1 files changed, 77 insertions, 0 deletions

diff --git a/crates/ra_ide_api/src/completion.rs b/crates/ra_ide_api/src/completion.rs
new file mode 100644
index 000000000..ce777a771
--- /dev/null
+++ b/crates/ra_ide_api/src/completion.rs
@@ -0,0 +1,77 @@
+mod completion_item;
+mod completion_context;
+
+mod complete_dot;
+mod complete_fn_param;
+mod complete_keyword;
+mod complete_snippet;
+mod complete_path;
+mod complete_scope;
+
+use ra_db::SyntaxDatabase;
+
+use crate::{
+    db,
+    Cancelable, FilePosition,
+    completion::{
+        completion_item::{Completions, CompletionKind},
+        completion_context::CompletionContext,
+    },
+};
+
+pub use crate::completion::completion_item::{CompletionItem, InsertText, CompletionItemKind};
+
+/// Main entry point for completion. We run completion as a two-phase process.
+///
+/// First, we look at the position and collect a so-called `CompletionContext.
+/// This is a somewhat messy process, because, during completion, syntax tree is
+/// incomplete and can look really weird.
+///
+/// Once the context is collected, we run a series of completion routines which
+/// look at the context and produce completion items. One subtelty about this
+/// phase is that completion engine should not filter by the substring which is
+/// already present, it should give all possible variants for the identifier at
+/// the caret. In other words, for
+///
+/// ```no-run
+/// fn f() {
+///     let foo = 92;
+///     let _ = bar<|>
+/// }
+/// ```
+///
+/// `foo` *should* be present among the completion variants. Filtering by
+/// identifier prefix/fuzzy match should be done higher in the stack, together
+/// with ordering of completions (currently this is done by the client).
+pub(crate) fn completions(
+    db: &db::RootDatabase,
+    position: FilePosition,
+) -> Cancelable<Option<Completions>> {
+    let original_file = db.source_file(position.file_id);
+    let ctx = ctry!(CompletionContext::new(db, &original_file, position)?);
+
+    let mut acc = Completions::default();
+
+    complete_fn_param::complete_fn_param(&mut acc, &ctx);
+    complete_keyword::complete_expr_keyword(&mut acc, &ctx);
+    complete_keyword::complete_use_tree_keyword(&mut acc, &ctx);
+    complete_snippet::complete_expr_snippet(&mut acc, &ctx);
+    complete_snippet::complete_item_snippet(&mut acc, &ctx);
+    complete_path::complete_path(&mut acc, &ctx)?;
+    complete_scope::complete_scope(&mut acc, &ctx)?;
+    complete_dot::complete_dot(&mut acc, &ctx)?;
+
+    Ok(Some(acc))
+}
+
+#[cfg(test)]
+fn check_completion(code: &str, expected_completions: &str, kind: CompletionKind) {
+    use crate::mock_analysis::{single_file_with_position, analysis_and_position};
+    let (analysis, position) = if code.contains("//-") {
+        analysis_and_position(code)
+    } else {
+        single_file_with_position(code)
+    };
+    let completions = completions(&analysis.db, position).unwrap().unwrap();
+    completions.assert_match(expected_completions, kind);
+}