3 files changed, 247 insertions, 0 deletions

diff --git a/crates/ra_assists/src/doc_tests/generated.rs b/crates/ra_assists/src/doc_tests/generated.rs
index 24392836c..b63b4d81a 100644
--- a/crates/ra_assists/src/doc_tests/generated.rs
+++ b/crates/ra_assists/src/doc_tests/generated.rs
@@ -607,6 +607,21 @@ impl Walrus {
 }
 
 #[test]
+fn doctest_reorder_fields() {
+    check(
+        "reorder_fields",
+        r#####"
+struct Foo {foo: i32, bar: i32};
+const test: Foo = <|>Foo {bar: 0, foo: 1}
+"#####,
+        r#####"
+struct Foo {foo: i32, bar: i32};
+const test: Foo = Foo {foo: 1, bar: 0}
+"#####,
+    )
+}
+
+#[test]
 fn doctest_replace_if_let_with_match() {
     check(
         "replace_if_let_with_match",
diff --git a/crates/ra_assists/src/handlers/reorder_fields.rs b/crates/ra_assists/src/handlers/reorder_fields.rs
new file mode 100644
index 000000000..692dd1315
--- /dev/null
+++ b/crates/ra_assists/src/handlers/reorder_fields.rs
@@ -0,0 +1,230 @@
+use std::collections::HashMap;
+
+use itertools::Itertools;
+
+use hir::{Adt, ModuleDef, PathResolution, Semantics, Struct};
+use ra_ide_db::RootDatabase;
+use ra_syntax::{
+    algo, ast,
+    ast::{Name, Path, RecordLit, RecordPat},
+    AstNode, SyntaxKind, SyntaxNode,
+};
+
+use crate::{
+    assist_ctx::{Assist, AssistCtx},
+    AssistId,
+};
+use ra_syntax::ast::{Expr, NameRef};
+
+// Assist: reorder_fields
+//
+// Reorder the fields of record literals and record patterns in the same order as in
+// the definition.
+//
+// ```
+// struct Foo {foo: i32, bar: i32};
+// const test: Foo = <|>Foo {bar: 0, foo: 1}
+// ```
+// ->
+// ```
+// struct Foo {foo: i32, bar: i32};
+// const test: Foo = Foo {foo: 1, bar: 0}
+// ```
+//
+pub(crate) fn reorder_fields(ctx: AssistCtx) -> Option<Assist> {
+    reorder::<RecordLit>(ctx.clone()).or_else(|| reorder::<RecordPat>(ctx))
+}
+
+fn reorder<R: AstNode>(ctx: AssistCtx) -> Option<Assist> {
+    let record = ctx.find_node_at_offset::<R>()?;
+    let path = record.syntax().children().find_map(Path::cast)?;
+
+    let ranks = compute_fields_ranks(&path, &ctx)?;
+
+    let fields = get_fields(&record.syntax());
+    let sorted_fields = sorted_by_rank(&fields, |node| {
+        *ranks.get(&get_field_name(node)).unwrap_or(&usize::max_value())
+    });
+
+    if sorted_fields == fields {
+        return None;
+    }
+
+    ctx.add_assist(AssistId("reorder_fields"), "Reorder record fields", |edit| {
+        for (old, new) in fields.iter().zip(&sorted_fields) {
+            algo::diff(old, new).into_text_edit(edit.text_edit_builder());
+        }
+        edit.target(record.syntax().text_range())
+    })
+}
+
+fn get_fields_kind(node: &SyntaxNode) -> Vec<SyntaxKind> {
+    use SyntaxKind::*;
+    match node.kind() {
+        RECORD_LIT => vec![RECORD_FIELD],
+        RECORD_PAT => vec![RECORD_FIELD_PAT, BIND_PAT],
+        _ => vec![],
+    }
+}
+
+fn get_field_name(node: &SyntaxNode) -> String {
+    use SyntaxKind::*;
+    match node.kind() {
+        RECORD_FIELD => {
+            if let Some(name) = node.children().find_map(NameRef::cast) {
+                return name.to_string();
+            }
+            node.children().find_map(Expr::cast).map(|expr| expr.to_string()).unwrap_or_default()
+        }
+        BIND_PAT | RECORD_FIELD_PAT => {
+            node.children().find_map(Name::cast).map(|n| n.to_string()).unwrap_or_default()
+        }
+        _ => String::new(),
+    }
+}
+
+fn get_fields(record: &SyntaxNode) -> Vec<SyntaxNode> {
+    let kinds = get_fields_kind(record);
+    record.children().flat_map(|n| n.children()).filter(|n| kinds.contains(&n.kind())).collect()
+}
+
+fn sorted_by_rank(
+    fields: &[SyntaxNode],
+    get_rank: impl Fn(&SyntaxNode) -> usize,
+) -> Vec<SyntaxNode> {
+    fields.iter().cloned().sorted_by_key(get_rank).collect()
+}
+
+fn struct_definition(path: &ast::Path, sema: &Semantics<RootDatabase>) -> Option<Struct> {
+    match sema.resolve_path(path) {
+        Some(PathResolution::Def(ModuleDef::Adt(Adt::Struct(s)))) => Some(s),
+        _ => None,
+    }
+}
+
+fn compute_fields_ranks(path: &Path, ctx: &AssistCtx) -> Option<HashMap<String, usize>> {
+    Some(
+        struct_definition(path, ctx.sema)?
+            .fields(ctx.db)
+            .iter()
+            .enumerate()
+            .map(|(idx, field)| (field.name(ctx.db).to_string(), idx))
+            .collect(),
+    )
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::helpers::{check_assist, check_assist_not_applicable};
+
+    use super::*;
+
+    #[test]
+    fn not_applicable_if_sorted() {
+        check_assist_not_applicable(
+            reorder_fields,
+            r#"
+        struct Foo {
+            foo: i32,
+            bar: i32,
+        }
+
+        const test: Foo = <|>Foo { foo: 0, bar: 0 };
+        "#,
+        )
+    }
+
+    #[test]
+    fn trivial_empty_fields() {
+        check_assist_not_applicable(
+            reorder_fields,
+            r#"
+        struct Foo {};
+        const test: Foo = <|>Foo {}
+        "#,
+        )
+    }
+
+    #[test]
+    fn reorder_struct_fields() {
+        check_assist(
+            reorder_fields,
+            r#"
+        struct Foo {foo: i32, bar: i32};
+        const test: Foo = <|>Foo {bar: 0, foo: 1}
+        "#,
+            r#"
+        struct Foo {foo: i32, bar: i32};
+        const test: Foo = <|>Foo {foo: 1, bar: 0}
+        "#,
+        )
+    }
+
+    #[test]
+    fn reorder_struct_pattern() {
+        check_assist(
+            reorder_fields,
+            r#"
+        struct Foo { foo: i64, bar: i64, baz: i64 }
+
+        fn f(f: Foo) -> {
+            match f {
+                <|>Foo { baz: 0, ref mut bar, .. } => (),
+                _ => ()
+            }
+        }
+        "#,
+            r#"
+        struct Foo { foo: i64, bar: i64, baz: i64 }
+
+        fn f(f: Foo) -> {
+            match f {
+                <|>Foo { ref mut bar, baz: 0, .. } => (),
+                _ => ()
+            }
+        }
+        "#,
+        )
+    }
+
+    #[test]
+    fn reorder_with_extra_field() {
+        check_assist(
+            reorder_fields,
+            r#"
+            struct Foo {
+                foo: String,
+                bar: String,
+            }
+
+            impl Foo {
+                fn new() -> Foo {
+                    let foo = String::new();
+                    <|>Foo {
+                        bar: foo.clone(),
+                        extra: "Extra field",
+                        foo,
+                    }
+                }
+            }
+            "#,
+            r#"
+            struct Foo {
+                foo: String,
+                bar: String,
+            }
+
+            impl Foo {
+                fn new() -> Foo {
+                    let foo = String::new();
+                    <|>Foo {
+                        foo,
+                        bar: foo.clone(),
+                        extra: "Extra field",
+                    }
+                }
+            }
+            "#,
+        )
+    }
+}
diff --git a/crates/ra_assists/src/lib.rs b/crates/ra_assists/src/lib.rs
index 5ba5254fd..a00136da1 100644
--- a/crates/ra_assists/src/lib.rs
+++ b/crates/ra_assists/src/lib.rs
@@ -129,6 +129,7 @@ mod handlers {
     mod replace_unwrap_with_match;
     mod split_import;
     mod add_from_impl_for_enum;
+    mod reorder_fields;
 
     pub(crate) fn all() -> &'static [AssistHandler] {
         &[
@@ -170,6 +171,7 @@ mod handlers {
             // These are manually sorted for better priorities
             add_missing_impl_members::add_missing_impl_members,
             add_missing_impl_members::add_missing_default_members,
+            reorder_fields::reorder_fields,
         ]
     }
 }