rust-analyzer/crates/ide_completion/src/completions/attribute/derive.rs

//! Completion for derives
use hir::{HasAttrs, ScopeDef};
use ide_db::SymbolKind;
use itertools::Itertools;
use syntax::SmolStr;

use crate::{
    context::{CompletionContext, PathCompletionCtx, PathKind, PathQualifierCtx},
    item::CompletionItem,
    Completions,
};

pub(crate) fn complete_derive(acc: &mut Completions, ctx: &CompletionContext) {
    let (qualifier, is_absolute_path) = match ctx.path_context {
        Some(PathCompletionCtx {
            kind: Some(PathKind::Derive),
            ref qualifier,
            is_absolute_path,
            ..
        }) => (qualifier, is_absolute_path),
        _ => return,
    };

    let core = ctx.famous_defs().core();

    match qualifier {
        Some(PathQualifierCtx { resolution, is_super_chain, .. }) => {
            if *is_super_chain {
                acc.add_keyword(ctx, "super::");
            }

            let module = match resolution {
                Some(hir::PathResolution::Def(hir::ModuleDef::Module(it))) => it,
                _ => return,
            };

            for (name, def) in module.scope(ctx.db, Some(ctx.module)) {
                let add_def = match def {
                    ScopeDef::ModuleDef(hir::ModuleDef::Macro(mac)) => {
                        !ctx.existing_derives.contains(&mac) && mac.is_derive(ctx.db)
                    }
                    ScopeDef::ModuleDef(hir::ModuleDef::Module(_)) => true,
                    _ => false,
                };
                if add_def {
                    acc.add_resolution(ctx, name, def);
                }
            }
        }
        None if is_absolute_path => acc.add_crate_roots(ctx),
        // only show modules in a fresh UseTree
        None => {
            ctx.process_all_names(&mut |name, def| {
                let mac = match def {
                    ScopeDef::ModuleDef(hir::ModuleDef::Macro(mac))
                        if !ctx.existing_derives.contains(&mac) && mac.is_derive(ctx.db) =>
                    {
                        mac
                    }
                    ScopeDef::ModuleDef(hir::ModuleDef::Module(_)) => {
                        return acc.add_resolution(ctx, name, def);
                    }
                    _ => return,
                };

                match (core, mac.module(ctx.db).krate()) {
                    // show derive dependencies for `core`/`std` derives
                    (Some(core), mac_krate) if core == mac_krate && qualifier.is_none() => {}
                    _ => return acc.add_resolution(ctx, name, def),
                };

                let name_ = name.to_smol_str();
                let find = DEFAULT_DERIVE_DEPENDENCIES
                    .iter()
                    .find(|derive_completion| derive_completion.label == name_);

                match find {
                    Some(derive_completion) => {
                        let mut components = vec![derive_completion.label];
                        components.extend(derive_completion.dependencies.iter().filter(
                            |&&dependency| {
                                !ctx.existing_derives
                                    .iter()
                                    .map(|it| it.name(ctx.db))
                                    .any(|it| it.to_smol_str() == dependency)
                            },
                        ));
                        let lookup = components.join(", ");
                        let label = Itertools::intersperse(components.into_iter().rev(), ", ");

                        let mut item = CompletionItem::new(
                            SymbolKind::Derive,
                            ctx.source_range(),
                            SmolStr::from_iter(label),
                        );
                        if let Some(docs) = mac.docs(ctx.db) {
                            item.documentation(docs);
                        }
                        item.lookup_by(lookup);
                        item.add_to(acc);
                    }
                    None => acc.add_resolution(ctx, name, def),
                }
            });
            acc.add_nameref_keywords_with_colon(ctx);
        }
    }
}

struct DeriveDependencies {
    label: &'static str,
    dependencies: &'static [&'static str],
}

/// Standard Rust derives that have dependencies
/// (the dependencies are needed so that the main derive don't break the compilation when added)
const DEFAULT_DERIVE_DEPENDENCIES: &[DeriveDependencies] = &[
    DeriveDependencies { label: "Copy", dependencies: &["Clone"] },
    DeriveDependencies { label: "Eq", dependencies: &["PartialEq"] },
    DeriveDependencies { label: "Ord", dependencies: &["PartialOrd", "Eq", "PartialEq"] },
    DeriveDependencies { label: "PartialOrd", dependencies: &["PartialEq"] },
];