1 files changed, 145 insertions, 0 deletions

diff --git a/crates/assists/src/handlers/move_module_to_file.rs b/crates/assists/src/handlers/move_module_to_file.rs
new file mode 100644
index 000000000..9d8579f47
--- /dev/null
+++ b/crates/assists/src/handlers/move_module_to_file.rs
@@ -0,0 +1,145 @@
+use ast::edit::IndentLevel;
+use ide_db::base_db::AnchoredPathBuf;
+use syntax::{
+    ast::{self, edit::AstNodeEdit, NameOwner},
+    AstNode, TextRange,
+};
+use test_utils::mark;
+
+use crate::{AssistContext, AssistId, AssistKind, Assists};
+
+// Assist: move_module_to_file
+//
+// Moves inline module's contents to a separate file.
+//
+// ```
+// mod $0foo {
+//     fn t() {}
+// }
+// ```
+// ->
+// ```
+// mod foo;
+// ```
+pub(crate) fn move_module_to_file(acc: &mut Assists, ctx: &AssistContext) -> Option<()> {
+    let module_ast = ctx.find_node_at_offset::<ast::Module>()?;
+    let module_items = module_ast.item_list()?;
+
+    let l_curly_offset = module_items.syntax().text_range().start();
+    if l_curly_offset <= ctx.offset() {
+        mark::hit!(available_before_curly);
+        return None;
+    }
+    let target = TextRange::new(module_ast.syntax().text_range().start(), l_curly_offset);
+
+    let module_name = module_ast.name()?;
+
+    let module_def = ctx.sema.to_def(&module_ast)?;
+    let parent_module = module_def.parent(ctx.db())?;
+
+    acc.add(
+        AssistId("move_module_to_file", AssistKind::RefactorExtract),
+        "Extract module to file",
+        target,
+        |builder| {
+            let path = {
+                let dir = match parent_module.name(ctx.db()) {
+                    Some(name) if !parent_module.is_mod_rs(ctx.db()) => format!("{}/", name),
+                    _ => String::new(),
+                };
+                format!("./{}{}.rs", dir, module_name)
+            };
+            let contents = {
+                let items = module_items.dedent(IndentLevel(1)).to_string();
+                let mut items =
+                    items.trim_start_matches('{').trim_end_matches('}').trim().to_string();
+                if !items.is_empty() {
+                    items.push('\n');
+                }
+                items
+            };
+
+            builder.replace(module_ast.syntax().text_range(), format!("mod {};", module_name));
+
+            let dst = AnchoredPathBuf { anchor: ctx.frange.file_id, path };
+            builder.create_file(dst, contents);
+        },
+    )
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::tests::{check_assist, check_assist_not_applicable};
+
+    use super::*;
+
+    #[test]
+    fn extract_from_root() {
+        check_assist(
+            move_module_to_file,
+            r#"
+mod $0tests {
+    #[test] fn t() {}
+}
+"#,
+            r#"
+//- /main.rs
+mod tests;
+//- /tests.rs
+#[test] fn t() {}
+"#,
+        );
+    }
+
+    #[test]
+    fn extract_from_submodule() {
+        check_assist(
+            move_module_to_file,
+            r#"
+//- /main.rs
+mod submod;
+//- /submod.rs
+$0mod inner {
+    fn f() {}
+}
+fn g() {}
+"#,
+            r#"
+//- /submod.rs
+mod inner;
+fn g() {}
+//- /submod/inner.rs
+fn f() {}
+"#,
+        );
+    }
+
+    #[test]
+    fn extract_from_mod_rs() {
+        check_assist(
+            move_module_to_file,
+            r#"
+//- /main.rs
+mod submodule;
+//- /submodule/mod.rs
+mod inner$0 {
+    fn f() {}
+}
+fn g() {}
+"#,
+            r#"
+//- /submodule/mod.rs
+mod inner;
+fn g() {}
+//- /submodule/inner.rs
+fn f() {}
+"#,
+        );
+    }
+
+    #[test]
+    fn available_before_curly() {
+        mark::check!(available_before_curly);
+        check_assist_not_applicable(move_module_to_file, r#"mod m { $0 }"#);
+    }
+}