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RedundantAssignmentPlugin.php
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RedundantAssignmentPlugin.php
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<?php
declare(strict_types=1);
use ast\Node;
use Phan\AST\UnionTypeVisitor;
use Phan\Config;
use Phan\Language\Context;
use Phan\Language\Element\PassByReferenceVariable;
use Phan\Parse\ParseVisitor;
use Phan\PluginV3;
use Phan\PluginV3\PluginAwarePreAnalysisVisitor;
use Phan\PluginV3\PreAnalyzeNodeCapability;
/**
* This plugin checks for assignments where the variable already
* has the given value.
*
* - E.g. `$result = false; if (cond()) { $result = false; }`
*
* This file demonstrates plugins for Phan. Plugins hook into various events.
* DuplicateExpressionPlugin hooks into two events:
*
* - getPreAnalyzeNodeVisitorClassName
* This method returns a visitor that is called on every AST node from every
* file being analyzed in pre-order
*
* A plugin file must
*
* - Contain a class that inherits from \Phan\PluginV3
*
* - End by returning an instance of that class.
*
* It is assumed without being checked that plugins aren't
* mangling state within the passed code base or context.
*
* Note: When adding new plugins,
* add them to the corresponding section of README.md
*/
class RedundantAssignmentPlugin extends PluginV3 implements
PreAnalyzeNodeCapability
{
/**
* @return class-string - name of PluginAwarePreAnalysisVisitor subclass
*/
public static function getPreAnalyzeNodeVisitorClassName(): string
{
return RedundantAssignmentPreAnalysisVisitor::class;
}
}
/**
* This visitor analyzes node kinds that can be the root of expressions
* containing duplicate expressions, and is called on nodes in post-order.
*/
class RedundantAssignmentPreAnalysisVisitor extends PluginAwarePreAnalysisVisitor
{
/**
* @param Node $node
* An assignment operation node to analyze
* @override
*/
public function visitAssign(Node $node): void
{
$var = $node->children['var'];
if (!$var instanceof Node) {
return;
}
if ($var->kind !== ast\AST_VAR) {
return;
}
$var_name = $var->children['name'];
if (!is_string($var_name)) {
return;
}
$variable = $this->context->getScope()->getVariableByNameOrNull($var_name);
if (!$variable || $variable instanceof PassByReferenceVariable) {
return;
}
$variable_type = $variable->getUnionType();
if ($variable_type->isPossiblyUndefined() || count($variable_type->getRealTypeSet()) !== 1) {
return;
}
$old_value = $variable_type->getRealUnionType()->asValueOrNullOrSelf();
if (is_object($old_value)) {
return;
}
$expr = $node->children['expr'];
if (!ParseVisitor::isConstExpr($expr, ParseVisitor::CONSTANT_EXPRESSION_FORBID_NEW_EXPRESSION)) {
return;
}
try {
$expr_type = UnionTypeVisitor::unionTypeFromNode($this->code_base, $this->context, $expr, false);
} catch (Exception $_) {
return;
}
if (count($expr_type->getRealTypeSet()) !== 1) {
return;
}
$expr_value = $expr_type->getRealUnionType()->asValueOrNullOrSelf();
if ($expr_value !== $old_value) {
return;
}
if ($this->context->hasSuppressIssue($this->code_base, 'PhanPluginRedundantAssignment')) {
// Suppressing this suppresses the more specific issues.
return;
}
if ($this->context->isInGlobalScope()) {
if ($variable->getFileRef()->getFile() !== $this->context->getFile()) {
// Don't warn if this variable was set by a different file
return;
}
if (Config::getValue('__analyze_twice') && $variable->getFileRef()->getLineNumberStart() === $this->context->getLineNumberStart()) {
// Don't warn if this variable was set by a different file
return;
}
$issue_name = 'PhanPluginRedundantAssignmentInGlobalScope';
} elseif ($this->context->isInLoop()) {
$issue_name = 'PhanPluginRedundantAssignmentInLoop';
} else {
$issue_name = 'PhanPluginRedundantAssignment';
}
if ($this->context->isInLoop()) {
$this->context->deferCheckToOutermostLoop(function (Context $context_after_loop) use ($issue_name, $var_name, $variable_type, $var): void {
$new_variable = $context_after_loop->getScope()->getVariableByNameOrNull($var_name);
if (!$new_variable) {
return;
}
$new_variable_type = $new_variable->getUnionType();
if ($new_variable_type->isPossiblyUndefined()) {
return;
}
if ($new_variable_type->getRealTypeSet() !== $variable_type->getRealTypeSet()) {
return;
}
$this->emitPluginIssue(
$this->code_base,
(clone $this->context)->withLineNumberStart($var->lineno),
$issue_name,
'Assigning {TYPE} to variable ${VARIABLE} which already has that value',
[$variable_type, $var_name]
);
});
return;
}
$this->emitPluginIssue(
$this->code_base,
(clone $this->context)->withLineNumberStart($var->lineno),
$issue_name,
'Assigning {TYPE} to variable ${VARIABLE} which already has that value',
[$expr_type, $var_name]
);
}
}
// Every plugin needs to return an instance of itself at the
// end of the file in which it's defined.
return new RedundantAssignmentPlugin();

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