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|
//! An algorithm to find a path to refer to a certain item.
use crate::{
db::DefDatabase,
item_scope::ItemInNs,
path::{ModPath, PathKind},
ModuleId, ModuleDefId,
};
use hir_expand::name::Name;
// TODO handle prelude
// TODO handle enum variants
// TODO don't import from super imports? or at least deprioritize
// TODO use super?
// TODO use shortest path
// TODO performance / memoize
pub fn find_path(db: &impl DefDatabase, item: ItemInNs, from: ModuleId) -> Option<ModPath> {
// 1. Find all locations that the item could be imported from (i.e. that are visible)
// - this needs to consider other crates, for reexports from transitive dependencies
// - filter by visibility
// 2. For each of these, go up the module tree until we find an
// item/module/crate that is already in scope (including because it is in
// the prelude, and including aliases!)
// 3. Then select the one that gives the shortest path
// Base cases:
// - if the item is already in scope, return the name under which it is
let def_map = db.crate_def_map(from.krate);
let from_scope: &crate::item_scope::ItemScope = &def_map.modules[from.local_id].scope;
if let Some((name, _)) = from_scope.reverse_get(item) {
return Some(ModPath::from_simple_segments(PathKind::Plain, vec![name.clone()]));
}
// - if the item is the crate root, return `crate`
if item == ItemInNs::Types(ModuleDefId::ModuleId(ModuleId { krate: from.krate, local_id: def_map.root })) {
return Some(ModPath::from_simple_segments(PathKind::Crate, Vec::new()));
}
// - if the item is the crate root of a dependency crate, return the name from the extern prelude
for (name, def_id) in &def_map.extern_prelude {
if item == ItemInNs::Types(*def_id) {
return Some(ModPath::from_simple_segments(PathKind::Plain, vec![name.clone()]));
}
}
// - if the item is in the prelude, return the name from there
// TODO check prelude
// Recursive case:
// - if the item is an enum variant, refer to it via the enum
// - otherwise, look for modules containing (reexporting) it and import it from one of those
let importable_locations = find_importable_locations(db, item, from);
// XXX going in order for now
for (module_id, name) in importable_locations {
// TODO prevent infinite loops
let mut path = match find_path(db, ItemInNs::Types(ModuleDefId::ModuleId(module_id)), from) {
None => continue,
Some(path) => path,
};
path.segments.push(name);
return Some(path);
}
None
}
fn find_importable_locations(db: &impl DefDatabase, item: ItemInNs, from: ModuleId) -> Vec<(ModuleId, Name)> {
let crate_graph = db.crate_graph();
let mut result = Vec::new();
for krate in Some(from.krate).into_iter().chain(crate_graph.dependencies(from.krate).map(|dep| dep.crate_id)) {
let def_map = db.crate_def_map(krate);
for (local_id, data) in def_map.modules.iter() {
if let Some((name, vis)) = data.scope.reverse_get(item) {
if vis.is_visible_from(db, from) {
result.push((ModuleId { krate, local_id }, name.clone()));
}
}
}
}
result
}
#[cfg(test)]
mod tests {
use super::*;
use crate::test_db::TestDB;
use hir_expand::hygiene::Hygiene;
use ra_db::fixture::WithFixture;
use ra_syntax::ast::AstNode;
/// `code` needs to contain a cursor marker; checks that `find_path` for the
/// item the `path` refers to returns that same path when called from the
/// module the cursor is in.
fn check_found_path(code: &str, path: &str) {
let (db, pos) = TestDB::with_position(code);
let module = db.module_for_file(pos.file_id);
let parsed_path_file = ra_syntax::SourceFile::parse(&format!("use {};", path));
let ast_path = parsed_path_file
.syntax_node()
.descendants()
.find_map(ra_syntax::ast::Path::cast)
.unwrap();
let mod_path = ModPath::from_src(ast_path, &Hygiene::new_unhygienic()).unwrap();
let crate_def_map = db.crate_def_map(module.krate);
let resolved = crate_def_map
.resolve_path(
&db,
module.local_id,
&mod_path,
crate::item_scope::BuiltinShadowMode::Module,
)
.0
.take_types()
.unwrap();
let found_path = find_path(&db, ItemInNs::Types(resolved), module);
assert_eq!(found_path, Some(mod_path));
}
#[test]
fn same_module() {
let code = r#"
//- /main.rs
struct S;
<|>
"#;
check_found_path(code, "S");
}
#[test]
fn sub_module() {
let code = r#"
//- /main.rs
mod foo {
pub struct S;
}
<|>
"#;
check_found_path(code, "foo::S");
}
#[test]
fn crate_root() {
let code = r#"
//- /main.rs
mod foo;
//- /foo.rs
<|>
"#;
check_found_path(code, "crate");
}
#[test]
fn same_crate() {
let code = r#"
//- /main.rs
mod foo;
struct S;
//- /foo.rs
<|>
"#;
check_found_path(code, "crate::S");
}
#[test]
fn different_crate() {
let code = r#"
//- /main.rs crate:main deps:std
<|>
//- /std.rs crate:std
pub struct S;
"#;
check_found_path(code, "std::S");
}
#[test]
fn different_crate_renamed() {
let code = r#"
//- /main.rs crate:main deps:std
extern crate std as std_renamed;
<|>
//- /std.rs crate:std
pub struct S;
"#;
check_found_path(code, "std_renamed::S");
}
#[test]
fn same_crate_reexport() {
let code = r#"
//- /main.rs
mod bar {
mod foo { pub(super) struct S; }
pub(crate) use foo::*;
}
<|>
"#;
check_found_path(code, "bar::S");
}
#[test]
fn same_crate_reexport_rename() {
let code = r#"
//- /main.rs
mod bar {
mod foo { pub(super) struct S; }
pub(crate) use foo::S as U;
}
<|>
"#;
check_found_path(code, "bar::U");
}
#[test]
fn prelude() {
let code = r#"
//- /main.rs crate:main deps:std
<|>
//- /std.rs crate:std
pub mod prelude { pub struct S; }
#[prelude_import]
pub use prelude::*;
"#;
check_found_path(code, "S");
}
}
|
