hardhat-preprocessor
This plugin allows to pre-process contract source code before compilation
Hardhat preprocessor plugin.
What
This plugin allow you to specify a function that is executed on every line of all contracts so that you can pre-process the code.
A typical example (included) is to remove console.log for production ready contracts.
Note that this plugin, by default, does not touch the filesystem. It happens in memory and transform contract on-demand.
This is done by simply importing the plugin in the hardhat.config.js
It also include a task that can be invoked to render the transformation on disk instead.
Installation
npm install hardhat-preprocessor
And add the following statement to your hardhat.config.js
:
import 'hardhat-preprocessor';
Required plugins
Nothing required
Tasks
hardhat-preprocessor
also add a new task: preprocess
hardhat preprocess [--dest <destination folder>]
This task will write the modification to disk. By default it overwrite the sources. if the dest
option is set, it will write in that folder instead (and keep sources intact).
Environment extensions
No extra fields added to the envirobment.
Configuration
This plugin extends the Hardhat Config with one new field: preprocess
This field is an object with a field : eachLine
that itself is a function that accept the HRE as argument and must return either an object with a transform
field or a promise to such object.
The transform
function expect a string as argument (a line of a contract) and must return a string.
The object containing the transform
function can also have a settings
field that is used for caching. If no settings field is set, no caching will take place and contracts will be recompiled. If the settings field is set, then the contract will be recompiled only if the settings changed.
Note that instead of returning (or resolving a function), it is possible to return undefined to skip the preprocessing entirely. This will recompile contract if the previous invocation had returned something.
Basic example that add a comment on each line:
import 'hardhat-preprocessor';
export default {
preprocess: {
eachLine: (hre) => ({
transform: (line) => line + '// comment at the end of each line',
settings: {comment: true} // ensure the cache is working, in that example it can be anything as there is no option, the preprocessing happen all the time
})
},
};
The plugin comes also with a preprocess function to remove console.log
(achieving the same thing as this plugin but without changing the files on disk)
You can use it as follow :
import {removeConsoleLog} from 'hardhat-preprocessor';
export default {
preprocess: {
eachLine: removeConsoleLog((hre) => hre.network.name !== 'hardhat' && hre.network.name !== 'localhost'),
},
};
In this example the preprocessing do not happen when used against hardhat (testing) or localhost
Usage
There are no additional steps you need to take for this plugin to work.