rspec/rules/S1155/dart/rule.adoc

== Why is this an issue?

When you call `isEmpty` or `isNotEmpty`, it clearly communicates the code's intention, which is to check if the collection is empty. Using `.length == 0` for this purpose is less direct and makes the code slightly more complex.

The rule also raises issues if the comparisons don't make sense. For example, `length` is always 0 or higher, so you don't need to write the following conditions:

[source,dart]
----
void fun(List<int> myList) {
  if (myList.length >= 0) { // Noncompliant, the condition is always true
    // do something
  }

  if (myList.length < 0) { // Noncompliant, the condition is always false
    // do something
  }

}
----

=== Code examples

==== Noncompliant code example

[source,dart,diff-id=1,diff-type=noncompliant]
----
void fun(List<int> myList) {
  if (myList.length == 0) { // Noncompliant
    // do something
  }

  if (myList.length != 0) { // Noncompliant
    // do something
  }

}
----

==== Compliant solution

[source,dart,diff-id=1,diff-type=compliant]
----
void fun(List<int> myList) {
  if (myList.isEmpty) {
    // do something
  }

  if (myList.isNotEmpty) {
    // do something
  }

}
----

== Resources

* Dart Docs - https://dart.dev/tools/linter-rules/prefer_is_empty[Dart Linter rule]

ifdef::env-github,rspecator-view[]

'''
== Implementation Specification
(visible only on this page)

=== Message

* Use 'isEmpty'/'isNotEmpty' instead of 'length' to test whether the collection is 'empty'/'not empty'.
* The comparison is always 'true'/'false' because the length is always greater than or equal to 0.

=== Highlighting

The condition of the `if` statement.

'''

endif::env-github,rspecator-view[]