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228 lines
5.8 KiB
Markdown
228 lines
5.8 KiB
Markdown
5 years ago
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# rc
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The non-configurable configuration loader for lazy people.
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## Usage
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The only option is to pass rc the name of your app, and your default configuration.
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```javascript
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var conf = require('rc')(appname, {
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//defaults go here.
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port: 2468,
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//defaults which are objects will be merged, not replaced
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views: {
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engine: 'jade'
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}
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});
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```
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`rc` will return your configuration options merged with the defaults you specify.
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If you pass in a predefined defaults object, it will be mutated:
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```javascript
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var conf = {};
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require('rc')(appname, conf);
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```
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If `rc` finds any config files for your app, the returned config object will have
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a `configs` array containing their paths:
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```javascript
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var appCfg = require('rc')(appname, conf);
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appCfg.configs[0] // /etc/appnamerc
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appCfg.configs[1] // /home/dominictarr/.config/appname
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appCfg.config // same as appCfg.configs[appCfg.configs.length - 1]
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```
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## Standards
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Given your application name (`appname`), rc will look in all the obvious places for configuration.
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* command line arguments, parsed by minimist _(e.g. `--foo baz`, also nested: `--foo.bar=baz`)_
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* environment variables prefixed with `${appname}_`
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* or use "\_\_" to indicate nested properties <br/> _(e.g. `appname_foo__bar__baz` => `foo.bar.baz`)_
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* if you passed an option `--config file` then from that file
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* a local `.${appname}rc` or the first found looking in `./ ../ ../../ ../../../` etc.
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* `$HOME/.${appname}rc`
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* `$HOME/.${appname}/config`
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* `$HOME/.config/${appname}`
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* `$HOME/.config/${appname}/config`
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* `/etc/${appname}rc`
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* `/etc/${appname}/config`
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* the defaults object you passed in.
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All configuration sources that were found will be flattened into one object,
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so that sources **earlier** in this list override later ones.
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## Configuration File Formats
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Configuration files (e.g. `.appnamerc`) may be in either [json](http://json.org/example) or [ini](http://en.wikipedia.org/wiki/INI_file) format. **No** file extension (`.json` or `.ini`) should be used. The example configurations below are equivalent:
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#### Formatted as `ini`
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```
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; You can include comments in `ini` format if you want.
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dependsOn=0.10.0
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; `rc` has built-in support for ini sections, see?
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[commands]
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www = ./commands/www
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console = ./commands/repl
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; You can even do nested sections
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[generators.options]
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engine = ejs
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[generators.modules]
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new = generate-new
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engine = generate-backend
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```
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#### Formatted as `json`
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```javascript
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{
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// You can even comment your JSON, if you want
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"dependsOn": "0.10.0",
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"commands": {
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"www": "./commands/www",
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"console": "./commands/repl"
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},
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"generators": {
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"options": {
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"engine": "ejs"
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},
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"modules": {
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"new": "generate-new",
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"backend": "generate-backend"
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}
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}
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}
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```
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Comments are stripped from JSON config via [strip-json-comments](https://github.com/sindresorhus/strip-json-comments).
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> Since ini, and env variables do not have a standard for types, your application needs be prepared for strings.
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To ensure that string representations of booleans and numbers are always converted into their proper types (especially useful if you intend to do strict `===` comparisons), consider using a module such as [parse-strings-in-object](https://github.com/anselanza/parse-strings-in-object) to wrap the config object returned from rc.
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## Simple example demonstrating precedence
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Assume you have an application like this (notice the hard-coded defaults passed to rc):
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```
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const conf = require('rc')('myapp', {
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port: 12345,
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mode: 'test'
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});
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console.log(JSON.stringify(conf, null, 2));
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```
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You also have a file `config.json`, with these contents:
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```
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{
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"port": 9000,
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"foo": "from config json",
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"something": "else"
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}
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```
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And a file `.myapprc` in the same folder, with these contents:
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```
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{
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"port": "3001",
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"foo": "bar"
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}
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```
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Here is the expected output from various commands:
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`node .`
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```
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{
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"port": "3001",
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"mode": "test",
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"foo": "bar",
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"_": [],
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"configs": [
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"/Users/stephen/repos/conftest/.myapprc"
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],
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"config": "/Users/stephen/repos/conftest/.myapprc"
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}
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```
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*Default `mode` from hard-coded object is retained, but port is overridden by `.myapprc` file (automatically found based on appname match), and `foo` is added.*
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`node . --foo baz`
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```
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{
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"port": "3001",
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"mode": "test",
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"foo": "baz",
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"_": [],
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"configs": [
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"/Users/stephen/repos/conftest/.myapprc"
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],
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"config": "/Users/stephen/repos/conftest/.myapprc"
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}
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```
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*Same result as above but `foo` is overridden because command-line arguments take precedence over `.myapprc` file.*
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`node . --foo barbar --config config.json`
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```
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{
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"port": 9000,
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"mode": "test",
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"foo": "barbar",
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"something": "else",
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"_": [],
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"config": "config.json",
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"configs": [
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"/Users/stephen/repos/conftest/.myapprc",
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"config.json"
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]
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}
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```
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*Now the `port` comes from the `config.json` file specified (overriding the value from `.myapprc`), and `foo` value is overriden by command-line despite also being specified in the `config.json` file.*
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## Advanced Usage
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#### Pass in your own `argv`
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You may pass in your own `argv` as the third argument to `rc`. This is in case you want to [use your own command-line opts parser](https://github.com/dominictarr/rc/pull/12).
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```javascript
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require('rc')(appname, defaults, customArgvParser);
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```
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## Pass in your own parser
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If you have a special need to use a non-standard parser,
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you can do so by passing in the parser as the 4th argument.
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(leave the 3rd as null to get the default args parser)
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```javascript
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require('rc')(appname, defaults, null, parser);
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```
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This may also be used to force a more strict format,
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such as strict, valid JSON only.
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## Note on Performance
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`rc` is running `fs.statSync`-- so make sure you don't use it in a hot code path (e.g. a request handler)
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## License
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Multi-licensed under the two-clause BSD License, MIT License, or Apache License, version 2.0
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