d41b77b623
* DART-213 Modify rule S1161: update message details * S7055: Update description * Update rule.adoc
91 lines
2.1 KiB
Plaintext
91 lines
2.1 KiB
Plaintext
== Why is this an issue?
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In Dart, you can use wildcard names, that are names consisting on underscores only: `++_++`, `++__++`, `++___++`, ...
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Usually, wildcard names should be used to name the variable/parameter that won't be directly used but needs to be declared.
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For example, as counter in the for-loop:
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`for (var _ in [1, 2, 3]) doSomething();`
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or as a field, in the pattern:
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[source,dart]
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----
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void sayHello(Person p) {
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switch (p) {
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case (name, _):
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print('Hello, $name!');
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}
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}
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----
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In Dart 3.6 and below, it is possible to read `++_++` wildcard variables, for example, `print(_);`.
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However, such behavior has changed in Dart 3.7, making `++_++` variables non-binding and breaking the code, where those variables are used.
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[source,dart]
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----
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void sayHello(String _) {
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print('Hello, $_!'); // Compiler error in Dart 3.7 and above: _ is non-binding
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}
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----
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To avoid problems during upgrades from Dart 3.6-, it's recommended to refactor the code, to not use wildcard variables.
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=== What is the potential impact?
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Once the breaking change is introduced, you will need to update all the code using wildcard variables or parameters to be able to upgrade to the latest Dart language versions.
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== How to fix it
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If the variable/parameter are supposed to be read, then give them a proper name.
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=== Code examples
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==== Noncompliant code example
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[source,dart,diff-id=1,diff-type=noncompliant]
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----
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void sayHello(String __) {
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print('Hello, $__!'); // Noncompliant in Dart 3.6 and below
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}
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----
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==== Compliant solution
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[source,dart,diff-id=1,diff-type=compliant]
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----
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void sayHello(String name) {
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print('Hello, $name!');
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}
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----
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== Resources
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=== Documentation
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* Dart Docs - https://dart.dev/tools/linter-rules/no_wildcard_variable_uses[Dart Linter rule - no_wildcard_variable_uses]
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* Dart Docs - https://dart.dev/language/pattern-types#wildcard[wildcard pattern]
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ifdef::env-github,rspecator-view[]
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'''
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== Implementation Specification
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(visible only on this page)
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=== Message
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* The referenced identifier is a wildcard.
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=== Highlighting
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Wildcard identifier
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'''
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== Comments And Links
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(visible only on this page)
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endif::env-github,rspecator-view[]
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