fix: fix formatter adding -- to multiple use statements (#773)

* fix: fix formatter adding `--` to multiple `use` statements
* docs: update the workaround for the formatter: it turns out that we can format parsing but non-compiling code

docs/src/getting-started/temporary_workarounds.md

@@ -65,4 +65,4 @@ The optimizing pass of the compiler is not yet implemented, therefore bytecode w
 
 ## Formatter
 
-Currently, we need to parse the Sway code before formatting it, and the best way to do this is to compile the code. Hence, **the formatter cannot work on Sway code that does not compile**. This requirement may be changed in the future.
+Currently, we need to parse the Sway code before formatting it. Hence, **the formatter cannot work on Sway code that does not parse correctly**. This requirement may be changed in the future.

sway-fmt/src/fmt.rs

@@ -641,4 +641,23 @@ fn one_liner() -> bool {
         let (_, formatted_code) = result.unwrap();
         assert_eq!(correct_sway_code, formatted_code);
     }
+
+    #[test]
+    // Test that the use statements with multiple imports are properly formatted
+    fn test_use_statement() {
+        let expected_sway = r#"script;
+use std::chain::{panic,log_u8};
+use std::chain::assert;
+use std::hash::{HashMethod,hash_value,hash_pair};
+use a::b::{c,d::{e,f}};
+use a::b::{c,d::{self,f}};
+
+fn main() {
+}
+"#;
+        let result = get_formatted_data(expected_sway.into(), OPTIONS);
+        assert!(result.is_ok());
+        let (_, formatted_code) = result.unwrap();
+        assert_eq!(formatted_code, expected_sway);
+    }
 }

sway-fmt/src/traversal.rs

@@ -48,7 +48,7 @@ pub fn traverse_for_changes(parse_tree: &SwayParseTree) -> Vec<Change> {
     let mut changes = vec![];
 
     for node in &parse_tree.tree.root_nodes {
-        traverse_ast_node(node, &mut changes)
+        traverse_ast_node(node, &mut changes);
     }
 
     changes.sort_by(|a, b| a.start.cmp(&b.start));
@@ -69,7 +69,17 @@ fn traverse_ast_node(ast_node: &AstNode, changes: &mut Vec<Change>) {
         }
 
         AstNodeContent::UseStatement(_) => {
-            changes.push(Change::new(&ast_node.span, ChangeType::UseStatement));
+            // The AST generates one root node per use statement, we must avoid duplicating them
+            // while formatting
+            let next_span = &ast_node.span;
+            match changes.last() {
+                Some(last_change) => {
+                    if last_change.start != next_span.start() {
+                        changes.push(Change::new(next_span, ChangeType::UseStatement));
+                    }
+                }
+                _ => changes.push(Change::new(next_span, ChangeType::UseStatement)),
+            }
         }
 
         AstNodeContent::IncludeStatement(_) => {