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</header> <div class="post-header"> <h1 class="post-title-main">Guidelines for standard rules</h1> </div> <div class="post-content" data-github-edit-url="https://github.com/pmd/pmd/blob/master/docs/pages/pmd/devdocs/major_contributions/rule_guidelines.md"> <div class="summary">Guidelines for rules that are included in the standard distribution</div> <details id="inline-toc-details"> <summary>Table of Contents</summary> <div id="inline-toc"><!-- empty, move TOC here when screen size too small --></div> </details> <div class="alert alert-info" role="alert"><i class="fas fa-info-circle"></i> <b>Note:</b> These guidelines are new and most rules don’t follow these guidelines yet. The goal is, that eventually all rules are updated. </div> <h2 id="why-do-we-need-these-guidelines">Why do we need these guidelines?</h2> <ul> <li>To prevent low quality contributions</li> <li>To reduce time reviewing rules</li> </ul> <p>They just apply to rules included in the standard distribution.</p> <h2 id="requirements-for-standard-rules">Requirements for standard rules</h2> <p>To be included in stock PMD, a rule needs</p> <ul> <li>Broad applicability. It may be specific to a framework, but then, this framework should be widely used</li> <li>Solid documentation. See below</li> <li>If it’s a performance rule: solid benchmarks. No micro-optimization rules</li> <li>No overlap with other rules</li> </ul> <h2 id="dosdonts-rule-rules">Dos/Don’ts (rule rules)</h2> <ul> <li>Rule naming <ul> <li><strong>Don’t</strong> put the implementation of the rule in the name, because it will be awkward if the scope of the rule changes <ul> <li>Eg. <em>SwitchStmtShouldHaveDefault</em> -> since enums are a thing they don’t necessarily need to have a default anymore, they should be exhaustive. So the rule name lies now…</li> <li>Eg. <em>MissingBreakInSwitch</em> -> it’s obvious that this is supposed to find fall-through switches. Counting breaks is not a clever way to do it, but since it’s in the name we can’t change it without renaming the rule.</li> </ul> </li> <li><strong>Do</strong> use rule names that name the underlying problem that violations exhibit <ul> <li>Eg. instead of <em>SwitchStmtShouldHaveDefault</em>, use <em>NonExhaustiveSwitchStatement</em> -> this is the problem, the description of the rule will clarify why it is a problem and how to fix it (add a default, or add branches, or something else in the future)</li> <li>Eg. instead of <em>MissingBreakInSwitch</em>, use <em>SwitchCaseFallsThrough</em></li> </ul> </li> <li><strong>Don’t</strong> create several rules for instances of the same problem <ul> <li><em>EmptyIfStmt</em> and <em>EmptyWhileStmt</em> are actually the same problem, namely, that there’s useless syntax in the tree.</li> </ul> </li> <li><strong>Don’t</strong> limit the rule name to strictly what the rule can do today <ul> <li>Eg. <em>UnusedPrivateField</em> is a bad name. The problem is that there is an unused field, not that it is private as well. If we had the ability to find unused package-private fields, we would report them too. So if one day we get that ability, using a name like <em>UnusedField</em> would allow us to keep the name.</li> </ul> </li> </ul> </li> <li>Rule messages <ul> <li><strong>Do</strong> write rule messages that neutrally point out a problem or construct that should be reviewed (“Unnecessary parentheses”)</li> <li><strong>Don’t</strong> write rule messages that give an order (“Avoid unnecessary parentheses”) especially without explaining why, like here</li> <li><strong>Don’t</strong> write rule messages that are tautological (“Unnecessary parentheses should be removed”). The answer to this would be an annoyed “yes I know, so what?”.</li> </ul> </li> <li><strong>Do</strong> use Markdown in rule descriptions and break lines at a reasonable 80 chars</li> <li><strong>Do</strong> thoroughly comment rule examples. It must be obvious where to look</li> <li><strong>Do</strong> comment your xpath expressions too</li> </ul> <h2 id="rule-description-template">Rule description template</h2> <ul> <li>What the rule reports (1 summary line)</li> <li>Why the rule exists and where it might be useful (including, since which language version, etc)</li> <li>Blank line</li> <li>Explain all assumptions that the rule makes and keywords used in the previous paragraph. (“overridden methods are ignored”, “for the purposes of this rule, a ‘visible’ field is non-private”).</li> <li>Describe known limitations if any</li> <li>Blank line</li> <li>For each property, explain how it modifies the assumptions and why you would want to use it. <strong>If you can’t explain why it’s there then it shouldn’t be there!</strong></li> </ul> <div class="tags"> <b>Tags: </b> <a href="tag_devdocs.html" class="btn btn-outline-secondary navbar-btn cursorNorm" role="button">devdocs</a> <a href="tag_extending.html" class="btn btn-outline-secondary navbar-btn cursorNorm" role="button">extending</a> </div> </div> <footer> <hr /> <div> This documentation is written in markdown. <br /> If there is something missing or can be improved, edit this page on github and create a PR: <a target="_blank" href="https://github.com/pmd/pmd/blob/master/docs/pages/pmd/devdocs/major_contributions/rule_guidelines.md" role="button" ><i class="fab fa-github fa-lg"></i> Edit on GitHub</a > </div> <hr /> <div class="row"> <div class="col-lg-12 footer"> ©2024 PMD Open Source Project. 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