env-verifier
v1.5.0
Published
"Make sure you have all your env variables!"
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env-verifier
Verify that your environment variables exist, and build up your config object at the same time!
Package Purpose
Certain types of apps require the use of different variables depending on the environment that the app is run in.
The purpose of this package is to fail early whenever one of those values is missing from the environment object (ie: process.env
).
Using this package properly will prevent the sometimes cryptic errors that occur when environment variables are missing.
Because every missing environment variable that env-verifier
encountered is returned (or is displayed in a thrown error), this package can also help with the: run the app, app crashes because of missing environment variable, add environment variable, repeat
loop that sometimes occurs.
Getting Started
You probably have code that looks like this in your repo:
module.exports = {
database: {
name: process.env.DB_NAME
host: process.env.DB_HOST
password: process.env.DB_PASSWORD
},
baseUrl: process.env.BASE_URL
}
to get up and running quickly with a verified config file, you can replace the above with something like this:
const { strictVerify } = require('env-verifier')
//throws on one or more env misses
module.exports = strictVerify({
database: {
name: 'DB_NAME',
host: 'DB_HOST',
password: 'DB_PASSWORD'
},
baseUrl: 'BASE_URL'
})
This package exposes two verification functions - verify
and strictVerify
. Use verify
(as seen below) when you want to handle reporting missing values, and strictVerify
(as seen above) when you want, when any env
misses are encountered, a descriptive error containing all env
misses to be thrown.
Use example for verify
:
const { verify } = require('env-verifier')
const { config, missingValues } = verify({
database: {
name: 'DB_NAME'
host: 'DB_HOST'
password: 'DB_PASSWORD'
},
baseUrl: 'BASE_URL'
})
// do custom error logging, possibly throw your own errors
missingValues.forEach(
({ envKey, path }) => console.log(`missing env variable: ${envKey} from config at path: ${path}`)
)
module.exports = config
You can pass in your own env
object as a parameter as long as its an object that is non-nested and has key value pairs with undefined
or string
as their value type.
Usage Notes
- Function Parameters and Return Types
- Processing Missing Values
- Arbitrary Value Insertion
- Secret Insertion
- Error Generation and Reporting
- Variable Transformation
- Dynamic Typings
env-verifier
vsconvict
Function Parameters and Return Types
verify
export function insert<T>(value: T) => Insert<T> // see `Arbitrary Value Insertion` documentation
export function secret(envKey: string) => Secret // see `Secret Insertion` documentation
export function transform<T>(envKey: string, transformFn: (envValue: string) => T) => T // see `Variable Transformation` documentation
export function transformFP<T>(transformFn: (envValue: string) => T, envKey: string) => T
export function transformFP<T>(transformFn: (envValue: string) => T) => ((envKey: string) => T) // see `Variable Transformation` documentation
export type TransformTuple = [string, (envValue: string) => any]
// Type given as example only, the real type is a bit more complex
export type ConfigWithEnvKeys<T> = {
[P in keyof T]: string | TransformTuple | ReturnType<typeof insert> | ReturnType<typeof secret> | ConfigWithEnvKeys<T[P]>
}
// Type given as example only, the real type is a bit more complex
export type MappedConfig<T> = {
[P in keyof T]: string | null | ReturnType<typeof secret> | MappedConfig<T[P]> | any // ie: return type of `insert` or `TransformTuple` function
}
export type MissingValue = {
path: string
envKey: string
}
export function verify<T>(
config: ConfigWithEnvKeys<T>
env: { [key: string]: string | undefined } = process.env
): {
config: MappedConfig<T>,
missingValues: MissingValue[],
missingValueMessages: string[],
/**
* @deprecated Please use missingValueMessages
*/
errors: string[]
}
strictVerify
export function insert<T extends any>(value: T) => Insert<T> // see `Arbitrary Value Insertion` documentation
export function secret(envKey: string) => Secret // see `Secret Insertion` documentation
export type TransformTuple = [string, (envValue: string) => any]
// Type given as example only, the real type is a bit more complex
export type ConfigWithEnvKeys<T> = {
[P in keyof T]: string | TransformTuple | ReturnType<typeof insert> | ReturnType<typeof secret> | ConfigWithEnvKeys<T[P]>
}
// Type given as example only, the real type is a bit more complex
// Similar to MappedConfig<T>, but does not contain nulls (except for as returned by `TransformTuple` functions or `insert` calls)
export type VerifiedConfig<T> = {
[P in keyof T]: string | ReturnType<typeof secret> | VerifiedConfig<T[P]> | any // ie: return type of `insert` or `TransformTuple` function
}
export function strictVerify<T>(
config: ConfigWithEnvKeys<T>
env: { [key: string]: string | undefined } = process.env
): VerifiedConfig<T>
Processing Missing Values
An array of objects of type MissingValue
is returned from the verify
function.
type MissingValue = {
path: string
envKey: string
}
envKey
The key of the missing env
value.
path
The path in the config
argument to the missing env
variable.
Example:
import { verify } from 'env-verifier'
const config = {
db: {
password: 'DB_PASSWORD'
}
}
const env = {
DB_PASSWORD: undefined
}
const result = verify(config, env)
console.log(result.missingValues)
// results in:
// [{ path: 'db.password', envKey: 'DB_PASSWORD' }]
Arbitrary Value Insertion
You may have values that aren't present on your env
object, but that you would like to live in your config object, this can be achieved by using the insert()
function.
const { verify, insert } = require('env-verifier')
module.exports = verify({
appName: insert('my_app')
... // other env key names
}).config
//exports:
{
appName: 'my_app'
... // other env values
}
Secret Insertion
As of env-verifier version 1.2.0
, the obfuscation of env secrets is supported.
by wrapping the env key of the secret in the secret
function exported by env-verifier
, the secret will be retrieved and wrapped in a Secret
object (see function specification above).
Note: support for transforming or inserting secrets is not supported at this time.
To retrieve the secret, the reveal
function can be called.
What secret obfuscation will do:
- protect secrets from casual logging of the produced config object
JSON.stringify
of the config object will replace all secrets with the string'[secret]'
What secret obfuscation will not do:
- prevent the actually logging of the revealed secret
- mutate the actual string returned from the
env
object
const { verify, secret } = require('env-verifier')
const env = {
PASSWORD: 'superSecretPassword'
}
const { config } = verify({
password: secret('PASSWORD')
... // other env key names
}, env)
module.exports = config
//exports:
{
password: {
reveal(): string
}
... // other env values
}
config.password.reveal()
// returns:
'superSecretPassword'
console.log(config)
// prints:
// {
// if you're using nodejs:
// password: [secret]
// if you're using other JS environments:
// password: Secret { reveal: [Function] }
// ... other env values
// }
JSON.stringify(config)
// returns
// {
// "password": "[secret]"
// ... other env values
// }
Error Generation and Reporting
Error reports are generated when an env
variable is missing. An env
variable is considered missing under the following circumstances:
undefined
is returned from theenv
object.- an empty string,
''
, is returned from theenv
object. (useful for development with Docker)
verify
will always return an array of MissingValue
s, which will be empty if there are no env
misses.
strictVerify
will evaluate the entire config
object before throwing any errors in order to report all missing env
variables
Variable Transformation
Since env-verifier
only takes environment key-value pair objects that have strings
as the values, its sometimes necessary to transform those strings into something else (IE: transform the string "true"
to a boolean true
)
This can be done in two ways:
- By passing in an array (called a
TransformTuple
in this context) containing theenv
variable name, and the function that you would like to use to transform theenv
variable value - By calling the
transform
function which takes theenv
variable name and the transformer function.
Here is an example for both:
const config = {
useNewFeature: ['USE_NEW_FEATURE', trueOrFalse => trueOrFalse === 'true'], // results a boolean
serverHosts: ['SERVER_HOSTS', csvString => csvString.split(',')] // results in a string array
buildDate: transform('BUILD_DATE', dateString => new Date(dateString)) // results in a `Date` object
... //other env variables
}
module.exports = verify(config)
Functions passed to either transform
or given in a TransformTuple
will not be run if its corresponding env value is missing.
A transformFP
function is also provided that accepts the transforming function first and will return a partially applied function if an environment key string is not supplied:
import { transformFP, verify } from 'env-verifier'
const parseBoolean = transformFP(trueOrFalse => trueOrFalse === 'true')
export const config = verify({
useNewFeature: parseBoolean('USE_NEW_FEATURE'), // results in a boolean value
hosts: transformFP(csvList => csvList.split(','), 'HOSTS') // results in a string array
... other values
})
Dynamic Typings
Important
As of v1.4.0
, env-verifier
should now be able to correctly and dynamically infer the return types of both verify
and strictVerify
without any extra help. the below is only valid for versions that pre-date v1.4.0
env-verifier
tries to give typescript typings for the config object that it returns, but needs a little help to get the correct types
If you are using TypeScript, you can do the following:
const config: {
a: 'A',
b: insert([1, 2])
c: {
d: ['A', (envValue) => ([envValue])]
}
}
const verifiedConfig = strictVerify(config)
// pre-v1.4.0 typings:
// typeof verifiedConfig = {
// a: VerifiedConfig<unknown>
// b: VerifiedConfig<unknown>
// c: VerifiedConfig<unknown>
// }
// add typeof config object
const verifiedConfig = strictVerify<typeof config>(config)
// better typings:
// typeof verifiedConfig = {
// a: string,
// b: number[],
// c: {
// d: (string | (envVerify: any) => any)
// }
// }
// cast TransformTuple types correctly
const config = {
a: 'A',
b: insert([1, 2])
c: {
d: ['A', (envValue) => ([envValue])] as TransformTuple<string>
}
}
const verifiedConfig = strictVerify<typeof config>(config)
// best typings:
// typeof verifiedConfig = {
// a: string,
// b: number[],
// c: {
// d: string
// }
// }
env-verifier
vs convict
Mozilla produces the excellent convict
package that does most (if not all) of the same things that this package does. Here are a quick list of comparisons between the two:
|Feature|env-verifier
|convict
|
|-|-|-|
| Config Merging | ⚠️ | ✔️ |
| Nested Structures | ✔️ | ✔️ |
| Environmental Variables | ✔️ | ✔️ |
| Command-line arguments | ❌ | ✔️ |
| Validation | ✔️ | ✔️ |
| Secret Obfuscation | ✔️ | ✔️ |
convict
does more than what's included on the above list, and certainly more than env-verifier
can do; so, it may be the correct choice for your project, especially if your project is a large one with many different/changing contributors.
However env-verifier
excels in the following:
- Simplicity: Does one thing, and does it well
- Size: ~8kb packed, ~18kb unpacked, 4 source files total
- No production dependencies
Prerequisites
This package is written in [email protected] and is built/distributed for environments that support the majority of the es2016 specification.
This package also works best with projects that have centralized config files, IE: You map your .env
variables to a config
object in a file, and import
/require
that config object wherever you need .env
values.
Other than that, just install the package and get going!
One of these:
npm install env-verifier
And one of these:
const { verify, strictVerify } = require('env-verifier')
And you're all set.
Testing
After you've ran npm install
, just run npm test
.
We use jest as our testing framework.
Contributing
Please read CONTRIBUTING.md for details on our code of conduct, and the process for submitting pull requests to us.
Versioning
We use SemVer for versioning. For the versions available, see the tags on this repository.
Authors
- Snugbear - Initial work
See also the list of contributors who participated in this project.
License
This project is licensed under the MIT License - see the LICENSE file for details.