57 lines
2.1 KiB
Plaintext
57 lines
2.1 KiB
Plaintext
Overly complicated regular expressions are hard to read and to maintain and can easily cause hard-to-find bugs. If a regex is too complicated, you should consider replacing it or parts of it with regular code or splitting it apart into multiple patterns at least.
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The complexity of a regular expression is determined as follows:
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Each of the following operators increases the complexity by an amount equal to the current nesting level and also increases the current nesting level by one for its arguments:
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* ``++|++`` - when multiple ``++|++`` operators are used together, the subsequent ones only increase the complexity by 1
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* Quantifiers (``++*++``, ``+``, ``++?++``, ``++{n,m}++``, ``++{n,}++`` or ``++{n}++``)
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* Lookahead and lookbehind assertions
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Additionally, each use of the following features increase the complexity by 1 regardless of nesting:
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* character classes
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* back references
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If a regular expression is split among multiple variables, the complexity is calculated for each variable individually, not for the whole regular expression.
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== Noncompliant Code Example
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[source,javascript]
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----
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const datePattern = /^(?:(?:31(\/|-|\.)(?:0?[13578]|1[02]))\1|(?:(?:29|30)(\/|-|\.)(?:0?[13-9]|1[0-2])\2))(?:(?:1[6-9]|[2-9]\d)?\d{2})$|^(?:29(\/|-|\.)0?2\3(?:(?:(?:1[6-9]|[2-9]\d)?(?:0[48]|[2468][048]|[13579][26])|(?:(?:16|[2468][048]|[3579][26])00))))$|^(?:0?[1-9]|1\d|2[0-8])(\/|-|\.)(?:(?:0?[1-9])|(?:1[0-2]))\4(?:(?:1[6-9]|[2-9]\d)?\d{2})$/;
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if (dateString.match(datePattern)) {
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handleDate(dateString);
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}
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----
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== Compliant Solution
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[source,javascript]
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----
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const datePattern = /^\d{1,2}([-/.])\d{1,2}\1\d{1,4}$/;
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if (dateString.match(datePattern)) {
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const dateParts = dateString.split(/[-/.]/);
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const day = parseInt(dateParts[0]);
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const month = parseInt(dateParts[1]);
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const year = parseInt(dateParts[2]);
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// Put logic to validate and process the date based on its integer parts here
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}
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----
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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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include::../message.adoc[]
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include::../parameters.adoc[]
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include::../highlighting.adoc[]
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endif::env-github,rspecator-view[]
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