fix: Preserve dotted-key ordering

Fixes toml-rs#163

crates/toml_edit/src/inline_table.rs

@@ -2,7 +2,7 @@ use std::iter::FromIterator;
 
 use crate::key::Key;
 use crate::repr::Decor;
-use crate::table::{Iter, IterMut, KeyValuePairs, TableLike};
+use crate::table::{Iter, IterMut, KeyValuePairs, TableLike, sort_values_by_position};
 use crate::{InternalString, Item, KeyMut, RawString, Table, Value};
 
 /// Type representing a TOML inline table,
@@ -75,6 +75,7 @@ impl InlineTable {
                 _ => {}
             }
         }
+        sort_values_by_position(values);
     }
 
     /// Auto formats the table.

crates/toml_edit/src/table.rs

@@ -96,6 +96,7 @@ impl Table {
                 _ => {}
             }
         }
+        sort_values_by_position(values);
     }
 
     /// Auto formats the table.
@@ -518,6 +519,18 @@ fn decorate_table(table: &mut Table) {
     }
 }
 
+pub(crate) fn sort_values_by_position<'s>(values: &mut Vec<(Vec<&'s Key>, &'s Value)>) {
+    values.sort_by(|(left_kp, _), (right_kp, _)| {
+        return match (left_kp.last().map(|x| x.position),
+                      right_kp.last().map(|x| x.position)) {
+            // first if both have Some() position, its easy
+            (Some(Some(p1)), Some(Some(p2))) => p1.cmp(&p2),
+            // if one or more do not, preserve order
+            _ => std::cmp::Ordering::Equal
+        }
+    });
+}
+
 // `key1 = value1`
 pub(crate) const DEFAULT_ROOT_DECOR: (&str, &str) = ("", "");
 pub(crate) const DEFAULT_KEY_DECOR: (&str, &str) = ("", " ");