Add hover syntax highlighting for types

.changeset/real-boxes-clap.md

@@ -0,0 +1,7 @@
+---
+'graphql-language-service': patch
+'graphql-language-service-interface': patch
+'graphql-language-service-server': patch
+---
+
+Add an opt-in feature to generate markdown in hover elements, starting with highlighting type information. Enabled for the language server and also the language service and thus `monaco-graphql` as well.

packages/graphql-language-service-interface/src/GraphQLLanguageService.ts

@@ -35,7 +35,7 @@ import {
 
 import { Kind, parse, print } from 'graphql';
 import { getAutocompleteSuggestions } from './getAutocompleteSuggestions';
-import { getHoverInformation } from './getHoverInformation';
+import { getHoverInformation, HoverConfig } from './getHoverInformation';
 import { validateQuery, getRange, DIAGNOSTIC_SEVERITY } from './getDiagnostics';
 import {
   getDefinitionQueryResultForFragmentSpread,
@@ -250,12 +250,13 @@ export class GraphQLLanguageService {
     query: string,
     position: IPosition,
     filePath: Uri,
+    options?: HoverConfig,
   ): Promise<Hover['contents']> {
     const projectConfig = this.getConfigForURI(filePath);
     const schema = await this._graphQLCache.getSchema(projectConfig.name);
 
     if (schema) {
-      return getHoverInformation(schema, query, position);
+      return getHoverInformation(schema, query, position, undefined, options);
     }
     return '';
   }

packages/graphql-language-service-interface/src/getHoverInformation.ts

@@ -26,11 +26,14 @@ import { AllTypeInfo, IPosition } from 'graphql-language-service-types';
 import { Hover } from 'vscode-languageserver-types';
 import { getTokenAtPosition, getTypeInfo } from './getAutocompleteSuggestions';
 
+export type HoverConfig = { useMarkdown?: boolean };
+
 export function getHoverInformation(
   schema: GraphQLSchema,
   queryText: string,
   cursor: IPosition,
   contextToken?: ContextToken,
+  config?: HoverConfig,
 ): Hover['contents'] {
   const token = contextToken || getTokenAtPosition(queryText, cursor);
 
@@ -42,7 +45,7 @@ export function getHoverInformation(
   const kind = state.kind;
   const step = state.step;
   const typeInfo = getTypeInfo(schema, token.state);
-  const options = { schema };
+  const options = { ...config, schema };
 
   // Given a Schema and a Token, produce the contents of an info tooltip.
   // To do this, create a div element that we will render "into" and then pass
@@ -52,17 +55,23 @@ export function getHoverInformation(
     (kind === 'AliasedField' && step === 2 && typeInfo.fieldDef)
   ) {
     const into: string[] = [];
+    renderMdCodeStart(into, options);
     renderField(into, typeInfo, options);
+    renderMdCodeEnd(into, options);
     renderDescription(into, options, typeInfo.fieldDef);
     return into.join('').trim();
   } else if (kind === 'Directive' && step === 1 && typeInfo.directiveDef) {
     const into: string[] = [];
+    renderMdCodeStart(into, options);
     renderDirective(into, typeInfo, options);
+    renderMdCodeEnd(into, options);
     renderDescription(into, options, typeInfo.directiveDef);
     return into.join('').trim();
   } else if (kind === 'Argument' && step === 0 && typeInfo.argDef) {
     const into: string[] = [];
+    renderMdCodeStart(into, options);
     renderArg(into, typeInfo, options);
+    renderMdCodeEnd(into, options);
     renderDescription(into, options, typeInfo.argDef);
     return into.join('').trim();
   } else if (
@@ -71,7 +80,9 @@ export function getHoverInformation(
     'description' in typeInfo.enumValue
   ) {
     const into: string[] = [];
+    renderMdCodeStart(into, options);
     renderEnumValue(into, typeInfo, options);
+    renderMdCodeEnd(into, options);
     renderDescription(into, options, typeInfo.enumValue);
     return into.join('').trim();
   } else if (
@@ -80,13 +91,26 @@ export function getHoverInformation(
     'description' in typeInfo.type
   ) {
     const into: string[] = [];
+    renderMdCodeStart(into, options);
     renderType(into, typeInfo, options, typeInfo.type);
+    renderMdCodeEnd(into, options);
     renderDescription(into, options, typeInfo.type);
     return into.join('').trim();
   }
   return '';
 }
 
+function renderMdCodeStart(into: string[], options: any) {
+  if (options.useMarkdown) {
+    text(into, '```graphql\n');
+  }
+}
+function renderMdCodeEnd(into: string[], options: any) {
+  if (options.useMarkdown) {
+    text(into, '\n```');
+  }
+}
+
 function renderField(into: string[], typeInfo: AllTypeInfo, options: any) {
   renderQualifiedField(into, typeInfo, options);
   renderTypeAnnotation(into, typeInfo, options, typeInfo.type as GraphQLType);
@@ -168,6 +192,7 @@ function renderType(
   if (!t) {
     return;
   }
+
   if (t instanceof GraphQLNonNull) {
     renderType(into, typeInfo, options, t.ofType);
     text(into, '!');

packages/graphql-language-service-server/src/MessageProcessor.ts

@@ -549,6 +549,7 @@ export class MessageProcessor {
       query,
       toPosition(position),
       textDocument.uri,
+      { useMarkdown: true },
     );
 
     return {

packages/graphql-language-service/src/LanguageService.ts

@@ -25,6 +25,7 @@ import {
   SchemaResponse,
   defaultSchemaBuilder,
 } from './schemaLoader';
+import { HoverConfig } from 'graphql-language-service-interface/src/getHoverInformation';
 
 export type GraphQLLanguageConfig = {
   parser?: typeof parse;
@@ -203,10 +204,13 @@ export class LanguageService {
     _uri: string,
     documentText: string,
     position: IPosition,
+    options?: HoverConfig,
   ) =>
     getHoverInformation(
       (await this.getSchema()) as GraphQLSchema,
       documentText,
       position,
+      undefined,
+      { useMarkdown: true, ...options },
     );
 }