Add ModuleScope as a query

This is a first step towards queryifing completion and resolve.

Some code currently duplicates ra_editor: the plan is to move all
completion from ra_editor, but it'll take more than one commit.

8 files changed, 223 insertions, 22 deletions

diff --git a/crates/ra_analysis/src/completion.rs b/crates/ra_analysis/src/completion.rs
index 0a2f99575..0141d132e 100644
--- a/crates/ra_analysis/src/completion.rs
+++ b/crates/ra_analysis/src/completion.rs
@@ -1,40 +1,51 @@
-use ra_editor::{CompletionItem, find_node_at_offset, complete_module_items};
+use ra_editor::{CompletionItem, find_node_at_offset};
 use ra_syntax::{
     AtomEdit, File, TextUnit, AstNode,
-    ast::{self, ModuleItemOwner},
+    ast::{self, ModuleItemOwner, AstChildren},
 };
 
 use crate::{
     FileId, Cancelable,
     input::FilesDatabase,
     db::{self, SyntaxDatabase},
-    descriptors::module::{ModulesDatabase, ModuleTree, ModuleId},
+    descriptors::module::{ModulesDatabase, ModuleTree, ModuleId, scope::ModuleScope},
 };
 
 pub(crate) fn resolve_based_completion(db: &db::RootDatabase, file_id: FileId, offset: TextUnit) -> Cancelable<Option<Vec<CompletionItem>>> {
     let source_root_id = db.file_source_root(file_id);
     let file = db.file_syntax(file_id);
     let module_tree = db.module_tree(source_root_id)?;
+    let module_id = match module_tree.any_module_for_file(file_id) {
+        None => return Ok(None),
+        Some(it) => it,
+    };
     let file = {
         let edit = AtomEdit::insert(offset, "intellijRulezz".to_string());
         file.reparse(&edit)
     };
-    let target_file = match find_target_module(&module_tree, file_id, &file, offset) {
+    let target_module_id = match find_target_module(&module_tree, module_id, &file, offset) {
         None => return Ok(None),
-        Some(target_module) => {
-            let file_id = target_module.file_id(&module_tree);
-            db.file_syntax(file_id)
-        }
+        Some(it) => it,
     };
-    let mut res = Vec::new();
-    complete_module_items(target_file.ast().items(), None, &mut res);
+    let module_scope = db.module_scope(source_root_id, target_module_id)?;
+    let res: Vec<_> = module_scope
+        .entries()
+        .iter()
+        .map(|entry| CompletionItem {
+            label: entry.name().to_string(),
+            lookup: None,
+            snippet: None,
+        })
+        .collect();
     Ok(Some(res))
 }
 
-pub(crate) fn find_target_module(module_tree: &ModuleTree, file_id: FileId, file: &File, offset: TextUnit) -> Option<ModuleId> {
+
+
+pub(crate) fn find_target_module(module_tree: &ModuleTree, module_id: ModuleId, file: &File, offset: TextUnit) -> Option<ModuleId> {
     let name_ref: ast::NameRef = find_node_at_offset(file.syntax(), offset)?;
     let mut crate_path = crate_path(name_ref)?;
-    let module_id = module_tree.any_module_for_file(file_id)?;
+
     crate_path.pop();
     let mut target_module = module_id.root(&module_tree);
     for name in crate_path {
diff --git a/crates/ra_analysis/src/db.rs b/crates/ra_analysis/src/db.rs
index 3ca14af79..e7a5d5e2f 100644
--- a/crates/ra_analysis/src/db.rs
+++ b/crates/ra_analysis/src/db.rs
@@ -9,8 +9,9 @@ use salsa;
 use crate::{
     db,
     Cancelable, Canceled,
-    descriptors::module::{SubmodulesQuery, ModuleTreeQuery, ModulesDatabase},
+    descriptors::module::{SubmodulesQuery, ModuleTreeQuery, ModulesDatabase, ModuleScopeQuery},
     symbol_index::SymbolIndex,
+    syntax_ptr::{SyntaxPtrDatabase, ResolveSyntaxPtrQuery},
     FileId,
 };
 
@@ -65,6 +66,10 @@ salsa::database_storage! {
         impl ModulesDatabase {
             fn module_tree() for ModuleTreeQuery;
             fn module_descriptor() for SubmodulesQuery;
+            fn module_scope() for ModuleScopeQuery;
+        }
+        impl SyntaxPtrDatabase {
+            fn resolve_syntax_ptr() for ResolveSyntaxPtrQuery;
         }
     }
 }
diff --git a/crates/ra_analysis/src/descriptors/module/imp.rs b/crates/ra_analysis/src/descriptors/module/imp.rs
index aecf6e29a..5fdaad137 100644
--- a/crates/ra_analysis/src/descriptors/module/imp.rs
+++ b/crates/ra_analysis/src/descriptors/module/imp.rs
@@ -13,7 +13,7 @@ use crate::{
 };
 
 use super::{
-    ModuleData, ModuleTree, ModuleId, LinkId, LinkData, Problem, ModulesDatabase
+    ModuleData, ModuleTree, ModuleId, LinkId, LinkData, Problem, ModulesDatabase, ModuleScope
 };
 
 
@@ -35,6 +35,18 @@ pub(super) fn modules(root: ast::Root<'_>) -> impl Iterator<Item = (SmolStr, ast
     })
 }
 
+pub(super) fn module_scope(
+    db: &impl ModulesDatabase,
+    source_root_id: SourceRootId,
+    module_id: ModuleId,
+) -> Cancelable<Arc<ModuleScope>> {
+    let tree = db.module_tree(source_root_id)?;
+    let file_id = module_id.file_id(&tree);
+    let syntax = db.file_syntax(file_id);
+    let res = ModuleScope::new(&syntax);
+    Ok(Arc::new(res))
+}
+
 pub(super) fn module_tree(
     db: &impl ModulesDatabase,
     source_root: SourceRootId,
diff --git a/crates/ra_analysis/src/descriptors/module/mod.rs b/crates/ra_analysis/src/descriptors/module/mod.rs
index 8968c4afd..9e5d73f94 100644
--- a/crates/ra_analysis/src/descriptors/module/mod.rs
+++ b/crates/ra_analysis/src/descriptors/module/mod.rs
@@ -1,4 +1,5 @@
 mod imp;
+pub(crate) mod scope;
 
 use std::sync::Arc;
 
@@ -11,6 +12,8 @@ use crate::{
     input::SourceRootId,
 };
 
+pub(crate) use self::scope::ModuleScope;
+
 salsa::query_group! {
     pub(crate) trait ModulesDatabase: SyntaxDatabase {
         fn module_tree(source_root_id: SourceRootId) -> Cancelable<Arc<ModuleTree>> {
@@ -21,6 +24,10 @@ salsa::query_group! {
             type SubmodulesQuery;
             use fn imp::submodules;
         }
+        fn module_scope(source_root_id: SourceRootId, module_id: ModuleId) -> Cancelable<Arc<ModuleScope>> {
+            type ModuleScopeQuery;
+            use fn imp::module_scope;
+        }
     }
 }
 
@@ -78,6 +85,7 @@ impl ModuleId {
         while let Some(next) = curr.parent(tree) {
             curr = next;
             i += 1;
+            // simplistic cycle detection
             if i > 100 {
                 return self;
             }
diff --git a/crates/ra_analysis/src/descriptors/module/scope.rs b/crates/ra_analysis/src/descriptors/module/scope.rs
new file mode 100644
index 000000000..da58ddce0
--- /dev/null
+++ b/crates/ra_analysis/src/descriptors/module/scope.rs
@@ -0,0 +1,128 @@
+//! Backend for module-level scope resolution & completion
+
+
+use ra_syntax::{
+    ast::{self, AstChildren, ModuleItemOwner},
+    File, AstNode, SmolStr, SyntaxNode, SyntaxNodeRef,
+};
+
+use crate::syntax_ptr::LocalSyntaxPtr;
+
+/// `ModuleScope` contains all named items declared in the scope.
+#[derive(Debug, PartialEq, Eq)]
+pub(crate) struct ModuleScope {
+    entries: Vec<Entry>,
+}
+
+/// `Entry` is a single named declaration iside a module.
+#[derive(Debug, PartialEq, Eq)]
+pub(crate) struct Entry {
+    ptr: LocalSyntaxPtr,
+    kind: EntryKind,
+    name: SmolStr,
+}
+
+#[derive(Debug, PartialEq, Eq)]
+enum EntryKind {
+    Item,
+    Import,
+}
+
+impl ModuleScope {
+    pub fn new(file: &File) -> ModuleScope {
+        let mut entries = Vec::new();
+        for item in file.ast().items() {
+            let entry = match item {
+                ast::ModuleItem::StructDef(item) => Entry::new(item),
+                ast::ModuleItem::EnumDef(item) => Entry::new(item),
+                ast::ModuleItem::FnDef(item) => Entry::new(item),
+                ast::ModuleItem::ConstDef(item) => Entry::new(item),
+                ast::ModuleItem::StaticDef(item) => Entry::new(item),
+                ast::ModuleItem::TraitDef(item) => Entry::new(item),
+                ast::ModuleItem::TypeDef(item) => Entry::new(item),
+                ast::ModuleItem::Module(item) => Entry::new(item),
+                ast::ModuleItem::UseItem(item) => {
+                    if let Some(tree) = item.use_tree() {
+                        collect_imports(tree, &mut entries);
+                    }
+                    continue;
+                }
+                ast::ModuleItem::ExternCrateItem(_) | ast::ModuleItem::ImplItem(_) => continue,
+            };
+            entries.extend(entry)
+        }
+
+        ModuleScope { entries }
+    }
+
+    pub fn entries(&self) -> &[Entry] {
+        self.entries.as_slice()
+    }
+}
+
+impl Entry {
+    fn new<'a>(item: impl ast::NameOwner<'a>) -> Option<Entry> {
+        let name = item.name()?;
+        Some(Entry {
+            name: name.text(),
+            ptr: LocalSyntaxPtr::new(name.syntax()),
+            kind: EntryKind::Item,
+        })
+    }
+    fn new_import(path: ast::Path) -> Option<Entry> {
+        let name_ref = path.segment()?.name_ref()?;
+        Some(Entry {
+            name: name_ref.text(),
+            ptr: LocalSyntaxPtr::new(name_ref.syntax()),
+            kind: EntryKind::Import,
+        })
+    }
+    pub fn name(&self) -> &SmolStr {
+        &self.name
+    }
+    pub fn ptr(&self) -> LocalSyntaxPtr {
+        self.ptr
+    }
+}
+
+fn collect_imports(tree: ast::UseTree, acc: &mut Vec<Entry>) {
+    if let Some(use_tree_list) = tree.use_tree_list() {
+        return use_tree_list
+            .use_trees()
+            .for_each(|it| collect_imports(it, acc));
+    }
+    if let Some(path) = tree.path() {
+        acc.extend(Entry::new_import(path));
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use ra_syntax::{ast::ModuleItemOwner, File};
+
+    fn do_check(code: &str, expected: &[&str]) {
+        let file = File::parse(&code);
+        let scope = ModuleScope::new(&file);
+        let actual = scope.entries.iter().map(|it| it.name()).collect::<Vec<_>>();
+        assert_eq!(expected, actual.as_slice());
+    }
+
+    #[test]
+    fn test_module_scope() {
+        do_check(
+            "
+            struct Foo;
+            enum Bar {}
+            mod baz {}
+            fn quux() {}
+            use x::{
+                y::z,
+                t,
+            };
+            type T = ();
+        ",
+            &["Foo", "Bar", "baz", "quux", "z", "t", "T"],
+        )
+    }
+}
diff --git a/crates/ra_analysis/src/syntax_ptr.rs b/crates/ra_analysis/src/syntax_ptr.rs
index 863ad2672..adbff4806 100644
--- a/crates/ra_analysis/src/syntax_ptr.rs
+++ b/crates/ra_analysis/src/syntax_ptr.rs
@@ -1,3 +1,5 @@
+use std::marker::PhantomData;
+
 use ra_syntax::{
     File, TextRange, SyntaxKind, SyntaxNode, SyntaxNodeRef,
     ast::{self, AstNode},
@@ -6,10 +8,24 @@ use ra_syntax::{
 use crate::FileId;
 use crate::db::SyntaxDatabase;
 
+salsa::query_group! {
+    pub(crate) trait SyntaxPtrDatabase: SyntaxDatabase {
+        fn resolve_syntax_ptr(ptr: SyntaxPtr) -> SyntaxNode {
+            type ResolveSyntaxPtrQuery;
+            storage volatile;
+        }
+    }
+}
+
+fn resolve_syntax_ptr(db: &impl SyntaxDatabase, ptr: SyntaxPtr) -> SyntaxNode {
+    let syntax = db.file_syntax(ptr.file_id);
+    ptr.local.resolve(&syntax)
+}
+
 /// SyntaxPtr is a cheap `Copy` id which identifies a particular syntax node,
 /// without retainig syntax tree in memory. You need to explicitelly `resovle`
 /// `SyntaxPtr` to get a `SyntaxNode`
-#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
 pub(crate) struct SyntaxPtr {
     file_id: FileId,
     local: LocalSyntaxPtr,
@@ -20,30 +36,43 @@ impl SyntaxPtr {
         let local = LocalSyntaxPtr::new(node);
         SyntaxPtr { file_id, local }
     }
+}
+
+struct OwnedAst<T> {
+    syntax: SyntaxNode,
+    phantom: PhantomData<T>,
+}
+
+trait ToAst {
+    type Ast;
+    fn to_ast(self) -> Self::Ast;
+}
 
-    pub(crate) fn resolve(self, db: &impl SyntaxDatabase) -> SyntaxNode {
-        let syntax = db.file_syntax(self.file_id);
-        self.local.resolve(&syntax)
+impl<'a> ToAst for &'a OwnedAst<ast::FnDef<'static>> {
+    type Ast = ast::FnDef<'a>;
+    fn to_ast(self) -> ast::FnDef<'a> {
+        ast::FnDef::cast(self.syntax.borrowed())
+            .unwrap()
     }
 }
 
 
 /// A pionter to a syntax node inside a file.
-#[derive(Debug, Clone, Copy, PartialEq, Eq)]
-struct LocalSyntaxPtr {
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub(crate) struct LocalSyntaxPtr {
     range: TextRange,
     kind: SyntaxKind,
 }
 
 impl LocalSyntaxPtr {
-    fn new(node: SyntaxNodeRef) -> LocalSyntaxPtr {
+    pub(crate) fn new(node: SyntaxNodeRef) -> LocalSyntaxPtr {
         LocalSyntaxPtr {
             range: node.range(),
             kind: node.kind(),
         }
     }
 
-    fn resolve(self, file: &File) -> SyntaxNode {
+    pub(crate) fn resolve(self, file: &File) -> SyntaxNode {
         let mut curr = file.syntax();
         loop {
             if curr.range() == self.range && curr.kind() == self.kind {
diff --git a/crates/ra_editor/src/completion.rs b/crates/ra_editor/src/completion.rs
index a0b168bc6..20c8546a4 100644
--- a/crates/ra_editor/src/completion.rs
+++ b/crates/ra_editor/src/completion.rs
@@ -1,3 +1,5 @@
+/// FIXME: move completion from ra_editor to ra_analysis
+
 use rustc_hash::{FxHashMap, FxHashSet};
 
 use ra_syntax::{
diff --git a/crates/ra_editor/src/scope/mod_scope.rs b/crates/ra_editor/src/scope/mod_scope.rs
index 956ee0e2f..818749a12 100644
--- a/crates/ra_editor/src/scope/mod_scope.rs
+++ b/crates/ra_editor/src/scope/mod_scope.rs
@@ -1,3 +1,9 @@
+/// FIXME: this is now moved to ra_analysis::descriptors::module::scope.
+///
+/// Current copy will be deleted as soon as we move the rest of the completion
+/// to the analyezer.
+
+
 use ra_syntax::{
     ast::{self, AstChildren},
     AstNode, SmolStr, SyntaxNode, SyntaxNodeRef,