fast_immutable_collections

Releases

1. ▸▾12.0.02 Oct 2026Breaking2 sources agree

   Breaking change: IList, ISet and IMap that compare by identity (isDeepEquals: false in the constructor) now compare the collection objects themselves.…

   • Breaking change: IList, ISet and IMap that compare by identity (isDeepEquals: false in the constructor) now compare the collection objects themselves. In other words, collection1 == collection2 is now the same as identical(collection1, collection2) when deep equals is turned off. Previously, they compared their internal structure, so two different collections that shared the same internal structure were considered equal. However, this internal structure changes when a collection is flushed (which may also happen automatically, just by reading it), so their == and hashCode could change, and they could be lost in a Set or as Map keys. The hashCode of constant ones also changed each time it was read. Note: You can still use same() to check if two collections share the same internal structure. Collections that compare by deep equals (isDeepEquals: true in the constructor) are the default, and are not affected.

   • Fixed IMap.fromJson and IMap.toJson for non-String keys when used with json_serializable. IMap keys now work the same as regular Map keys, including enums (https://github.com/marcglasberg/fast_immutable_collections/issues/39), DateTime, BigInt and Uri (https://github.com/marcglasberg/fast_immutable_collections/issues/58), and custom key types with a JsonConverter or their own fromJson/toJson (https://github.com/marcglasberg/fast_immutable_collections/issues/82). For example:

     @JsonSerializable()
     class MyClass {
       final IMap<MyEnum, bool> byEnum;
       final IMap<DateTime, String> byDate;    
     }
     

     The fromJsonK function now receives the JSON key string, except when the key type is bool, int, double or num, in which case it receives the parsed value (as json_serializable expects). If the key is not a string, number, bool, DateTime, BigInt, Uri or enum, IMap.toJson now calls the key's own toJson method.

     Note: For IMap<Object, V> and IMap<dynamic, V>, fromJsonK now receives the JSON key string. Previously, the key was wrongly converted into a bool.

   • Much faster iteration (like for (final item in ilist)) of IList, ISet and IMap that were not yet flushed. Previously, each item went through the iterators of all internal nodes created by add and addAll. Now each item is read only once, using very little extra memory, and without creating any lists. For example, iterating an IList of 10,000 items after 500 add calls is now about 480 times faster, and an ISet or IMap after 50 add calls, about 9 to 45 times faster. The same is true for IMap.entries, IMap.keys and IMap.values, including maps updated with add or update of existing keys, and for methods like join, elementAt and []. For example, after 200 add calls, IList.join is about 48 times faster, and IList[] about 90 times faster.

   • Much faster flush (and unlock) of IList, ISet, IMap and IMapOfSets created by many add, addAll and update calls. These calls create a chain of internal nodes, and flushing used to iterate this chain, which was slow because each item went through the iterators of all the nodes above it. Now flushing walks down the chain only once, without iterating it. Since flushing happens automatically after a number of operations, this also makes many consecutive additions much faster. For example, adding 1000 items to an IList of 10,000 items is now about 800 times faster, and to an ISet or IMap of 10,000 items, about 12 to 20 times faster.

   • Faster where, map, any, every, forEach, fold, toList and toSet of IList and ISet (and of the keys and values of IMap) that were not yet flushed, since they no longer go through the iterators of all internal nodes. For example, where and any are now 16 to 50 times faster after 20 add calls, IList.toList is 3 to 12 times faster, and toList(growable: false) is 1.5 to 2.9 times faster.

   • ISet.toList is about 5 times faster for sets that are already flushed.

   • Fixed ISet.anyItem throwing StateError for a non-empty set created by adding items to an empty set. For example: ISet<int>([]).addAll([1]).anyItem.

   • Fixed IList.single and ISet.single returning an item, instead of throwing StateError, after adding items to a list or set with a single item. For example: IList([1]).addAll([2]).single returned 1.

   • ISet.difference and ISet.intersection are about 1.4 times faster for sets that were not yet flushed, and their results now keep the iteration order of the set.

   • Prevented the possibility of stack overflows in many methods (like length, contains, [], first, entries and iteration) of IList, ISet and IMap with a large number of unflushed operations. Note that this was only possible when ImmutableCollection.autoFlush was false.

   • Fixed ImmutableCollection.resetAllConfigurations() not resetting IList.defaultConfig, ISet.defaultConfig and IMap.defaultConfig. It now also resets IMapOfSets.defaultConfig.

   • Fixed equalItems of IList and ISet, and equalItemsToIMap of IMap, returning false for collections with equal items but different configurations, after their hashCode was calculated. Also fixed equalItemsAndConfig returning false for collections that compare by identity and have equal items and configurations, after their hashCode was calculated.

   • Fixed ISet.withConfig(iset, config) not sorting the set when config.sort is true and iset is an ISet. For example, ISet.withConfig({3, 1, 2}.lock, ConfigSet(sort: true)) returned [3, 1, 2].

   • Fixed IMap.cast() throwing a TypeError for maps that were not yet flushed (for example, after add). Now, as documented, if the map is already an IMap<RK, RV>, it's returned unchanged.

   • Fixed IMap.toValueSet(compare: ...) failing an assertion. Now it sorts the values with the given compare function.

   • Fixed IMap.unlockSorted not sorting the map when the map's ConfigMap.sort is false.

   • Fixed IMap.entryOrNull throwing for a key that exists with a null value.

   • Fixed IMapOfSets.withConfig(null, config) ignoring the given config, and IMapOfSets.removeValues and IMapOfSets.removeValuesWhere losing the map configuration (like sortKeys).

   • Fixed remove, removeAll and removeMany of constant and empty lists, remove of constant and empty sets, and remove and removeWhere of constant and empty maps, returning a new collection instead of the same instance when nothing is removed.

   • Fixed IList<Never>().addAll(...) throwing when ImmutableCollection.disallowUnsafeConstructors is true.

   • Fixed sumBy throwing UnsupportedError for empty iterables when the result type is num. For example, <num>[].sumBy((e) => e) now returns 0.

   • Fixed compareObject ignoring nullsBefore: true when comparing the keys and values of MapEntrys.

   • Fixed ListMap.map not keeping the order of the ListMap.

   • Fixed lookup of ModifiableSetFromISet and UnmodifiableSetFromISet (returned by ISet.unlockLazy and ISet.unlockView) returning the given element, instead of the element that is in the set.

   • Fixed the docs of isFirst, isNotFirst, isLast and isNotLast, which said they return null for empty iterables.