# VSCode JSON Language Server
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The JSON Language server provides language-specific smarts for editing, validating and understanding JSON documents. It runs as a separate executable and implements the [language server protocol](https://microsoft.github.io/language-server-protocol/overview) to be connected by any code editor or IDE.
## Capabilities
### Server capabilities
The JSON language server supports requests on documents of language id `json` and `jsonc`.
- `json` documents are parsed and validated following the [JSON specification](https://tools.ietf.org/html/rfc7159).
- `jsonc` documents additionally accept single line (`//`) and multi-line comments (`/* ... */`). JSONC is a VSCode specific file format, intended for VSCode configuration files, without any aspirations to define a new common file format.
The server implements the following capabilities of the language server protocol:
- [Code completion](https://microsoft.github.io/language-server-protocol/specification#textDocument_completion) for JSON properties and values based on the document's [JSON schema](http://json-schema.org/) or based on existing properties and values used at other places in the document. JSON schemas are configured through the server configuration options.
- [Hover](https://microsoft.github.io/language-server-protocol/specification#textDocument_hover) for values based on descriptions in the document's [JSON schema](http://json-schema.org/).
- [Document Symbols](https://microsoft.github.io/language-server-protocol/specification#textDocument_documentSymbol) for quick navigation to properties in the document.
- [Document Colors](https://microsoft.github.io/language-server-protocol/specification#textDocument_documentColor) for showing color decorators on values representing colors and [Color Presentation](https://microsoft.github.io/language-server-protocol/specification#textDocument_colorPresentation) for color presentation information to support color pickers. The location of colors is defined by the document's [JSON schema](http://json-schema.org/). All values marked with `"format": "color-hex"` (VSCode specific, non-standard JSON Schema extension) are considered color values. The supported color formats are `#rgb[a]` and `#rrggbb[aa]`.
- [Code Formatting](https://microsoft.github.io/language-server-protocol/specification#textDocument_rangeFormatting) supporting ranges and formatting the whole document.
- [Folding Ranges](https://microsoft.github.io/language-server-protocol/specification#textDocument_foldingRange) for all folding ranges in the document.
- Semantic Selection for semantic selection for one or multiple cursor positions.
- [Goto Definition](https://microsoft.github.io/language-server-protocol/specification#textDocument_definition) for $ref references in JSON schemas
- [Diagnostics (Validation)](https://microsoft.github.io/language-server-protocol/specification#textDocument_publishDiagnostics) are pushed for all open documents
- syntax errors
- structural validation based on the document's [JSON schema](http://json-schema.org/).
In order to load JSON schemas, the JSON server uses NodeJS `http` and `fs` modules. For all other features, the JSON server only relies on the documents and settings provided by the client through the LSP.
### Client requirements:
The JSON language server expects the client to only send requests and notifications for documents of language id `json` and `jsonc`.
The JSON language server has the following dependencies on the client's capabilities:
- Code completion requires that the client capability has *snippetSupport*. If not supported by the client, the server will not offer the completion capability.
- Formatting support requires the client to support *dynamicRegistration* for *rangeFormatting*. If not supported by the client, the server will not offer the format capability.
## Configuration
### Initialization options
The client can send the following initialization options to the server:
- `provideFormatter: boolean | undefined`. If defined, the value defines whether the server provides the `documentRangeFormattingProvider` capability on initialization. If undefined, the setting `json.format.enable` is used to determine whether formatting is provided. The formatter will then be registered through dynamic registration. If the client does not support dynamic registration, no formatter will be available.
- `handledSchemaProtocols`: The URI schemas handles by the server. See section `Schema configuration` below.
- `customCapabilities`: Additional non-LSP client capabilities:
- `rangeFormatting: { editLimit: x } }`: For performance reasons, limit the number of edits returned by the range formatter to `x`.
### Settings
Clients may send a `workspace/didChangeConfiguration` notification to notify the server of settings changes.
The server supports the following settings:
- http
- `proxy`: The URL of the proxy server to use when fetching schema. When undefined or empty, no proxy is used.
- `proxyStrictSSL`: Whether the proxy server certificate should be verified against the list of supplied CAs.
- json
- `format`
- `enable`: Whether the server should register the formatting support. This option is only applicable if the client supports *dynamicRegistration* for *rangeFormatting* and `initializationOptions.provideFormatter` is not defined.
- `schemas`: Configures association of file names to schema URL or schemas and/or associations of schema URL to schema content.
- `fileMatch`: an array of file names or paths (separated by `/`). `*` can be used as a wildcard. Exclusion patterns can also be defined and start with '!'. A file matches when there is at least one matching pattern and the last matching pattern is not an exclusion pattern.
- `url`: The URL of the schema, optional when also a schema is provided.
- `schema`: The schema content.
- `resultLimit`: The max number folding ranges and outline symbols to be computed (for performance reasons)
```json
{
"http": {
"proxy": "",
"proxyStrictSSL": true
},
"json": {
"format": {
"enable": true
},
"schemas": [
{
"fileMatch": [
"foo.json",
"*.superfoo.json"
],
"url": "http://json.schemastore.org/foo",
"schema": {
"type": "array"
}
}
]
}
}
```
### Schema configuration and custom schema content delivery
[JSON schemas](http://json-schema.org/) are essential for code assist, hovers, color decorators to work and are required for structural validation.
To find the schema for a given JSON document, the server uses the following mechanisms:
- JSON documents can define the schema URL using a `$schema` property
- The settings define a schema association based on the documents URL. Settings can either associate a schema URL to a file or path pattern, and they can directly provide a schema.
- Additionally, schema associations can also be provided by a custom 'schemaAssociations' configuration call.
Schemas are identified by URLs. To load the content of a schema, the JSON language server either tries to load from that URI or path itself or delegates to the client.
The `initializationOptions.handledSchemaProtocols` initialization option defines which URLs are handled by the server. Requests for all other URIs are sent to the client.