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assert: make assertion_error use Myers diff algorithm
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Fixes: #51733

Co-Authored-By: Pietro Marchini <[email protected]>
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@puskin94 @pmarchini
puskin94 and pmarchini committed Sep 15, 2024
1 parent 9404d3a commit 27c553c
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Showing 9 changed files with 719 additions and 438 deletions.
310 changes: 57 additions & 253 deletions lib/internal/assert/assertion_error.js
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Original file line number Diff line number Diff line change
@@ -1,31 +1,27 @@
'use strict';

const {
ArrayIsArray,
ArrayPrototypeJoin,
ArrayPrototypePop,
Error,
ErrorCaptureStackTrace,
MathMax,
Map,
Object,
ObjectAssign,
ObjectDefineProperty,
ObjectGetPrototypeOf,
ObjectKeys,
String,
StringPrototypeEndsWith,
StringPrototypeRepeat,
StringPrototypeSlice,
StringPrototypeSplit,
} = primordials;

const { inspect } = require('internal/util/inspect');
const {
removeColors,
} = require('internal/util');
const colors = require('internal/util/colors');
const {
validateObject,
} = require('internal/validators');
const { validateObject } = require('internal/validators');
const { isErrorStackTraceLimitWritable } = require('internal/errors');

const { myersDiff, printMyersDiff } = require('internal/assert/myers_diff');

const kReadableOperator = {
deepStrictEqual: 'Expected values to be strictly deep-equal:',
Expand All @@ -41,269 +37,77 @@ const kReadableOperator = {
notDeepEqualUnequal: 'Expected values not to be loosely deep-equal:',
};

// Comparing short primitives should just show === / !== instead of using the
// diff.
const kMaxShortLength = 12;

function copyError(source) {
const target = ObjectAssign({ __proto__: ObjectGetPrototypeOf(source) }, source);
ObjectDefineProperty(target, 'message', { __proto__: null, value: source.message });
const target = ObjectAssign(
{ __proto__: ObjectGetPrototypeOf(source) },
source,
);
ObjectDefineProperty(target, 'message', {
__proto__: null,
value: source.message,
});
return target;
}

function inspectValue(val) {
// The util.inspect default values could be changed. This makes sure the
// error messages contain the necessary information nevertheless.
return inspect(
val,
{
compact: false,
customInspect: false,
depth: 1000,
maxArrayLength: Infinity,
// Assert compares only enumerable properties (with a few exceptions).
showHidden: false,
// Assert does not detect proxies currently.
showProxy: false,
sorted: true,
// Inspect getters as we also check them when comparing entries.
getters: true,
},
);
return inspect(val, {
compact: false,
customInspect: false,
depth: 1000,
maxArrayLength: Infinity,
// Assert compares only enumerable properties (with a few exceptions).
showHidden: false,
// Assert does not detect proxies currently.
showProxy: false,
sorted: true,
// Inspect getters as we also check them when comparing entries.
getters: true,
});
}

function createErrDiff(actual, expected, operator) {
let other = '';
let res = '';
let end = '';
let skipped = false;
const actualInspected = inspectValue(actual);
const actualLines = StringPrototypeSplit(actualInspected, '\n');
const expectedLines = StringPrototypeSplit(inspectValue(expected), '\n');
function showSimpleDiff(test) {
const isPrimitive = test !== Object(test);
const isEmptyArray = ArrayIsArray(test) && test.length === 0;
const isSimpleObject = !isPrimitive && !(test instanceof Map) && ObjectKeys(test).length === 0;

let i = 0;
let indicator = '';
return isPrimitive || isEmptyArray || isSimpleObject;
}

function checkOperator(actual, expected, operator) {
// In case both values are objects or functions explicitly mark them as not
// reference equal for the `strictEqual` operator.
if (operator === 'strictEqual' &&
((typeof actual === 'object' && actual !== null &&
typeof expected === 'object' && expected !== null) ||
(typeof actual === 'function' && typeof expected === 'function'))) {
if (
operator === 'strictEqual' &&
((typeof actual === 'object' &&
actual !== null &&
typeof expected === 'object' &&
expected !== null) ||
(typeof actual === 'function' && typeof expected === 'function'))
) {
operator = 'strictEqualObject';
}

// If "actual" and "expected" fit on a single line and they are not strictly
// equal, check further special handling.
if (actualLines.length === 1 && expectedLines.length === 1 &&
actualLines[0] !== expectedLines[0]) {
// Check for the visible length using the `removeColors()` function, if
// appropriate.
const c = inspect.defaultOptions.colors;
const actualRaw = c ? removeColors(actualLines[0]) : actualLines[0];
const expectedRaw = c ? removeColors(expectedLines[0]) : expectedLines[0];
const inputLength = actualRaw.length + expectedRaw.length;
// If the character length of "actual" and "expected" together is less than
// kMaxShortLength and if neither is an object and at least one of them is
// not `zero`, use the strict equal comparison to visualize the output.
if (inputLength <= kMaxShortLength) {
if ((typeof actual !== 'object' || actual === null) &&
(typeof expected !== 'object' || expected === null) &&
(actual !== 0 || expected !== 0)) { // -0 === +0
return `${kReadableOperator[operator]}\n\n` +
`${actualLines[0]} !== ${expectedLines[0]}\n`;
}
} else if (operator !== 'strictEqualObject') {
// If the stderr is a tty and the input length is lower than the current
// columns per line, add a mismatch indicator below the output. If it is
// not a tty, use a default value of 80 characters.
const maxLength = process.stderr.isTTY ? process.stderr.columns : 80;
if (inputLength < maxLength) {
while (actualRaw[i] === expectedRaw[i]) {
i++;
}
// Ignore the first characters.
if (i > 2) {
// Add position indicator for the first mismatch in case it is a
// single line and the input length is less than the column length.
indicator = `\n ${StringPrototypeRepeat(' ', i)}^`;
i = 0;
}
}
}
}

// Remove all ending lines that match (this optimizes the output for
// readability by reducing the number of total changed lines).
let a = actualLines[actualLines.length - 1];
let b = expectedLines[expectedLines.length - 1];
while (a === b) {
if (i++ < 3) {
end = `\n ${a}${end}`;
} else {
other = a;
}
ArrayPrototypePop(actualLines);
ArrayPrototypePop(expectedLines);
if (actualLines.length === 0 || expectedLines.length === 0)
break;
a = actualLines[actualLines.length - 1];
b = expectedLines[expectedLines.length - 1];
}

const maxLines = MathMax(actualLines.length, expectedLines.length);
// Strict equal with identical objects that are not identical by reference.
// E.g., assert.deepStrictEqual({ a: Symbol() }, { a: Symbol() })
if (maxLines === 0) {
// We have to get the result again. The lines were all removed before.
const actualLines = StringPrototypeSplit(actualInspected, '\n');

// Only remove lines in case it makes sense to collapse those.
// TODO: Accept env to always show the full error.
if (actualLines.length > 50) {
actualLines[46] = `${colors.blue}...${colors.white}`;
while (actualLines.length > 47) {
ArrayPrototypePop(actualLines);
}
}

return `${kReadableOperator.notIdentical}\n\n` +
`${ArrayPrototypeJoin(actualLines, '\n')}\n`;
}

// There were at least five identical lines at the end. Mark a couple of
// skipped.
if (i >= 5) {
end = `\n${colors.blue}...${colors.white}${end}`;
skipped = true;
}
if (other !== '') {
end = `\n ${other}${end}`;
other = '';
}
return operator;
}

let printedLines = 0;
let identical = 0;
const msg = kReadableOperator[operator] +
`\n${colors.green}+ actual${colors.white} ${colors.red}- expected${colors.white}`;
const skippedMsg = ` ${colors.blue}...${colors.white} Lines skipped`;
function createErrDiff(actual, expected, operator) {
operator = checkOperator(actual, expected, operator);
const nopSkippedMessage = `\n${colors.blue}...${colors.white} Skipped unchanged lines`;
const insertedSkippedMessage = `\n${colors.green}...${colors.white} Skipped added lines`;
const deletedSkippedMessage = `\n${colors.red}...${colors.white} Skipped removed lines`;

let lines = actualLines;
let plusMinus = `${colors.green}+${colors.white}`;
let maxLength = expectedLines.length;
if (actualLines.length < maxLines) {
lines = expectedLines;
plusMinus = `${colors.red}-${colors.white}`;
maxLength = actualLines.length;
}
const simpleDiff = showSimpleDiff(actual) && showSimpleDiff(expected);
const isStringComparison = typeof actual === 'string' && typeof expected === 'string';
const header = simpleDiff ? '' : `${colors.green}+ actual${colors.white} ${colors.red}- expected${colors.white}`;
const headerMessage = `${kReadableOperator[operator]}\n${header}`;

for (i = 0; i < maxLines; i++) {
if (maxLength < i + 1) {
// If more than two former lines are identical, print them. Collapse them
// in case more than five lines were identical.
if (identical > 2) {
if (identical > 3) {
if (identical > 4) {
if (identical === 5) {
res += `\n ${lines[i - 3]}`;
printedLines++;
} else {
res += `\n${colors.blue}...${colors.white}`;
skipped = true;
}
}
res += `\n ${lines[i - 2]}`;
printedLines++;
}
res += `\n ${lines[i - 1]}`;
printedLines++;
}
// No identical lines before.
identical = 0;
// Add the expected line to the cache.
if (lines === actualLines) {
res += `\n${plusMinus} ${lines[i]}`;
} else {
other += `\n${plusMinus} ${lines[i]}`;
}
printedLines++;
// Only extra actual lines exist
// Lines diverge
} else {
const expectedLine = expectedLines[i];
let actualLine = actualLines[i];
// If the lines diverge, specifically check for lines that only diverge by
// a trailing comma. In that case it is actually identical and we should
// mark it as such.
let divergingLines =
actualLine !== expectedLine &&
(!StringPrototypeEndsWith(actualLine, ',') ||
StringPrototypeSlice(actualLine, 0, -1) !== expectedLine);
// If the expected line has a trailing comma but is otherwise identical,
// add a comma at the end of the actual line. Otherwise the output could
// look weird as in:
//
// [
// 1 // No comma at the end!
// + 2
// ]
//
if (divergingLines &&
StringPrototypeEndsWith(expectedLine, ',') &&
StringPrototypeSlice(expectedLine, 0, -1) === actualLine) {
divergingLines = false;
actualLine += ',';
}
if (divergingLines) {
// If more than two former lines are identical, print them. Collapse
// them in case more than five lines were identical.
if (identical > 2) {
if (identical > 3) {
if (identical > 4) {
if (identical === 5) {
res += `\n ${actualLines[i - 3]}`;
printedLines++;
} else {
res += `\n${colors.blue}...${colors.white}`;
skipped = true;
}
}
res += `\n ${actualLines[i - 2]}`;
printedLines++;
}
res += `\n ${actualLines[i - 1]}`;
printedLines++;
}
// No identical lines before.
identical = 0;
// Add the actual line to the result and cache the expected diverging
// line so consecutive diverging lines show up as +++--- and not +-+-+-.
res += `\n${colors.green}+${colors.white} ${actualLine}`;
other += `\n${colors.red}-${colors.white} ${expectedLine}`;
printedLines += 2;
// Lines are identical
} else {
// Add all cached information to the result before adding other things
// and reset the cache.
res += other;
other = '';
identical++;
// The very first identical line since the last diverging line is be
// added to the result.
if (identical <= 2) {
res += `\n ${actualLine}`;
printedLines++;
}
}
}
// Inspected object to big (Show ~50 rows max)
if (printedLines > 50 && i < maxLines - 2) {
return `${msg}${skippedMsg}\n${res}\n${colors.blue}...${colors.white}${other}\n` +
`${colors.blue}...${colors.white}`;
}
}
const diff = myersDiff(actual, expected);
const { message, skipped } = printMyersDiff(diff, simpleDiff, isStringComparison);
const skippedMessahe = skipped ? `${nopSkippedMessage}${insertedSkippedMessage}${deletedSkippedMessage}` : '';

return `${msg}${skipped ? skippedMsg : ''}\n${res}${other}${end}${indicator}`;
return `${headerMessage}${skippedMessahe}\n${message}\n`;
}

function addEllipsis(string) {
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