Merge #750

750: Move assists to a separate crate r=matklad a=matklad

I am slowly coming to conclusion that ide_api_light does not make a lot of sense after all :D 

This PR moves assists to a separate crate, so that assists can use database (so, inspect types, do name-resolution, etc)

Co-authored-by: Aleksey Kladov <[email protected]>

1 files changed, 170 insertions, 0 deletions

diff --git a/crates/ra_assists/src/lib.rs b/crates/ra_assists/src/lib.rs
new file mode 100644
index 000000000..4e97a84c2
--- /dev/null
+++ b/crates/ra_assists/src/lib.rs
@@ -0,0 +1,170 @@
+//! `ra_assits` crate provides a bunch of code assists, aslo known as code
+//! actions (in LSP) or intentions (in IntelliJ).
+//!
+//! An assist is a micro-refactoring, which is automatically activated in
+//! certain context. For example, if the cursor is over `,`, a "swap `,`" assist
+//! becomes available.
+
+mod assist_ctx;
+
+use ra_text_edit::TextEdit;
+use ra_syntax::{TextUnit, SyntaxNode, Direction};
+use ra_db::FileRange;
+use hir::db::HirDatabase;
+
+pub(crate) use crate::assist_ctx::{AssistCtx, Assist};
+
+#[derive(Debug)]
+pub struct AssistLabel {
+    /// Short description of the assist, as shown in the UI.
+    pub label: String,
+}
+
+pub struct AssistAction {
+    pub edit: TextEdit,
+    pub cursor_position: Option<TextUnit>,
+}
+
+/// Return all the assists applicable at the given position.
+///
+/// Assists are returned in the "unresolved" state, that is only labels are
+/// returned, without actual edits.
+pub fn applicable_assists<H>(db: &H, range: FileRange) -> Vec<AssistLabel>
+where
+    H: HirDatabase + 'static,
+{
+    AssistCtx::with_ctx(db, range, false, |ctx| {
+        all_assists()
+            .iter()
+            .filter_map(|f| f(ctx.clone()))
+            .map(|a| match a {
+                Assist::Unresolved(label) => label,
+                Assist::Resolved(..) => unreachable!(),
+            })
+            .collect()
+    })
+}
+
+/// Return all the assists applicable at the given position.
+///
+/// Assists are returned in the "resolved" state, that is with edit fully
+/// computed.
+pub fn assists<H>(db: &H, range: FileRange) -> Vec<(AssistLabel, AssistAction)>
+where
+    H: HirDatabase + 'static,
+{
+    AssistCtx::with_ctx(db, range, false, |ctx| {
+        all_assists()
+            .iter()
+            .filter_map(|f| f(ctx.clone()))
+            .map(|a| match a {
+                Assist::Resolved(label, action) => (label, action),
+                Assist::Unresolved(..) => unreachable!(),
+            })
+            .collect()
+    })
+}
+
+mod add_derive;
+mod add_impl;
+mod flip_comma;
+mod change_visibility;
+mod fill_match_arms;
+mod introduce_variable;
+mod replace_if_let_with_match;
+mod split_import;
+fn all_assists<DB: HirDatabase>() -> &'static [fn(AssistCtx<DB>) -> Option<Assist>] {
+    &[
+        add_derive::add_derive,
+        add_impl::add_impl,
+        change_visibility::change_visibility,
+        fill_match_arms::fill_match_arms,
+        flip_comma::flip_comma,
+        introduce_variable::introduce_variable,
+        replace_if_let_with_match::replace_if_let_with_match,
+        split_import::split_import,
+    ]
+}
+
+fn non_trivia_sibling(node: &SyntaxNode, direction: Direction) -> Option<&SyntaxNode> {
+    node.siblings(direction)
+        .skip(1)
+        .find(|node| !node.kind().is_trivia())
+}
+
+#[cfg(test)]
+mod helpers {
+    use hir::mock::MockDatabase;
+    use ra_syntax::TextRange;
+    use ra_db::FileRange;
+    use test_utils::{extract_offset, assert_eq_text, add_cursor, extract_range};
+
+    use crate::{AssistCtx, Assist};
+
+    pub(crate) fn check_assist(
+        assist: fn(AssistCtx<MockDatabase>) -> Option<Assist>,
+        before: &str,
+        after: &str,
+    ) {
+        let (before_cursor_pos, before) = extract_offset(before);
+        let (db, _source_root, file_id) = MockDatabase::with_single_file(&before);
+        let frange = FileRange {
+            file_id,
+            range: TextRange::offset_len(before_cursor_pos, 0.into()),
+        };
+        let assist =
+            AssistCtx::with_ctx(&db, frange, true, assist).expect("code action is not applicable");
+        let action = match assist {
+            Assist::Unresolved(_) => unreachable!(),
+            Assist::Resolved(_, it) => it,
+        };
+
+        let actual = action.edit.apply(&before);
+        let actual_cursor_pos = match action.cursor_position {
+            None => action
+                .edit
+                .apply_to_offset(before_cursor_pos)
+                .expect("cursor position is affected by the edit"),
+            Some(off) => off,
+        };
+        let actual = add_cursor(&actual, actual_cursor_pos);
+        assert_eq_text!(after, &actual);
+    }
+
+    pub(crate) fn check_assist_range(
+        assist: fn(AssistCtx<MockDatabase>) -> Option<Assist>,
+        before: &str,
+        after: &str,
+    ) {
+        let (range, before) = extract_range(before);
+        let (db, _source_root, file_id) = MockDatabase::with_single_file(&before);
+        let frange = FileRange { file_id, range };
+        let assist =
+            AssistCtx::with_ctx(&db, frange, true, assist).expect("code action is not applicable");
+        let action = match assist {
+            Assist::Unresolved(_) => unreachable!(),
+            Assist::Resolved(_, it) => it,
+        };
+
+        let mut actual = action.edit.apply(&before);
+        if let Some(pos) = action.cursor_position {
+            actual = add_cursor(&actual, pos);
+        }
+        assert_eq_text!(after, &actual);
+    }
+
+    pub(crate) fn check_assist_not_applicable(
+        assist: fn(AssistCtx<MockDatabase>) -> Option<Assist>,
+        before: &str,
+    ) {
+        let (before_cursor_pos, before) = extract_offset(before);
+        let (db, _source_root, file_id) = MockDatabase::with_single_file(&before);
+        let frange = FileRange {
+            file_id,
+            range: TextRange::offset_len(before_cursor_pos, 0.into()),
+        };
+        let assist = AssistCtx::with_ctx(&db, frange, true, assist);
+        assert!(assist.is_none());
+    }
+
+}