,2)) {
        Some($0t) => t.1,
        _ => 0,
    };
}
            "#,
            r#"
fn main() {
    match Some((1,2)) {
        Some(($0_0, _1)) => _1,
        _ => 0,
    };
}
            "#,
        )
    }

    #[test]
    fn in_for() {
        check_assist(
            destructure_tuple_binding,
            r#"
//- minicore: iterators
fn main() {
    for $0t in core::iter::repeat((1,2))  {
        let v = t.1;
    }
}
            "#,
            r#"
fn main() {
    for ($0_0, _1) in core::iter::repeat((1,2))  {
        let v = _1;
    }
}
            "#,
        )
    }
    #[test]
    fn in_for_nested() {
        check_assist(
            destructure_tuple_binding,
            r#"
//- minicore: iterators
fn main() {
    for (a, $0b) in core::iter::repeat((1,(2,3)))  {
        let v = b.1;
    }
}
            "#,
            r#"
fn main() {
    for (a, ($0_0, _1)) in core::iter::repeat((1,(2,3)))  {
        let v = _1;
    }
}
            "#,
        )
    }

    #[test]
    fn not_applicable_on_tuple_usage() {
        //Improvement: might be reasonable to allow & implement
        check_assist_not_applicable(
            destructure_tuple_binding,
            r#"
fn main() {
    let t = (1,2);
    let v = $0t.0;
}
            "#,
        )
    }

    #[test]
    fn replace_all() {
        check_assist(
            destructure_tuple_binding,
            r#"
fn main() {
    let $0t = (1,2);
    let v = t.1;
    let s = (t.0 + t.1) / 2;
    let f = |v| v + t.0;
    let r = f(t.1);
    let e = t == (9,0);
    let m =
      match t {
        (_,2) if t.0 > 2 => 1,
        _ => 0,
      };
}
            "#,
            r#"
fn main() {
    let ($0_0, _1) = (1,2);
    let v = _1;
    let s = (_0 + _1) / 2;
    let f = |v| v + _0;
    let r = f(_1);
    let e = /*t*/ == (9,0);
    let m =
      match /*t*/ {
        (_,2) if _0 > 2 => 1,
        _ => 0,
      };
}
            "#,
        )
    }

    #[test]
    fn non_trivial_tuple_assignment() {
        check_assist(
            destructure_tuple_binding,
            r#"
fn main {
    let $0t = 
        if 1 > 2 {
            (1,2)
        } else {
            (5,6)
        };
    let v1 = t.0;
    let v2 =
        if t.0 > t.1 {
            t.0 - t.1
        } else {
            t.1 - t.0
        };
}
            "#,
            r#"
fn main {
    let ($0_0, _1) = 
        if 1 > 2 {
            (1,2)
        } else {
            (5,6)
        };
    let v1 = _0;
    let v2 =
        if _0 > _1 {
            _0 - _1
        } else {
            _1 - _0
        };
}
            "#,
        )
    }

    // -----------------------
    #[test]
    #[ignore]
    fn replace_in_macro_call() {
        // doesn't work: cannot find usage in `println!`
        // Note: Just `t` works, but not `t.0`
        check_assist(
            destructure_tuple_binding,
            r#"
fn main() {
    let $0t = (1,2);
    println!("{}", t.0);
}
            "#,
            r#"
fn main() {
    let ($0_0, _1) = (1,2);
    println!("{}", _0);
}
            "#,
        )
    }
}