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Dealing with code issues

Psalm has a large number of code issues. Each project can specify its own reporting level for a given issue.

Code issue levels in Psalm fall into three categories:

error
This will cause Psalm to print a message, and to ultimately terminate with a non-zero exit status
info
This will cause Psalm to print a message
suppress
This will cause Psalm to ignore the code issue entirely

The third category, suppress, is the one you will probably be most interested in, especially when introducing Psalm to a large codebase.

Suppressing issues

There are two ways to suppress an issue – via the Psalm config or via a function docblock.

Config suppression

You can use the <issueHandlers> tag in the config file to influence how issues are treated.

Some issue types allow the use of referencedMethod and referencedClass to isolate known trouble spots.

<issueHandlers>
  <MissingPropertyType errorLevel="suppress" />

  <InvalidReturnType>
    <errorLevel type="suppress">
      <directory name="some_bad_directory" /> <!-- all InvalidReturnType issues in this directory are suppressed -->
      <file name="some_bad_file.php" />  <!-- all InvalidReturnType issues in this file are suppressed -->
    </errorLevel>
  </InvalidReturnType>
  <UndefinedMethod>
    <errorLevel type="suppress">
      <referencedMethod name="Bar\Bat::bar" />
      <file name="some_bad_file.php" />
    </errorLevel>
  </UndefinedMethod>
  <UndefinedClass>
    <errorLevel type="suppress">
      <referencedClass name="Bar\Bat\Baz" />
    </errorLevel>
  </UndefinedClass>
</issueHandlers>

Docblock suppression

You can also use @psalm-suppress IssueName on a function's docblock to suppress Psalm issues e.g.

/**
 * @psalm-suppress InvalidReturnType
 */
function (int $a) : string {
  return $a;
}

You can also suppress issues at the line level e.g.

/**
 * @psalm-suppress InvalidReturnType
 */
function (int $a) : string {
  /**
   * @psalm-suppress InvalidReturnStatement
   */
  return $a;
}