#Stats

The stats object that is passed as a second argument of the rspack() callback, is a good source of information about the code compilation process. It includes:

• Errors and Warnings (if any)
• Timings
• Module and Chunk information

The Stats object provides two important methods:

• toJson(): Output information in the form of a Stats JSON object, which is often used in analysis tools.
• toString(): Output information in the form of a string, which is often used in the CLI tools.

Rspack also provides StatsFactory and StatsPrinter to fine-grained control the output object or string.

Compilation ===============> Stats JSON =================> Stats Output
           ╰─ StatsFactory ─╯           ╰─ StatsPrinter ─╯
╰─────────── stats.toJson() ───────────╯
╰───────────────────────── stats.toString() ──────────────────────────╯

Create a stats object related to a compilation through compilation.getStats() or new Stats(compilation).

#Stats methods

#hasErrors

Can be used to check if there were errors while compiling.

hasErrors(): boolean;

#hasWarnings

Can be used to check if there were warnings while compiling.

hasWarnings(): boolean;

#toJson

Return the compilation information in the form of a Stats JSON object. The Stats configuration can be a string (preset value) or an object for granular control:

stats.toJson('minimal');

stats.toJson({
  assets: false,
  hash: true,
});

#toString

Return the compilation information in the form of a formatted string (similar to the output of CLI).

toJson(opts?: StatsValue): string;

Options are the same as stats.toJson(options) with one addition:

stats.toString({
  // Add console colors
  colors: true,
});

Here's an example of stats.toString() usage:

import { rspack } from '@rspack/core';

rspack(
  {
    // ...
  },
  (err, stats) => {
    if (err) {
      console.error(err);
      return;
    }

    console.log(
      stats.toString({
        chunks: false, // Makes the build much quieter
        colors: true, // Shows colors in the console
      }),
    );
  },
);

#Stats properties

#compilation

Type: Compilation

Get the related compilation object.

#hash

Type: string

Get the hash of this compilation, same as Compilation.hash.

#MultiStats

When using MultiCompiler to execute multiple compilation tasks, their compilation stats will be packaged as a MultiStats object, which provides similar methods and properties as Stats.

#hash

Type: string

Get the unique hash after merging the hashes of all compilations.

#hasErrors

Used to check if there are errors during the compilation period, and only if there are no errors in all compilations will it return false.

hasErrors(): boolean;

#hasWarnings

Used to check if there are warnings during the compilation period, and only if there are no warnings in all compilations will it return false.

hasWarnings(): boolean;

#toJson

According to the stats configuration, generate all the stats json objects, wrap them in the children field, and also summarize the errors and warnings.

toJson(options?: StatsValue): {
  hash: string;
  errorsCount: number;
  warningsCount: number;
  errors: StatsError[];
  warnings: StatsError[];
  children: StatsCompilation[];
};

#toString

Concatenate the stats output strings of all compilations according to the stats configuration.

toString(options?: StatsValue): string;

#Stats factory

Used to generate the stats json object from the Compilation, and provides hooks for fine-grained control during the generation process.

It can be got through compilation.hooks.statsFactory. Or create a new one by new StatsFactory().

#Hooks

See StatsFactory hooks for more details.

#create

The core method of StatsFactory, according to the type to specify the current data structure, find and run the corresponding generator to generate the stats json item.

stats = statsFactory.create('compilation', compilation, {});

The StatsFactory object only handles the calling of hooks, and the processing code of the corresponding type can be found in DefaultStatsFactoryPlugin.

#Stats printer

Used to generate the output string from the stats json object, and provides hooks for fine-grained control during the generation process.

It can be got through compilation.hooks.statsPrinter. Or create a new one by new StatsPrinter().

#Hooks

See StatsPrinter hooks for more details.

#print

The core method of StatsPrinter, according to the type to specify the current data structure, find and run the corresponding generator to generate the output string of the stats item.

stats = statsPrinter.print('compilation', stats, {});

The StatsPrinter object only handles the calling of hooks, and the processing code of the corresponding type can be found in DefaultStatsPrinterPlugin.