Language Server: Implement Folding Ranges

javascript/packages/language-server/src/folding_range_service.ts

@@ -0,0 +1,138 @@
+import { FoldingRange, FoldingRangeKind } from "vscode-languageserver/node"
+import { Visitor } from "@herb-tools/core"
+
+import type {
+  Node,
+  HTMLElementNode,
+  HTMLOpenTagNode,
+  HTMLAttributeValueNode,
+  HTMLCommentNode,
+  ERBIfNode,
+  ERBElseNode,
+  ERBUnlessNode,
+  ERBBlockNode,
+  ERBWhileNode,
+  ERBUntilNode,
+  ERBForNode,
+  ERBBeginNode,
+  DocumentNode,
+} from "@herb-tools/core"
+
+export class FoldingRangeService {
+  getFoldingRanges(document: DocumentNode): FoldingRange[] {
+    const collector = new FoldingRangeCollector()
+
+    collector.visit(document)
+
+    return collector.ranges
+  }
+}
+
+/**
+ * Visitor that collects foldable ranges from the AST
+ */
+class FoldingRangeCollector extends Visitor {
+  ranges: FoldingRange[] = []
+
+  visitHTMLElementNode(node: HTMLElementNode): void {
+    this.addRangeForNode(node, node.body)
+    this.visitChildNodes(node)
+  }
+
+  visitHTMLOpenTagNode(node: HTMLOpenTagNode): void {
+    this.addRangeForNode(node, node.children)
+    this.visitChildNodes(node)
+  }
+
+  visitHTMLCommentNode(node: HTMLCommentNode): void {
+    const startLine = this.toZeroBased(node.location.start.line)
+    const endLine = this.toZeroBased(node.location.end.line)
+
+    this.addRange(startLine, endLine, FoldingRangeKind.Comment)
+
+    this.visitChildNodes(node)
+  }
+
+  visitHTMLAttributeValueNode(node: HTMLAttributeValueNode): void {
+    this.addRangeForNode(node, node.children)
+    this.visitChildNodes(node)
+  }
+
+  visitERBIfNode(node: ERBIfNode): void {
+    const startLine = this.toZeroBased(node.location.start.line)
+    const endLine = this.toZeroBased(node.location.end.line)
+
+    this.addRange(startLine, endLine)
+
+    if (node.statements.length > 0) {
+      const firstStatement = node.statements[0]
+      const lastStatement = node.statements[node.statements.length - 1]
+
+      const startLine = this.toZeroBased(firstStatement.location.start.line)
+      const endLine = this.toZeroBased(lastStatement.location.end.line)
+
+      this.addRange(startLine, endLine)
+    }
+
+    this.visitChildNodes(node)
+  }
+
+  visitERBElseNode(node: ERBElseNode): void {
+    this.addRangeForNode(node, node.statements)
+    this.visitChildNodes(node)
+  }
+
+  visitERBUnlessNode(node: ERBUnlessNode): void {
+    this.addRangeForNode(node, node.statements)
+    this.visitChildNodes(node)
+  }
+
+  visitERBBlockNode(node: ERBBlockNode): void {
+    this.addRangeForNode(node, node.body)
+    this.visitChildNodes(node)
+  }
+
+  visitERBWhileNode(node: ERBWhileNode): void {
+    this.addRangeForNode(node, node.statements)
+    this.visitChildNodes(node)
+  }
+
+  visitERBUntilNode(node: ERBUntilNode): void {
+    this.addRangeForNode(node, node.statements)
+    this.visitChildNodes(node)
+  }
+
+  visitERBForNode(node: ERBForNode): void {
+    this.addRangeForNode(node, node.statements)
+    this.visitChildNodes(node)
+  }
+
+  visitERBBeginNode(node: ERBBeginNode): void {
+    this.addRangeForNode(node, node.statements)
+    this.visitChildNodes(node)
+  }
+
+  // TODO: consider adding `startCharacter` and `endCharacter`
+  private addRange(startLine: number, endLine: number, kind?: FoldingRangeKind): void {
+    if (endLine > startLine) {
+      this.ranges.push({
+        startLine,
+        endLine,
+        kind,
+      })
+    }
+  }
+
+  private addRangeForNode(node: Node, children: Node[]) {
+    if (children.length > 0) {
+      const startLine = this.toZeroBased(node.location.start.line)
+      const endLine = this.toZeroBased(node.location.end.line)
+
+      this.addRange(startLine, endLine)
+    }
+  }
+
+  private toZeroBased(line: number): number {
+    return line - 1
+  }
+}

javascript/packages/language-server/src/index.ts

@@ -3,6 +3,7 @@ export * from "./service"
 export * from "./diagnostics"
 export * from "./document_service"
 export * from "./formatting_service"
+export * from "./folding_range_service"
 export * from "./project"
 export * from "./settings"
 export * from "./utils"

javascript/packages/language-server/src/server.ts

@@ -12,6 +12,8 @@ import {
   DocumentRangeFormattingParams,
   CodeActionParams,
   CodeActionKind,
+  TextEdit,
+  FoldingRangeParams,
 } from "vscode-languageserver/node"
 
 import { Service } from "./service"
@@ -53,6 +55,7 @@ export class Server {
           codeActionProvider: {
             codeActionKinds: [CodeActionKind.QuickFix, CodeActionKind.SourceFixAll]
           },
+          foldingRangeProvider: true,
         },
       }
 
@@ -175,6 +178,16 @@ export class Server {
 
       return autofixCodeActions.concat(linterDisableCodeActions)
     })
+
+    this.connection.onFoldingRanges((params: FoldingRangeParams) => {
+      const document = this.service.documentService.get(params.textDocument.uri)
+
+      if (!document) return []
+
+      const parseResult = this.service.parserService.parseDocument(document)
+
+      return this.service.foldingRangeService.getFoldingRanges(parseResult.document)
+    })
   }
 
   listen() {

javascript/packages/language-server/src/service.ts

@@ -12,6 +12,7 @@ import { ConfigService } from "./config_service"
 import { AutofixService } from "./autofix_service"
 import { CodeActionService } from "./code_action_service"
 import { DocumentSaveService } from "./document_save_service"
+import { FoldingRangeService } from "./folding_range_service"
 
 import { version } from "../package.json"
 
@@ -30,6 +31,7 @@ export class Service {
   configService: ConfigService
   codeActionService: CodeActionService
   documentSaveService: DocumentSaveService
+  foldingRangeService: FoldingRangeService
 
   constructor(connection: Connection, params: InitializeParams) {
     this.connection = connection
@@ -44,6 +46,7 @@ export class Service {
     this.codeActionService = new CodeActionService(this.project, this.config)
     this.diagnostics = new Diagnostics(this.connection, this.documentService, this.parserService, this.linterService, this.configService)
     this.documentSaveService = new DocumentSaveService(this.connection, this.settings, this.autofixService, this.formattingService)
+    this.foldingRangeService = new FoldingRangeService()
 
     if (params.initializationOptions) {
       this.settings.globalSettings = params.initializationOptions as PersonalHerbSettings