Sort import alphabetically when formatting.

Fixes #211.

crates/aiken-lang/src/format.rs

@@ -133,14 +133,14 @@ impl<'comments> Formatter<'comments> {
             let start = def.location().start;
 
             match def {
-                Definition::Use { .. } => {
+                Definition::Use(import) => {
                     has_imports = true;
 
                     let comments = self.pop_comments(start);
 
                     let def = self.definition(def);
 
-                    imports.push(commented(def, comments))
+                    imports.push((import, commented(def, comments)))
                 }
 
                 _other => {
@@ -155,7 +155,15 @@ impl<'comments> Formatter<'comments> {
             }
         }
 
-        let imports = join(imports.into_iter(), line());
+        let imports = join(
+            imports
+                .into_iter()
+                .sorted_by(|(import_a, _), (import_b, _)| {
+                    Ord::cmp(&import_a.module, &import_b.module)
+                })
+                .map(|(_, doc)| doc),
+            line(),
+        );
 
         let declarations = join(declarations.into_iter(), lines(2));
 
@@ -253,12 +261,35 @@ impl<'comments> Formatter<'comments> {
                 ..
             }) => self.data_type(*public, *opaque, name, parameters, constructors, location),
 
-            Definition::Use(Use {
+            Definition::Use(import) => self.import(import),
+
+            Definition::ModuleConstant(ModuleConstant {
+                public,
+                name,
+                annotation,
+                value,
+                ..
+            }) => {
+                let head = pub_(*public).append("const ").append(name.as_str());
+                let head = match annotation {
+                    None => head,
+                    Some(t) => head.append(": ").append(self.annotation(t)),
+                };
+                head.append(" = ").append(self.const_expr(value))
+            }
+        }
+    }
+
+    fn import<'a>(
+        &mut self,
+        Use {
             module,
             as_name,
             unqualified,
             ..
-            }) => "use "
+        }: &'a Use<()>,
+    ) -> Document<'a> {
+        "use "
             .to_doc()
             .append(Document::String(module.join("/")))
             .append(if unqualified.is_empty() {
@@ -282,23 +313,7 @@ impl<'comments> Formatter<'comments> {
                 docvec![" as ", name]
             } else {
                 nil()
-                }),
-
-            Definition::ModuleConstant(ModuleConstant {
-                public,
-                name,
-                annotation,
-                value,
-                ..
-            }) => {
-                let head = pub_(*public).append("const ").append(name.as_str());
-                let head = match annotation {
-                    None => head,
-                    Some(t) => head.append(": ").append(self.annotation(t)),
-                };
-                head.append(" = ").append(self.const_expr(value))
-            }
-        }
+            })
     }
 
     fn const_expr<'a, A, B>(&mut self, value: &'a Constant<A, B>) -> Document<'a> {

crates/aiken-lang/src/tests/format.rs

@@ -5,14 +5,15 @@ use pretty_assertions::assert_eq;
 fn assert_fmt(src: &str, expected: &str) {
     let (module, extra) = parser::module(src, ModuleKind::Lib).unwrap();
     let mut out = String::new();
-    format::pretty(&mut out, module.clone(), extra.clone(), src);
+    format::pretty(&mut out, module, extra, src);
 
     // Output is what we expect
     assert_eq!(out, expected);
 
     // Formatting is idempotent
+    let (module2, extra2) = parser::module(&out, ModuleKind::Lib).unwrap();
     let mut out2 = String::new();
-    format::pretty(&mut out2, module, extra, &out);
+    format::pretty(&mut out2, module2, extra2, &out);
     assert_eq!(out, out2);
 }
 
@@ -171,3 +172,28 @@ fn test_format_nested_when() {
 
     assert_fmt(src, expected)
 }
+
+#[test]
+fn test_format_imports() {
+    let src = indoc! {r#"
+        use aiken/list
+        // foo
+        use aiken/bytearray
+        use aiken/transaction/certificate
+        // bar
+        use aiken/transaction
+        use aiken/transaction/value
+    "#};
+
+    let expected = indoc! {r#"
+        // foo
+        use aiken/bytearray
+        use aiken/list
+        // bar
+        use aiken/transaction
+        use aiken/transaction/certificate
+        use aiken/transaction/value
+    "#};
+
+    assert_fmt(src, expected)
+}