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var U = require("./node");
var MAP = U.MAP;
var run_code = require("./sandbox").run_code;
// Reduce a ufuzz-style `console.log` based test case by iteratively replacing
// AST nodes with various permutations. Each AST_Statement in the tree is also
// speculatively dropped to determine whether it is needed. If the altered
// tree and the last known good tree produce the same non-nil error-free output
// after being run, then the permutation survives to the next generation and
// is the basis for subsequent iterations. The test case is reduced as a
// consequence of complex expressions being replaced with simpler ones.
// This function assumes that the testcase will not result in a parse or
// runtime Error. Note that a reduced test case will have different runtime
// output - it is not functionally equivalent to the original. The only criteria
// is that once the generated reduced test case is run without minification, it
// will produce different output from the code minified with `minify_options`.
// Returns a `minify` result object with an additonal boolean property `reduced`.
module.exports = function reduce_test(testcase, minify_options, reduce_options) {
minify_options = minify_options || { compress: {}, mangle: false };
reduce_options = reduce_options || {};
var timeout = 1500; // start with a low timeout
var max_iterations = reduce_options.max_iterations || 1000;
var verbose = reduce_options.verbose;
var minify_options_json = JSON.stringify(minify_options);
var reduced = false;
if (testcase instanceof U.AST_Node) testcase = testcase.print_to_string();
// the initial timeout to assess the viability of the test case must be large
if (producesDifferentResultWhenMinified(testcase, minify_options, 5000)) {
// Replace expressions with constants that will be parsed into
// AST_Nodes as required. Each AST_Node has its own permutation count,
// so these replacements can't be shared.
// Although simpler replacements are generally faster and better,
// feel free to experiment with a different replacement set.
var REPLACEMENTS = [
// "null", "''", "false", "'foo'", "undefined", "9",
"1", "0",
];
// There's a relationship between each node's _permute counter and
// REPLACEMENTS.length which is why fractional _permutes were needed.
// One could scale all _permute operations by a factor of `steps`
// to only deal with integer operations, but this works well enough.
var steps = 4; // must be a power of 2
var step = 1 / steps; // 0.25 is exactly representable in floating point
var tt = new U.TreeTransformer(function(node, descend, in_list) {
if (CHANGED) return;
// quick ignores
if (node instanceof U.AST_Toplevel) return;
if (node instanceof U.AST_Accessor) return;
if (node instanceof U.AST_Directive) return;
// if (node instanceof U.AST_Var) return;
// if (node instanceof U.AST_VarDef) return;
var parent = tt.parent();
// ignore call expressions
if (parent instanceof U.AST_Call && parent.expression === node) return;
// ensure that the _permute prop is a number.
// can not use `node.start._permute |= 0;` as it will erase fractional part.
if (typeof node.start._permute === "undefined") node.start._permute = 0;
// if node reached permutation limit - skip over it.
// no structural AST changes before this point.
if (node.start._permute >= REPLACEMENTS.length) return;
if (parent instanceof U.AST_Assign
&& parent.left === node
|| parent instanceof U.AST_Unary
&& parent.expression === node
&& ["++", "--", "delete"].indexOf(parent.operator) >= 0) {
// ignore lvalues
return;
}
if (parent instanceof U.AST_If && parent.alternative === node) {
// retain the if statement and drop its else block
node.start._permute++;
CHANGED = true;
return null;
}
// node specific permutations with no parent logic
if (node instanceof U.AST_Array) {
var expr = node.elements[0];
if (expr) {
node.start._permute++;
CHANGED = true;
return expr;
}
}
else if (node instanceof U.AST_Binary) {
CHANGED = true;
return [
node.left,
node.right,
][ ((node.start._permute += step) * steps | 0) % 2 ];
}
else if (node instanceof U.AST_Catch || node instanceof U.AST_Finally) {
// drop catch or finally block
node.start._permute++;
CHANGED = true;
return null;
}
else if (node instanceof U.AST_Conditional) {
CHANGED = true;
return [
node.condition,
node.consequent,
node.alternative,
][ ((node.start._permute += step) * steps | 0) % 3 ];
}
else if (node instanceof U.AST_BlockStatement) {
if (node.body.length === 1) {
node.start._permute++;
CHANGED = true;
return node.body[0]; // each child is an AST_Statement
}
}
else if (node instanceof U.AST_Call) {
if (/^console/.test(node.print_to_string())) return node;
var expr = [
node.expression,
node.args[0],
][ node.start._permute++ % 2 ];
if (expr) {
CHANGED = true;
return expr;
}
}
else if (node instanceof U.AST_DWLoop) {
var expr = [
node.condition,
node.body,
null, // intentional
][ (node.start._permute * steps | 0) % 3 ];
node.start._permute += step;
if (!expr) {
if (node.body[0] instanceof U.AST_Break) {
if (node instanceof U.AST_Do) {
CHANGED = true;
return MAP.skip;
}
expr = node.condition; // AST_While - fall through
}
}
if (expr) {
CHANGED = true;
return expr instanceof U.AST_Statement ? expr : new U.AST_SimpleStatement({
body: expr,
start: {},
});
}
}
else if (node instanceof U.AST_PropAccess) {
var expr = [
node.expression,
node.property instanceof U.AST_Node && node.property,
][ node.start._permute++ % 2 ];
if (expr) {
CHANGED = true;
return expr;
}
}
else if (node instanceof U.AST_For) {
var expr = [
node.init,
node.condition,
node.step,
node.body,
][ (node.start._permute * steps | 0) % 4 ];
node.start._permute += step;
if (expr) {
CHANGED = true;
return expr instanceof U.AST_Statement ? expr : new U.AST_SimpleStatement({
body: expr,
start: {},
});
}
}
else if (node instanceof U.AST_ForIn) {
var expr = [
node.init,
node.object,
node.body,
][ (node.start._permute * steps | 0) % 3 ];
node.start._permute += step;
if (expr) {
CHANGED = true;
return expr instanceof U.AST_Statement ? expr : new U.AST_SimpleStatement({
body: expr,
start: {},
});
}
}
else if (node instanceof U.AST_If) {
var body = [
node.body,
node.alternative,
][ (node.start._permute++) % 2 ];
if (body) {
// replace if statement with its then block or the else block
CHANGED = true;
return body;
}
}
else if (node instanceof U.AST_Object) {
// first property's value
var expr = node.properties[0] instanceof U.AST_ObjectKeyVal && node.properties[0].value;
if (expr) {
node.start._permute++;
CHANGED = true;
return expr;
}
}
else if (node instanceof U.AST_Switch) {
var expr = [
node.expression, // switch expression
node.body[0] && node.body[0].expression, // first case expression or undefined
node.body[0] && node.body[0].body[0], // first case body statement or undefined
][ (node.start._permute * steps | 0) % 3 ];
node.start._permute += step;
if (expr) {
CHANGED = true;
return expr instanceof U.AST_Statement ? expr : new U.AST_SimpleStatement({
body: expr,
start: {},
});
}
}
else if (node instanceof U.AST_Try) {
var body = [
node.body,
node.bcatch && node.bcatch.body,
node.bfinally && node.bfinally.body,
null, // intentional
][ (node.start._permute * steps | 0) % 4 ];
node.start._permute += step;
if (body) {
// replace try statement with try block, catch block, or finally block
CHANGED = true;
return new U.AST_BlockStatement({
body: body,
start: {},
});
} else {
// replace try with a break or return if first in try statement
if (node.body[0] instanceof U.AST_Break
|| node.body[0] instanceof U.AST_Return) {
CHANGED = true;
return node.body[0];
}
}
}
else if (node instanceof U.AST_Unary) {
node.start._permute++;
CHANGED = true;
return node.expression;
}
if (in_list) {
// special case to drop object properties and switch branches
if (parent instanceof U.AST_Object
|| parent instanceof U.AST_Switch && parent.expression != node) {
node.start._permute++;
CHANGED = true;
return MAP.skip;
}
// replace or skip statement
if (node instanceof U.AST_Statement) {
if (node instanceof U.AST_BlockStatement
&& ( parent instanceof U.AST_IterationStatement
|| parent instanceof U.AST_Switch)) {
// don't drop the block of a switch or loop
return;
}
if (node instanceof U.AST_LabeledStatement) {
if (node.body instanceof U.AST_Statement) {
// replace labelled statement with its non-labelled body
node.start._permute = REPLACEMENTS.length;
CHANGED = true;
return node.body;
}
}
node.start._permute++;
CHANGED = true;
return MAP.skip;
}
}
// replace or remove this node depending on whether it's in a list
var newNode = new U.parse(REPLACEMENTS[node.start._permute % REPLACEMENTS.length | 0], {
expression: true,
});
newNode.start._permute = ++node.start._permute;
CHANGED = true;
return in_list ? MAP.skip : newNode;
});
for (var pass = 1; pass <= 3; ++pass) {
var testcase_ast = U.parse(testcase);
testcase_ast.walk(new U.TreeWalker(function(node) {
// unshare start props to retain visit data between iterations
node.start = JSON.parse(JSON.stringify(node.start));
node.start._permute = 0;
}));
for (var c = 0; c < max_iterations; ++c) {
if (verbose) {
if (pass == 1 && c % 25 == 0) {
console.error("// reduce test pass "
+ pass + ", iteration " + c + ": " + testcase.length + " bytes");
}
}
var CHANGED = false;
var code_ast = testcase_ast.clone(true).transform(tt);
if (!CHANGED) break;
try {
var code = code_ast.print_to_string();
} catch (ex) {
// AST is not well formed.
// no harm done - just log the error, ignore latest change and continue iterating.
console.error("*** Error generating code from AST.");
console.error(ex.stack);
console.error("*** Discarding permutation and continuing.");
}
if (code) {
var differs = producesDifferentResultWhenMinified(code, minify_options, timeout);
if (differs) {
if (differs.timed_out) {
// can't trust the validity of `code_ast` and `code` when timed out.
// no harm done - just ignore latest change and continue iterating.
if (timeout < 5000) timeout += 100;
} else {
// latest permutation is valid, so use it as the basis of new changes
testcase_ast = code_ast;
testcase = code;
var testcase_unminified_result = differs.unminified_result;
var testcase_minified_result = differs.minified_result;
}
}
}
}
if (c == 0) break;
if (verbose) {
console.error("// reduce test pass " + pass + ": " + testcase.length + " bytes");
}
}
reduced = true;
testcase += "\n// output: " + testcase_unminified_result
+ "\n// minify: " + testcase_minified_result
+ "\n// options: " + minify_options_json;
} else {
// same stdout result produced when minified
testcase = "// Can't reproduce test failure with minify options provided:"
+ "\n// " + minify_options_json;
}
var result = U.minify(testcase, {
compress: false,
mangle: false,
output: {
beautify: true,
braces: true,
comments: true,
}
});
result.reduced = reduced;
return result;
};
function producesDifferentResultWhenMinified(code, minify_options, timeout) {
var toplevel = undefined;
var unminified_result = run_code(code, toplevel, timeout);
if (/timed out/i.test(unminified_result)) return false;
if (/^\s*$|Error/.test(unminified_result)) return false;
var minified_result = run_code(U.minify(code, minify_options).code, toplevel, timeout);
if (/timed out/i.test(minified_result)) return { timed_out: true };
if (/^\s*$/.test(minified_result)) return false;
return unminified_result !== minified_result ? {
unminified_result: unminified_result,
minified_result: minified_result,
} : false;
}
Error.stackTraceLimit = Infinity;
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