var crypto = require("crypto");
var U = require("..");
var List = U.List;
var os = require("os");
var sandbox = require("./sandbox");
// Reduce a 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 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. 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.
Error.stackTraceLimit = Infinity;
module.exports = function reduce_test(testcase, minify_options, reduce_options) {
minify_options = minify_options || {};
reduce_options = reduce_options || {};
var print_options = {};
[
"ie",
"v8",
"webkit",
].forEach(function(name) {
var value = minify_options[name] || minify_options.output && minify_options.output[name];
if (value) print_options[name] = value;
});
if (testcase instanceof U.AST_Node) testcase = testcase.print_to_string(print_options);
var max_iterations = reduce_options.max_iterations || 1000;
var max_timeout = reduce_options.max_timeout || 10000;
var warnings = [];
var log = reduce_options.log || function(msg) {
warnings.push(msg);
};
var verbose = reduce_options.verbose;
var minify_options_json = JSON.stringify(minify_options, null, 2);
var result_cache = Object.create(null);
var test_for_diff = compare_run_code;
// the initial timeout to assess the viability of the test case must be large
var differs = test_for_diff(testcase, minify_options, result_cache, max_timeout);
if (verbose) {
log("// Node.js " + process.version + " on " + os.platform() + " " + os.arch());
}
if (differs && differs.error && [ "DefaultsError", "SyntaxError" ].indexOf(differs.error.name) < 0) {
test_for_diff = test_minify;
differs = test_for_diff(testcase, minify_options, result_cache, max_timeout);
}
if (!differs) {
// same stdout result produced when minified
return {
code: [
"// Can't reproduce test failure",
"// minify options: " + to_comment(minify_options_json)
].join("\n"),
warnings: warnings,
};
} else if (differs.timed_out) {
return {
code: [
"// Can't reproduce test failure within " + max_timeout + "ms",
"// minify options: " + to_comment(minify_options_json)
].join("\n"),
warnings: warnings,
};
} else if (differs.error) {
differs.warnings = warnings;
return differs;
} else if (sandbox.is_error(differs.unminified_result)
&& sandbox.is_error(differs.minified_result)
&& differs.unminified_result.name == differs.minified_result.name) {
return {
code: [
"// No differences except in error message",
"// minify options: " + to_comment(minify_options_json)
].join("\n"),
warnings: warnings,
};
} else {
max_timeout = Math.min(100 * differs.elapsed, max_timeout);
// 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_Accessor) return;
if (node instanceof U.AST_Directive) return;
if (!in_list && node instanceof U.AST_EmptyStatement) return;
if (node instanceof U.AST_Label) return;
if (node instanceof U.AST_LabelRef) return;
if (node instanceof U.AST_Toplevel) return;
var parent = tt.parent();
if (node instanceof U.AST_SymbolFunarg && parent instanceof U.AST_Accessor) return;
if (!in_list && parent.rest !== node && node instanceof U.AST_SymbolDeclaration) 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;
// ignore lvalues
if (parent instanceof U.AST_Assign && parent.left === node) return;
if (parent instanceof U.AST_DefaultValue && parent.name === node) return;
if (parent instanceof U.AST_DestructuredKeyVal && parent.value === node) return;
if (parent instanceof U.AST_Unary && parent.expression === node) switch (parent.operator) {
case "++":
case "--":
case "delete":
return;
}
if (parent instanceof U.AST_VarDef && parent.name === node) return;
// preserve class methods
if (parent instanceof U.AST_ClassMethod && parent.value === node) return;
// preserve exports
if (parent instanceof U.AST_ExportDeclaration) return;
if (parent instanceof U.AST_ExportDefault) return;
if (parent instanceof U.AST_ExportForeign) return;
if (parent instanceof U.AST_ExportReferences) return;
// preserve sole definition of an export statement
if (node instanceof U.AST_VarDef
&& parent.definitions.length == 1
&& tt.parent(1) instanceof U.AST_ExportDeclaration) {
return;
}
// preserve for (var xxx; ...)
if (parent instanceof U.AST_For && parent.init === node && node instanceof U.AST_Definitions) return node;
// preserve for (xxx in/of ...)
if (parent instanceof U.AST_ForEnumeration && parent.init === node) return node;
// preserve super(...)
if (node.TYPE == "Call" && node.expression instanceof U.AST_Super) return;
if (node instanceof U.AST_Super && parent.TYPE == "Call" && parent.expression === node) return node;
// node specific permutations with no parent logic
if (node instanceof U.AST_Array) {
var expr = node.elements[0];
if (expr && !(expr instanceof U.AST_Hole)) {
node.start._permute++;
CHANGED = true;
return expr instanceof U.AST_Spread ? expr.expression : expr;
}
}
else if (node instanceof U.AST_Binary) {
var permute = ((node.start._permute += step) * steps | 0) % 4;
var expr = [
node.left,
node.right,
][ permute & 1 ];
if (expr instanceof U.AST_Destructured) expr = expr.transform(new U.TreeTransformer(function(node, descend) {
if (node instanceof U.AST_DefaultValue) return new U.AST_Assign({
operator: "=",
left: node.name.transform(this),
right: node.value,
start: {},
});
if (node instanceof U.AST_DestructuredKeyVal) return new U.AST_ObjectKeyVal(node);
if (node instanceof U.AST_Destructured) {
node = new (node instanceof U.AST_DestructuredArray ? U.AST_Array : U.AST_Object)(node);
descend(node, this);
}
return node;
}));
CHANGED = true;
return permute < 2 ? expr : wrap_with_console_log(expr);
}
else if (node instanceof U.AST_BlockStatement) {
if (in_list && node.body.filter(function(node) {
return node instanceof U.AST_Const;
}).length == 0) {
node.start._permute++;
CHANGED = true;
return List.splice(node.body);
}
}
else if (node instanceof U.AST_Call) {
var expr = [
!(node.expression instanceof U.AST_Super) && node.expression,
node.args[0],
null, // intentional
][ ((node.start._permute += step) * steps | 0) % 3 ];
if (expr) {
CHANGED = true;
return expr instanceof U.AST_Spread ? expr.expression : expr;
}
if (node.expression instanceof U.AST_Arrow && node.expression.value) {
var seq = node.args.slice();
seq.push(node.expression.value);
CHANGED = true;
return to_sequence(seq);
}
if (node.expression instanceof U.AST_Function) {
// hoist and return expressions from the IIFE function expression
var seq = [];
node.expression.body.forEach(function(node) {
var expr = expr instanceof U.AST_Exit ? node.value : node.body;
if (expr instanceof U.AST_Node && !U.is_statement(expr) && can_hoist(expr)) {
// collect expressions from each statements' body
seq.push(expr);
}
});
CHANGED = true;
return to_sequence(seq);
}
}
else if (node instanceof U.AST_Catch) {
// drop catch 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_DefaultValue) {
node.start._permute++;
CHANGED = true;
return node.name;
}
else if (node instanceof U.AST_DestructuredArray) {
var expr = node.elements[0];
if (expr && !(expr instanceof U.AST_Hole)) {
node.start._permute++;
CHANGED = true;
return expr;
}
}
else if (node instanceof U.AST_DestructuredObject) {
// first property's value
var expr = node.properties[0];
if (expr) {
node.start._permute++;
CHANGED = true;
return expr.value;
}
}
else if (node instanceof U.AST_Defun) {
switch (((node.start._permute += step) * steps | 0) % 2) {
case 0:
CHANGED = true;
return List.skip;
default:
if (!has_exit(node) && can_hoist(node)) {
// hoist function declaration body
var body = node.body;
node.body = [];
body.push(node); // retain function with empty body to be dropped later
CHANGED = true;
return List.splice(body);
}
}
}
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 List.skip;
}
expr = node.condition; // AST_While - fall through
}
}
if (expr && (expr !== node.body || !has_loopcontrol(expr, node, parent))) {
CHANGED = true;
return to_statement(expr);
}
}
else if (node instanceof U.AST_Finally) {
// drop finally block
node.start._permute++;
CHANGED = true;
return null;
}
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 && (expr !== node.body || !has_loopcontrol(expr, node, parent))) {
CHANGED = true;
return to_statement_init(expr);
}
}
else if (node instanceof U.AST_ForEnumeration) {
var expr;
switch ((node.start._permute * steps | 0) % 3) {
case 0:
if (node.init instanceof U.AST_Definitions) {
if (node.init instanceof U.AST_Const) break;
if (node.init.definitions[0].name instanceof U.AST_Destructured) break;
}
expr = node.init;
break;
case 1:
expr = node.object;
break;
case 2:
if (!has_loopcontrol(node.body, node, parent)) expr = node.body;
break;
}
node.start._permute += step;
if (expr) {
CHANGED = true;
return to_statement_init(expr);
}
}
else if (node instanceof U.AST_If) {
var expr = [
node.condition,
node.body,
node.alternative,
][ (node.start._permute * steps | 0) % 3 ];
node.start._permute += step;
if (expr) {
// replace if statement with its condition, then block or else block
CHANGED = true;
return to_statement(expr);
}
}
else if (node instanceof U.AST_Object) {
// first property's value
var expr = node.properties[0];
if (expr instanceof U.AST_ObjectKeyVal) {
expr = expr.value;
} else if (expr instanceof U.AST_Spread) {
expr = expr.expression;
} else if (expr && expr.key instanceof U.AST_Node) {
expr = expr.key;
} else {
expr = null;
}
if (expr) {
node.start._permute++;
CHANGED = true;
return expr;
}
}
else if (node instanceof U.AST_PropAccess) {
var expr = [
!(node.expression instanceof U.AST_Super) && node.expression,
node.property instanceof U.AST_Node && !(parent instanceof U.AST_Destructured) && node.property,
][ node.start._permute++ % 2 ];
if (expr) {
CHANGED = true;
return expr;
}
}
else if (node instanceof U.AST_SimpleStatement) {
if (node.body instanceof U.AST_Call && node.body.expression instanceof U.AST_Function) {
// hoist simple statement IIFE function expression body
node.start._permute++;
if (!has_exit(node.body.expression) && can_hoist(node.body.expression)) {
CHANGED = true;
return List.splice(node.body.expression.body);
}
}
}
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], // first case body or undefined
][ (node.start._permute * steps | 0) % 4 ];
node.start._permute += step;
if (expr && (!(expr instanceof U.AST_Statement) || !has_loopcontrol(expr, node, parent))) {
CHANGED = true;
return expr instanceof U.AST_SwitchBranch ? new U.AST_BlockStatement({
body: expr.body.slice(),
start: {},
}) : to_statement(expr);
}
}
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;
}
else if (node instanceof U.AST_Var) {
if (node.definitions.length == 1 && node.definitions[0].value) {
// first declaration value
node.start._permute++;
CHANGED = true;
return to_statement(node.definitions[0].value);
}
}
else if (node instanceof U.AST_LabeledStatement) {
if (node.body instanceof U.AST_Statement
&& !has_loopcontrol(node.body, node.body, node)) {
// replace labelled statement with its non-labelled body
node.start._permute = REPLACEMENTS.length;
CHANGED = true;
return node.body;
}
}
if (in_list) {
// drop switch branches
if (parent instanceof U.AST_Switch && parent.expression != node) {
node.start._permute++;
CHANGED = true;
return List.skip;
}
// replace or skip statement
if (node instanceof U.AST_Statement) {
node.start._permute++;
CHANGED = true;
return List.skip;
}
// remove this node unless its the sole element of a (transient) sequence
if (!(parent instanceof U.AST_Sequence) || parent.expressions.length > 1) {
node.start._permute++;
CHANGED = true;
return List.skip;
}
} else if (parent.rest === node) {
node.start._permute++;
CHANGED = true;
return null;
}
// replace this node
var newNode = U.is_statement(node) ? new U.AST_EmptyStatement({
start: {},
}) : U.parse(REPLACEMENTS[node.start._permute % REPLACEMENTS.length | 0], {
expression: true,
});
newNode.start._permute = ++node.start._permute;
CHANGED = true;
return newNode;
}, function(node, in_list) {
if (node instanceof U.AST_Definitions) {
// remove empty var statement
if (node.definitions.length == 0) return in_list ? List.skip : new U.AST_EmptyStatement({
start: {},
});
} else if (node instanceof U.AST_ObjectMethod) {
if (!/Function$/.test(node.value.TYPE)) return new U.AST_ObjectKeyVal({
key: node.key,
value: node.value,
start: {},
});
} else if (node instanceof U.AST_Sequence) {
// expand single-element sequence
if (node.expressions.length == 1) return node.expressions[0];
} else if (node instanceof U.AST_Try) {
// expand orphaned try block
if (!node.bcatch && !node.bfinally) return new U.AST_BlockStatement({
body: node.body,
start: {},
});
}
});
var diff_error_message;
for (var pass = 1; pass <= 3; ++pass) {
var testcase_ast = U.parse(testcase);
if (diff_error_message === testcase) {
// only difference detected is in error message, so expose that and try again
testcase_ast.transform(new U.TreeTransformer(function(node, descend) {
if (node.TYPE == "Call" && node.expression.print_to_string() == "console.log") {
return to_sequence(node.args);
}
if (node instanceof U.AST_Catch && node.argname instanceof U.AST_SymbolCatch) {
descend(node, this);
node.body.unshift(new U.AST_SimpleStatement({
body: wrap_with_console_log(new U.AST_SymbolRef(node.argname)),
start: {},
}));
return node;
}
}));
var code = testcase_ast.print_to_string(print_options);
var diff = test_for_diff(code, minify_options, result_cache, max_timeout);
if (diff && !diff.timed_out && !diff.error) {
testcase = code;
differs = diff;
} else {
testcase_ast = U.parse(testcase);
}
}
diff_error_message = null;
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;
}));
var before_iterations = testcase;
for (var c = 0; c < max_iterations; ++c) {
if (verbose && pass == 1 && c % 25 == 0) {
log("// 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(print_options);
} catch (ex) {
// AST is not well formed.
// no harm done - just log the error, ignore latest change and continue iterating.
log("*** Error generating code from AST.");
log(ex.stack);
log("*** Discarding permutation and continuing.");
continue;
}
var diff = test_for_diff(code, minify_options, result_cache, max_timeout);
if (diff) {
if (diff.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.
} else if (diff.error) {
// something went wrong during minify() - could be malformed AST or genuine bug.
// no harm done - just log code & error, ignore latest change and continue iterating.
log("*** Error during minification.");
log(code);
log(diff.error.stack);
log("*** Discarding permutation and continuing.");
} else if (sandbox.is_error(diff.unminified_result)
&& sandbox.is_error(diff.minified_result)
&& diff.unminified_result.name == diff.minified_result.name) {
// ignore difference in error messages caused by minification
diff_error_message = testcase;
} else {
// latest permutation is valid, so use it as the basis of new changes
testcase_ast = code_ast;
testcase = code;
differs = diff;
}
}
}
if (before_iterations === testcase) break;
if (verbose) {
log("// reduce test pass " + pass + ": " + testcase.length + " bytes");
}
}
var beautified = U.minify(testcase, {
compress: false,
mangle: false,
output: function() {
var options = JSON.parse(JSON.stringify(print_options));
options.beautify = true;
options.braces = true;
options.comments = true;
return options;
}(),
});
testcase = {
code: testcase,
};
if (!beautified.error) {
diff = test_for_diff(beautified.code, minify_options, result_cache, max_timeout);
if (diff && !diff.timed_out && !diff.error) {
testcase = beautified;
testcase.code = "// (beautified)\n" + testcase.code;
differs = diff;
}
}
var lines = [ "" ];
if (isNaN(max_timeout)) {
lines.push("// minify error: " + to_comment(differs.minified_result.stack));
} else {
var unminified_result = differs.unminified_result;
var minified_result = differs.minified_result;
if (trim_trailing_whitespace(unminified_result) == trim_trailing_whitespace(minified_result)) {
lines.push(
"// (stringified)",
"// output: " + JSON.stringify(unminified_result),
"// minify: " + JSON.stringify(minified_result)
);
} else {
lines.push(
"// output: " + to_comment(unminified_result),
"// minify: " + to_comment(minified_result)
);
}
}
lines.push("// options: " + to_comment(minify_options_json));
testcase.code += lines.join("\n");
testcase.warnings = warnings;
return testcase;
}
};
function to_comment(value) {
return ("" + value).replace(/\n/g, "\n// ");
}
function trim_trailing_whitespace(value) {
return ("" + value).replace(/\s+$/, "");
}
function has_exit(fn) {
var found = false;
var tw = new U.TreeWalker(function(node) {
if (found) return found;
if (node instanceof U.AST_Exit) {
return found = true;
}
if (node instanceof U.AST_Scope && node !== fn) {
return true; // don't descend into nested functions
}
});
fn.walk(tw);
return found;
}
function has_loopcontrol(body, loop, label) {
var found = false;
var tw = new U.TreeWalker(function(node) {
if (found) return true;
if (node instanceof U.AST_LoopControl && this.loopcontrol_target(node) === loop) {
return found = true;
}
});
if (label instanceof U.AST_LabeledStatement) tw.push(label);
tw.push(loop);
body.walk(tw);
return found;
}
function can_hoist(body) {
var found = false;
body.walk(new U.TreeWalker(function(node) {
if (found) return true;
if (node instanceof U.AST_NewTarget) return found = true;
if (node instanceof U.AST_Scope) {
if (node === body) return;
return true;
}
if (node instanceof U.AST_Super) return found = true;
}));
return !found;
}
function is_timed_out(result) {
return sandbox.is_error(result) && /timed out/.test(result.message);
}
function merge_sequence(array, node) {
if (node instanceof U.AST_Sequence) {
array.push.apply(array, node.expressions);
} else {
array.push(node);
}
return array;
}
function to_sequence(expressions) {
if (expressions.length == 0) return new U.AST_Number({value: 0, start: {}});
if (expressions.length == 1) return expressions[0];
return new U.AST_Sequence({
expressions: expressions.reduce(merge_sequence, []),
start: {},
});
}
function to_statement(node) {
return U.is_statement(node) ? node : new U.AST_SimpleStatement({
body: node,
start: {},
});
}
function to_statement_init(node) {
return node instanceof U.AST_Const || node instanceof U.AST_Let ? new U.AST_BlockStatement({
body: [ node ],
start: {},
}) : to_statement(node);
}
function wrap_with_console_log(node) {
// wrap with console.log()
return new U.AST_Call({
expression: new U.AST_Dot({
expression: new U.AST_SymbolRef({
name: "console",
start: {},
}),
property: "log",
start: {},
}),
args: [ node ],
start: {},
});
}
function run_code(code, toplevel, result_cache, timeout) {
var key = crypto.createHash("sha1").update(code).digest("base64");
var value = result_cache[key];
if (!value) {
var start = Date.now();
result_cache[key] = value = {
result: sandbox.run_code(sandbox.patch_module_statements(code), toplevel, timeout),
elapsed: Date.now() - start,
};
}
return value;
}
function compare_run_code(code, minify_options, result_cache, max_timeout) {
var minified = U.minify(code, minify_options);
if (minified.error) return minified;
var toplevel = sandbox.has_toplevel(minify_options);
var unminified = run_code(code, toplevel, result_cache, max_timeout);
var timeout = Math.min(100 * unminified.elapsed, max_timeout);
var minified_result = run_code(minified.code, toplevel, result_cache, timeout).result;
if (sandbox.same_stdout(unminified.result, minified_result)) {
return is_timed_out(unminified.result) && is_timed_out(minified_result) && {
timed_out: true,
};
}
return {
unminified_result: unminified.result,
minified_result: minified_result,
elapsed: unminified.elapsed,
};
}
function test_minify(code, minify_options) {
var minified = U.minify(code, minify_options);
return minified.error && {
minified_result: minified.error,
};
}
