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`.
-`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.
- [Diagnostics (Validation)](https://microsoft.github.io/language-server-protocol/specification#textDocument_publishDiagnostics) are pushed for all open documents
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.
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.
-`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.
-`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.
-`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.
- 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.
Requests for schemas with URLs not handled by the server are forwarded to the client through an LSP request. This request is a JSON language server-specific, non-standardized, extension to the LSP.
When the client is aware that a schema content has changed, it will notify the server through a notification. This notification is a JSON language server-specific, non-standardized, extension to the LSP.
In addition to the settings, schemas associations can also be provided through a notification from the client to the server. This notification is a JSON language server-specific, non-standardized, extension to the LSP.
The JSON language server is shipped with [Visual Studio Code](https://code.visualstudio.com/) as part of the built-in VSCode extension `json-language-features`. The server is started when the first JSON file is opened. The [VSCode JSON documentation](https://code.visualstudio.com/docs/languages/json) for detailed information on the user experience and has more information on how to configure the language support.
If you plan to integrate the JSON language server into an editor and IDE, check out [this page](https://microsoft.github.io/language-server-protocol/implementors/tools/) if there's already an LSP client integration available.
To connect to the server from NodeJS, see Remy Suen's great write-up on [how to communicate with the server](https://github.com/rcjsuen/dockerfile-language-server-nodejs#communicating-with-the-server) through the available communication channels.
The source code of the JSON language server can be found in the [VSCode repository](https://github.com/microsoft/vscode) at [extensions/json-language-features/server](https://github.com/microsoft/vscode/tree/master/extensions/json-language-features/server).
File issues and pull requests in the [VSCode GitHub Issues](https://github.com/microsoft/vscode/issues). See the document [How to Contribute](https://github.com/microsoft/vscode/wiki/How-to-Contribute) on how to build and run from source.
- [jsonc-parser](https://github.com/microsoft/node-jsonc-parser) contains the JSON parser and scanner.
- [vscode-json-languageservice](https://github.com/microsoft/vscode-json-languageservice) contains the implementation of all features as a re-usable library.
- [vscode-languageserver-node](https://github.com/microsoft/vscode-languageserver-node) contains the implementation of language server for NodeJS.
This project has adopted the [Microsoft Open Source Code of Conduct](https://opensource.microsoft.com/codeofconduct/). For more information see the [Code of Conduct FAQ](https://opensource.microsoft.com/codeofconduct/faq/) or contact [opencode@microsoft.com](mailto:opencode@microsoft.com) with any additional questions or comments.