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util: add util.inspect compact option
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The current default formatting is not ideal and this improves
the situation by formatting the output more intuitiv.

1) All object keys are now indented by 2 characters instead of
   sometimes 2 and sometimes 3 characters.
2) Each object key will now use an individual line instead of
   sharing a line potentially with multiple object keys.
3) Long strings will now be split into multiple lines in case
   they exceed the "lineBreak" option length (including the
   current indentation).
4) Opening braces are now directly behind a object property
   instead of using a new line.
5) Switch inspect "base" order. In case the compact option is set
   to `false`, inspect will now print
     "[Function: foo] {\n  property: 'data'\n}"
   instead of
     "{ [Function: foo]\n  property: 'data'\n}".

Backport-PR-URL: #19230
PR-URL: #17576
Reviewed-By: Anna Henningsen <[email protected]>
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@BridgeAR @MylesBorins
BridgeAR authored and MylesBorins committed Mar 20, 2018
1 parent ce3a5af commit c18ac52
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67 changes: 67 additions & 0 deletions doc/api/util.md
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Original file line number Diff line number Diff line change
Expand Up @@ -316,6 +316,9 @@ stream.write('With ES6');
<!-- YAML
added: v0.3.0
changes:
- version: REPLACEME
pr-url: https://github.com/nodejs/node/pull/REPLACEME
description: The `compact` option is supported now.
- version: v6.6.0
pr-url: https://github.com/nodejs/node/pull/8174
description: Custom inspection functions can now return `this`.
Expand Down Expand Up @@ -353,6 +356,13 @@ changes:
* `breakLength` {number} The length at which an object's keys are split
across multiple lines. Set to `Infinity` to format an object as a single
line. Defaults to 60 for legacy compatibility.
* `compact` {boolean} Setting this to `false` changes the default indentation
to use a line break for each object key instead of lining up multiple
properties in one line. It will also break text that is above the
`breakLength` size into smaller and better readable chunks and indents
objects the same as arrays. Note that no text will be reduced below 16
characters, no matter the `breakLength` size. For more information, see the
example below. Defaults to `true`.

The `util.inspect()` method returns a string representation of `object` that is
primarily useful for debugging. Additional `options` may be passed that alter
Expand All @@ -370,6 +380,63 @@ Values may supply their own custom `inspect(depth, opts)` functions, when
called these receive the current `depth` in the recursive inspection, as well as
the options object passed to `util.inspect()`.

The following example highlights the difference with the `compact` option:

```js
const util = require('util');

const o = {
a: [1, 2, [[
'Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do ' +
'eiusmod tempor incididunt ut labore et dolore magna aliqua.',
'test',
'foo']], 4],
b: new Map([['za', 1], ['zb', 'test']])
};
console.log(util.inspect(o, { compact: true, depth: 5, breakLength: 80 }));

// This will print

// { a:
// [ 1,
// 2,
// [ [ 'Lorem ipsum dolor sit amet, consectetur [...]', // A long line
// 'test',
// 'foo' ] ],
// 4 ],
// b: Map { 'za' => 1, 'zb' => 'test' } }

// Setting `compact` to false changes the output to be more reader friendly.
console.log(util.inspect(o, { compact: false, depth: 5, breakLength: 80 }));

// {
// a: [
// 1,
// 2,
// [
// [
// 'Lorem ipsum dolor sit amet, consectetur ' +
// 'adipiscing elit, sed do eiusmod tempor ' +
// 'incididunt ut labore et dolore magna ' +
// 'aliqua.,
// 'test',
// 'foo'
// ]
// ],
// 4
// ],
// b: Map {
// 'za' => 1,
// 'zb' => 'test'
// }
// }

// Setting `breakLength` to e.g. 150 will print the "Lorem ipsum" text in a
// single line.
// Reducing the `breakLength` will split the "Lorem ipsum" text in smaller
// chunks.
```

### Customizing `util.inspect` colors

<!-- type=misc -->
Expand Down
84 changes: 67 additions & 17 deletions lib/util.js
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Original file line number Diff line number Diff line change
Expand Up @@ -68,7 +68,8 @@ const inspectDefaultOptions = Object.seal({
customInspect: true,
showProxy: false,
maxArrayLength: 100,
breakLength: 60
breakLength: 60,
compact: true
});

const propertyIsEnumerable = Object.prototype.propertyIsEnumerable;
Expand All @@ -86,6 +87,10 @@ const strEscapeSequencesReplacer = /[\x00-\x1f\x27\x5c]/g;
const keyStrRegExp = /^[a-zA-Z_][a-zA-Z_0-9]*$/;
const numberRegExp = /^(0|[1-9][0-9]*)$/;

const readableRegExps = {};

const MIN_LINE_LENGTH = 16;

// Escaped special characters. Use empty strings to fill up unused entries.
const meta = [
'\\u0000', '\\u0001', '\\u0002', '\\u0003', '\\u0004',
Expand Down Expand Up @@ -276,7 +281,8 @@ function inspect(value, opts) {
showProxy: inspectDefaultOptions.showProxy,
maxArrayLength: inspectDefaultOptions.maxArrayLength,
breakLength: inspectDefaultOptions.breakLength,
indentationLvl: 0
indentationLvl: 0,
compact: inspectDefaultOptions.compact
};
// Legacy...
if (arguments.length > 2) {
Expand Down Expand Up @@ -374,7 +380,7 @@ function ensureDebugIsInitialized() {
function formatValue(ctx, value, recurseTimes, ln) {
// Primitive types cannot have properties
if (typeof value !== 'object' && typeof value !== 'function') {
return formatPrimitive(ctx.stylize, value);
return formatPrimitive(ctx.stylize, value, ctx);
}
if (value === null) {
return ctx.stylize('null', 'null');
Expand Down Expand Up @@ -481,10 +487,10 @@ function formatValue(ctx, value, recurseTimes, ln) {
} catch (e) { /* ignore */ }

if (typeof raw === 'string') {
const formatted = formatPrimitive(stylizeNoColor, raw);
const formatted = formatPrimitive(stylizeNoColor, raw, ctx);
if (keyLength === raw.length)
return ctx.stylize(`[String: ${formatted}]`, 'string');
base = ` [String: ${formatted}]`;
base = `[String: ${formatted}]`;
// For boxed Strings, we have to remove the 0-n indexed entries,
// since they just noisy up the output and are redundant
// Make boxed primitive Strings look like such
Expand All @@ -505,25 +511,25 @@ function formatValue(ctx, value, recurseTimes, ln) {
const name = `${constructor.name}${value.name ? `: ${value.name}` : ''}`;
if (keyLength === 0)
return ctx.stylize(`[${name}]`, 'special');
base = ` [${name}]`;
base = `[${name}]`;
} else if (isRegExp(value)) {
// Make RegExps say that they are RegExps
if (keyLength === 0 || recurseTimes < 0)
return ctx.stylize(regExpToString.call(value), 'regexp');
base = ` ${regExpToString.call(value)}`;
base = `${regExpToString.call(value)}`;
} else if (isDate(value)) {
if (keyLength === 0) {
if (Number.isNaN(value.getTime()))
return ctx.stylize(value.toString(), 'date');
return ctx.stylize(dateToISOString.call(value), 'date');
}
// Make dates with properties first say the date
base = ` ${dateToISOString.call(value)}`;
base = `${dateToISOString.call(value)}`;
} else if (isError(value)) {
// Make error with message first say the error
if (keyLength === 0)
return formatError(value);
base = ` ${formatError(value)}`;
base = `${formatError(value)}`;
} else if (isAnyArrayBuffer(value)) {
// Fast path for ArrayBuffer and SharedArrayBuffer.
// Can't do the same for DataView because it has a non-primitive
Expand Down Expand Up @@ -553,13 +559,13 @@ function formatValue(ctx, value, recurseTimes, ln) {
const formatted = formatPrimitive(stylizeNoColor, raw);
if (keyLength === 0)
return ctx.stylize(`[Number: ${formatted}]`, 'number');
base = ` [Number: ${formatted}]`;
base = `[Number: ${formatted}]`;
} else if (typeof raw === 'boolean') {
// Make boxed primitive Booleans look like such
const formatted = formatPrimitive(stylizeNoColor, raw);
if (keyLength === 0)
return ctx.stylize(`[Boolean: ${formatted}]`, 'boolean');
base = ` [Boolean: ${formatted}]`;
base = `[Boolean: ${formatted}]`;
} else if (typeof raw === 'symbol') {
const formatted = formatPrimitive(stylizeNoColor, raw);
return ctx.stylize(`[Symbol: ${formatted}]`, 'symbol');
Expand Down Expand Up @@ -603,9 +609,42 @@ function formatNumber(fn, value) {
return fn(`${value}`, 'number');
}

function formatPrimitive(fn, value) {
if (typeof value === 'string')
function formatPrimitive(fn, value, ctx) {
if (typeof value === 'string') {
if (ctx.compact === false &&
value.length > MIN_LINE_LENGTH &&
ctx.indentationLvl + value.length > ctx.breakLength) {
// eslint-disable-next-line max-len
const minLineLength = Math.max(ctx.breakLength - ctx.indentationLvl, MIN_LINE_LENGTH);
// eslint-disable-next-line max-len
const averageLineLength = Math.ceil(value.length / Math.ceil(value.length / minLineLength));
const divisor = Math.max(averageLineLength, MIN_LINE_LENGTH);
var res = '';
if (readableRegExps[divisor] === undefined) {
// Build a new RegExp that naturally breaks text into multiple lines.
//
// Rules
// 1. Greedy match all text up the max line length that ends with a
// whitespace or the end of the string.
// 2. If none matches, non-greedy match any text up to a whitespace or
// the end of the string.
//
// eslint-disable-next-line max-len, no-unescaped-regexp-dot
readableRegExps[divisor] = new RegExp(`(.|\\n){1,${divisor}}(\\s|$)|(\\n|.)+?(\\s|$)`, 'gm');
}
const indent = ' '.repeat(ctx.indentationLvl);
const matches = value.match(readableRegExps[divisor]);
if (matches.length > 1) {
res += `${fn(strEscape(matches[0]), 'string')} +\n`;
for (var i = 1; i < matches.length - 1; i++) {
res += `${indent} ${fn(strEscape(matches[i]), 'string')} +\n`;
}
res += `${indent} ${fn(strEscape(matches[i]), 'string')}`;
return res;
}
}
return fn(strEscape(value), 'string');
}
if (typeof value === 'number')
return formatNumber(fn, value);
if (typeof value === 'boolean')
Expand Down Expand Up @@ -806,7 +845,7 @@ function formatProperty(ctx, value, recurseTimes, key, array) {
const desc = Object.getOwnPropertyDescriptor(value, key) ||
{ value: value[key], enumerable: true };
if (desc.value !== undefined) {
const diff = array === 0 ? 3 : 2;
const diff = array !== 0 || ctx.compact === false ? 2 : 3;
ctx.indentationLvl += diff;
str = formatValue(ctx, desc.value, recurseTimes, array === 0);
ctx.indentationLvl -= diff;
Expand Down Expand Up @@ -839,25 +878,36 @@ function formatProperty(ctx, value, recurseTimes, key, array) {

function reduceToSingleString(ctx, output, base, braces, addLn) {
const breakLength = ctx.breakLength;
var i = 0;
if (ctx.compact === false) {
const indentation = ' '.repeat(ctx.indentationLvl);
var res = `${base ? `${base} ` : ''}${braces[0]}\n${indentation} `;
for (; i < output.length - 1; i++) {
res += `${output[i]},\n${indentation} `;
}
res += `${output[i]}\n${indentation}${braces[1]}`;
return res;
}
if (output.length * 2 <= breakLength) {
var length = 0;
for (var i = 0; i < output.length && length <= breakLength; i++) {
for (; i < output.length && length <= breakLength; i++) {
if (ctx.colors) {
length += removeColors(output[i]).length + 1;
} else {
length += output[i].length + 1;
}
}
if (length <= breakLength)
return `${braces[0]}${base} ${join(output, ', ')} ${braces[1]}`;
return `${braces[0]}${base ? ` ${base}` : ''} ${join(output, ', ')} ` +
braces[1];
}
// If the opening "brace" is too large, like in the case of "Set {",
// we need to force the first item to be on the next line or the
// items will not line up correctly.
const indentation = ' '.repeat(ctx.indentationLvl);
const extraLn = addLn === true ? `\n${indentation}` : '';
const ln = base === '' && braces[0].length === 1 ?
' ' : `${base}\n${indentation} `;
' ' : `${base ? ` ${base}` : base}\n${indentation} `;
const str = join(output, `,\n${indentation} `);
return `${extraLn}${braces[0]}${ln}${str} ${braces[1]}`;
}
Expand Down
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