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Rspack will select appropriate optimization configuration based on the mode
. You can also customize the configuration via optimization
.
'natural' | 'named' | 'deterministic'
option | description |
---|---|
natural |
Use numeric ids in order of usage. |
named |
Use meaningful, easy-to-debug content as id. This option is enabled by default in development mode. |
deterministic |
Use the hashed module identifier as the id to benefit from long-term caching. This option is enabled by default in production mode. |
'named' | 'deterministic'
option | description |
---|---|
'named' |
Readable ids for better debugging. This option is enabled by default in development mode |
'deterministic' |
Short numeric ids which will not be changing between compilation. Good for long term caching. This option is enabled by default in production mode. |
boolean
true
, development mode isfalse
Whether to minimize the bundle.
boolean
true
Whether to merge chunks which contain the same modules. Setting optimization.mergeDuplicateChunks to false will disable this optimization.
Array<Plugin>
[new SwcJsMinimizerRspackPlugin(), new LightningCssMinimizerRspackPlugin()]
Customize the minimizer. By default, rspack.SwcJsMinimizerRspackPlugin
and rspack.LightningCssMinimizerRspackPlugin
are used.
When optimization.minimizer
is specified, the default minimizers will be disabled.
Use the built-in minimizer with custom options:
boolean
true
Remove empty chunks generated in the compilation.
boolean | string | ((entrypoint: { name: string }) => string)
false
Used to control how the runtime chunk is generated.
Setting it to true
or 'multiple'
will add an additional chunk containing only the runtime for each entry point.
Setting it to 'single'
will extract the runtime code of all entry points into a single separate chunk.
boolean | 'flag'
true
, development mode isfalse
Adds an additional hash compilation pass after the assets have been processed to get the correct asset content hashes. This feature will enable by default in production mode.
If realContentHash is set to false, internal data is used to calculate the hash and it can change when assets are identical in some cases.
false | object
Rspack supports splitting chunks with the optimization.splitChunks
configuration item.
It is enabled by default for dynamically imported modules.
To turn it off, set it to false
.
See available options for configuring this behavior in the SplitChunksPlugin page.
boolean | 'flag'
true
, development mode is'flag'
Tells Rspack to recognise the sideEffects flag in package.json or rules to skip over modules which are flagged to contain no side effects when exports are not used.
Please note that sideEffects
should be in the npm module's package.json
file and doesn't mean that you need to set sideEffects
to false
in your own project's package.json
which requires that npm module.
optimization.sideEffects
depends on optimization.providedExports
to be enabled.
This dependency has a build time cost, but eliminating modules has positive impact on performance because of less code generation.
Effect of this optimization depends on your codebase, try it for possible performance wins.
If you only want Rspack use the manual sideEffects
flag via (package.json
and module.rule.sideEffects
) and don't analyse source code:
The 'flag'
value is used by default in non-production builds.
When optimization.sideEffects
is true , Rspack will also flag modules as side effect free when they contain only side effect free statements.
boolean
true
After enabling, Rspack will analyze which exports the module provides, including re-exported modules. A warning or error will be issued when importing members that reference non-existent exports. By default, optimization.providedExports
is enabled. This analysis will increase build time. You may consider disabling this configuration in development mode. Disabling it may lead to errors related to runtime circular dependencies as mentioned in the SideEffects section.
boolean | 'global'
true
, development mode isfalse
Tells Rspack to determine used exports for each module. This depends on optimization.providedExports
.
Information collected by optimization.usedExports
is used by other optimizations or code generation i.e.
Exports are not generated for unused exports, export names are mangled to single char identifiers when all usages are compatible. Dead code elimination in minimizers will benefit from this and can remove unused exports.
To opt-out from used exports analysis per runtime:
boolean | 'deterministic' | 'size'
deterministic
, development mode isfalse
optimization.mangleExports
allows to control export mangling.
The following values are supported:
option | description |
---|---|
'named' | Use meaningful, easy-to-debug content as id. This option is enabled by default in development mode |
'deterministic' | Use the hashed module identifier as the id to benefit from long-term caching. This option is enabled by default in production mode |
true | Same as 'deterministic' |
false | Keep original name. Good for readability and debugging. |
boolean
true
, development mode isfalse
optimization.innerGraph
tells Rspack whether to perform a more detailed analysis of variable assignments. This helps Rspack to identify unused module exports, thereby reducing the size of the bundled output.
For example:
Here we assign the value
to value2
. Both value2
and value
are accessed within the functions f2
and f1
respectively, but the functions are not called, hence value2
and value
are not actually used, thus the import of value
can be removed.
boolean
true
, development mode isfalse
Tells Rspack to find segments of the module graph which can be safely concatenated into a single module. Depends on optimization.providedExports and optimization.usedExports. By default optimization.concatenateModules
is enabled in production
mode and disabled elsewise.
boolean | string
false
Tells Rspack to set process.env.NODE_ENV
to a given string value. optimization.nodeEnv
uses DefinePlugin unless set to false.
optimization.nodeEnv
defaults to mode if set, else falls back to 'production'
.
Possible values:
process.env.NODE_ENV
to.process.env.NODE_ENV
.When mode is set to 'none'
, optimization.nodeEnv
defaults to false
.
boolean
false
, development mode istrue
Use the optimization.emitOnErrors
to emit assets whenever there are errors while compiling. This ensures that erroring assets are emitted. Critical errors are emitted into the generated code and will cause errors at runtime.