in src/lint/linter/xhpast/rules/ArcanistUndeclaredVariableXHPASTLinterRule.php [12:371]
public function process(XHPASTNode $root) {
// These things declare variables in a function:
// Explicit parameters
// Assignment
// Assignment via list()
// Static
// Global
// Lexical vars
// Builtins ($this)
// foreach()
// catch
//
// These things make lexical scope unknowable:
// Use of extract()
// Assignment to variable variables ($$x)
// Global with variable variables
//
// These things don't count as "using" a variable:
// isset()
// empty()
// Static class variables
//
// The general approach here is to find each function/method declaration,
// then:
//
// 1. Identify all the variable declarations, and where they first occur
// in the function/method declaration.
// 2. Identify all the uses that don't really count (as above).
// 3. Everything else must be a use of a variable.
// 4. For each variable, check if any uses occur before the declaration
// and warn about them.
//
// We also keep track of where lexical scope becomes unknowable (e.g.,
// because the function calls extract() or uses dynamic variables,
// preventing us from keeping track of which variables are defined) so we
// can stop issuing warnings after that.
//
// TODO: Support functions defined inside other functions which is commonly
// used with anonymous functions.
//
// TODO: parse_str() also makes lexical scope unknowable, see D13857.
$defs = $root->selectDescendantsOfTypes(array(
'n_FUNCTION_DECLARATION',
'n_METHOD_DECLARATION',
));
foreach ($defs as $def) {
// We keep track of the first offset where scope becomes unknowable, and
// silence any warnings after that. Default it to INT_MAX so we can min()
// it later to keep track of the first problem we encounter.
$scope_destroyed_at = PHP_INT_MAX;
$declarations = array(
'$this' => 0,
) + array_fill_keys($this->getSuperGlobalNames(), 0);
$declaration_tokens = array();
$exclude_tokens = array();
$exclude_strings = array();
$vars = array();
// First up, find all the different kinds of declarations, as explained
// above. Put the tokens into the $vars array.
$param_list = $def->getChildOfType(3, 'n_DECLARATION_PARAMETER_LIST');
$param_vars = $param_list->selectDescendantsOfType('n_VARIABLE');
foreach ($param_vars as $var) {
$vars[] = $var;
}
// This is PHP5.3 closure syntax: function () use ($x) {};
$lexical_vars = $def
->getChildByIndex(4)
->selectDescendantsOfType('n_VARIABLE');
foreach ($lexical_vars as $var) {
$vars[] = $var;
}
$body = $def->getChildByIndex(6);
if ($body->getTypeName() === 'n_EMPTY') {
// Abstract method declaration.
continue;
}
$static_vars = $body
->selectDescendantsOfType('n_STATIC_DECLARATION')
->selectDescendantsOfType('n_VARIABLE');
foreach ($static_vars as $var) {
$vars[] = $var;
}
$global_vars = $body
->selectDescendantsOfType('n_GLOBAL_DECLARATION_LIST');
foreach ($global_vars as $var_list) {
foreach ($var_list->getChildren() as $var) {
if ($var->getTypeName() === 'n_VARIABLE') {
$vars[] = $var;
} else {
// Dynamic global variable, i.e. "global $$x;".
$scope_destroyed_at = min($scope_destroyed_at, $var->getOffset());
// An error is raised elsewhere, no need to raise here.
}
}
}
// Include "catch (Exception $ex)", but not variables in the body of the
// catch block.
$catches = $body->selectDescendantsOfType('n_CATCH');
foreach ($catches as $catch) {
$vars[] = $catch->getChildOfType(1, 'n_VARIABLE');
}
$binary = $body->selectDescendantsOfType('n_BINARY_EXPRESSION');
foreach ($binary as $expr) {
if ($expr->getChildByIndex(1)->getConcreteString() !== '=') {
continue;
}
$lval = $expr->getChildByIndex(0);
if ($lval->getTypeName() === 'n_VARIABLE') {
$vars[] = $lval;
} else if ($lval->getTypeName() === 'n_LIST') {
// Recursively grab everything out of list(), since the grammar
// permits list() to be nested. Also note that list() is ONLY valid
// as an lval assignments, so we could safely lift this out of the
// n_BINARY_EXPRESSION branch.
$assign_vars = $lval->selectDescendantsOfType('n_VARIABLE');
foreach ($assign_vars as $var) {
$vars[] = $var;
}
}
if ($lval->getTypeName() === 'n_VARIABLE_VARIABLE') {
$scope_destroyed_at = min($scope_destroyed_at, $lval->getOffset());
// No need to raise here since we raise an error elsewhere.
}
}
$calls = $body->selectDescendantsOfType('n_FUNCTION_CALL');
foreach ($calls as $call) {
$name = strtolower($call->getChildByIndex(0)->getConcreteString());
if ($name === 'empty' || $name === 'isset') {
$params = $call
->getChildOfType(1, 'n_CALL_PARAMETER_LIST')
->selectDescendantsOfType('n_VARIABLE');
foreach ($params as $var) {
$exclude_tokens[$var->getID()] = true;
}
continue;
}
if ($name !== 'extract') {
continue;
}
$scope_destroyed_at = min($scope_destroyed_at, $call->getOffset());
}
$func_decls = $body->selectDescendantsOfType('n_FUNCTION_DECLARATION');
foreach ($func_decls as $func_decl) {
if ($func_decl->getChildByIndex(2)->getTypeName() != 'n_EMPTY') {
continue;
}
foreach ($func_decl->selectDescendantsOfType('n_VARIABLE') as $var) {
$exclude_tokens[$var->getID()] = true;
}
foreach (array('n_STRING_SCALAR', 'n_HEREDOC') as $type) {
foreach ($func_decl->selectDescendantsOfType($type) as $string) {
$exclude_strings[$string->getID()] = array();
foreach ($string->getStringVariables() as $offset => $var) {
$exclude_strings[$string->getID()][$var] = true;
}
}
}
}
// Now we have every declaration except foreach(), handled below. Build
// two maps, one which just keeps track of which tokens are part of
// declarations ($declaration_tokens) and one which has the first offset
// where a variable is declared ($declarations).
foreach ($vars as $var) {
$concrete = $this->getConcreteVariableString($var);
$declarations[$concrete] = min(
idx($declarations, $concrete, PHP_INT_MAX),
$var->getOffset());
$declaration_tokens[$var->getID()] = true;
}
// Excluded tokens are ones we don't "count" as being used, described
// above. Put them into $exclude_tokens.
$class_statics = $body
->selectDescendantsOfType('n_CLASS_STATIC_ACCESS');
$class_static_vars = $class_statics
->selectDescendantsOfType('n_VARIABLE');
foreach ($class_static_vars as $var) {
$exclude_tokens[$var->getID()] = true;
}
// Find all the variables in scope, and figure out where they are used.
// We want to find foreach() iterators which are both declared before and
// used after the foreach() loop.
$uses = array();
$all_vars = $body->selectDescendantsOfType('n_VARIABLE');
$all = array();
// NOTE: $all_vars is not a real array so we can't unset() it.
foreach ($all_vars as $var) {
// Be strict since it's easier; we don't let you reuse an iterator you
// declared before a loop after the loop, even if you're just assigning
// to it.
$concrete = $this->getConcreteVariableString($var);
$uses[$concrete][$var->getID()] = $var->getOffset();
if (isset($declaration_tokens[$var->getID()])) {
// We know this is part of a declaration, so it's fine.
continue;
}
if (isset($exclude_tokens[$var->getID()])) {
// We know this is part of isset() or similar, so it's fine.
continue;
}
$all[$var->getOffset()] = $concrete;
}
// Do foreach() last, we want to handle implicit redeclaration of a
// variable already in scope since this probably means we're ovewriting a
// local.
// NOTE: Processing foreach expressions in order allows programs which
// reuse iterator variables in other foreach() loops -- this is fine. We
// have a separate warning to prevent nested loops from reusing the same
// iterators.
$foreaches = $body->selectDescendantsOfType('n_FOREACH');
$all_foreach_vars = array();
foreach ($foreaches as $foreach) {
$foreach_expr = $foreach->getChildOfType(0, 'n_FOREACH_EXPRESSION');
$foreach_vars = array();
// Determine the end of the foreach() loop.
$foreach_tokens = $foreach->getTokens();
$last_token = end($foreach_tokens);
$foreach_end = $last_token->getOffset();
$key_var = $foreach_expr->getChildByIndex(1);
if ($key_var->getTypeName() === 'n_VARIABLE') {
$foreach_vars[] = $key_var;
}
$value_var = $foreach_expr->getChildByIndex(2);
if ($value_var->getTypeName() === 'n_VARIABLE') {
$foreach_vars[] = $value_var;
} else {
// The root-level token may be a reference, as in:
// foreach ($a as $b => &$c) { ... }
// Reach into the n_VARIABLE_REFERENCE node to grab the n_VARIABLE
// node.
$var = $value_var->getChildByIndex(0);
if ($var->getTypeName() === 'n_VARIABLE_VARIABLE') {
$var = $var->getChildByIndex(0);
}
$foreach_vars[] = $var;
}
// Remove all uses of the iterators inside of the foreach() loop from
// the $uses map.
foreach ($foreach_vars as $var) {
$concrete = $this->getConcreteVariableString($var);
$offset = $var->getOffset();
foreach ($uses[$concrete] as $id => $use_offset) {
if (($use_offset >= $offset) && ($use_offset < $foreach_end)) {
unset($uses[$concrete][$id]);
}
}
$all_foreach_vars[] = $var;
}
}
foreach ($all_foreach_vars as $var) {
$concrete = $this->getConcreteVariableString($var);
$offset = $var->getOffset();
// This is a declaration, exclude it from the "declare variables prior
// to use" check below.
unset($all[$var->getOffset()]);
$vars[] = $var;
}
// Now rebuild declarations to include foreach().
foreach ($vars as $var) {
$concrete = $this->getConcreteVariableString($var);
$declarations[$concrete] = min(
idx($declarations, $concrete, PHP_INT_MAX),
$var->getOffset());
$declaration_tokens[$var->getID()] = true;
}
foreach (array('n_STRING_SCALAR', 'n_HEREDOC') as $type) {
foreach ($body->selectDescendantsOfType($type) as $string) {
foreach ($string->getStringVariables() as $offset => $var) {
if (isset($exclude_strings[$string->getID()][$var])) {
continue;
}
$all[$string->getOffset() + $offset - 1] = '$'.$var;
}
}
}
// Issue a warning for every variable token, unless it appears in a
// declaration, we know about a prior declaration, we have explicitly
// excluded it, or scope has been made unknowable before it appears.
$issued_warnings = array();
foreach ($all as $offset => $concrete) {
if ($offset >= $scope_destroyed_at) {
// This appears after an extract() or $$var so we have no idea
// whether it's legitimate or not. We raised a harshly-worded warning
// when scope was made unknowable, so just ignore anything we can't
// figure out.
continue;
}
if ($offset >= idx($declarations, $concrete, PHP_INT_MAX)) {
// The use appears after the variable is declared, so it's fine.
continue;
}
if (!empty($issued_warnings[$concrete])) {
// We've already issued a warning for this variable so we don't need
// to issue another one.
continue;
}
$this->raiseLintAtOffset(
$offset,
pht(
'Declare variables prior to use (even if you are passing them '.
'as reference parameters). You may have misspelled this '.
'variable name.'),
$concrete);
$issued_warnings[$concrete] = true;
}
}
}