REPL tab completion

src/bin.ts

@@ -2,14 +2,16 @@
 
 import { join, resolve, dirname } from 'path'
 import { start, Recoverable } from 'repl'
-import { inspect } from 'util'
+import { inspect, callbackify } from 'util'
 import Module = require('module')
 import arg = require('arg')
 import { diffLines } from 'diff'
 import { Script } from 'vm'
 import { readFileSync, statSync, realpathSync } from 'fs'
 import { homedir } from 'os'
 import { VERSION, TSError, parse, Register, register } from './index'
+import { CompleterResult } from 'readline'
+import { compare } from 'semver'
 
 /**
  * Eval filename for REPL/debug.
@@ -366,7 +368,10 @@ function startRepl (service: Register, state: EvalState, code?: string) {
     // Mimicking node's REPL implementation: https://github.com/nodejs/node/blob/168b22ba073ee1cbf8d0bcb4ded7ff3099335d04/lib/internal/repl.js#L28-L30
     terminal: process.stdout.isTTY && !parseInt(process.env.NODE_NO_READLINE!, 10),
     eval: replEval,
-    useGlobal: true
+    useGlobal: true,
+    completer: completer,
+    // completer: callbackify(asyncCompleter),
+    preview: true
   })
 
   /**
@@ -400,6 +405,16 @@ function startRepl (service: Register, state: EvalState, code?: string) {
     return callback(err, result)
   }
 
+  function completer(input: string): CompleterResult {
+    const undo = appendEval(state, input)
+    const { completions, context } = service.getCompletions(state.input, state.path, state.input.length)
+    undo()
+    return [completions, context]
+  }
+  async function asyncCompleter(line: string): Promise<CompleterResult> {
+    return [['prefixfoo', 'prefixbar', 'prefixbaz'], line]
+  }
+
   // Bookmark the point where we should reset the REPL state.
   const resetEval = appendEval(state, '')
 

src/index.ts

@@ -262,6 +262,11 @@ export interface TypeInfo {
   comment: string
 }
 
+export interface Completions {
+  completions: string[],
+  context: string
+}
+
 /**
  * Default register options, including values specified via environment
  * variables.
@@ -349,6 +354,7 @@ export interface Register {
   ignored (fileName: string): boolean
   compile (code: string, fileName: string, lineOffset?: number): string
   getTypeInfo (code: string, fileName: string, position: number): TypeInfo
+  getCompletions (code: string, fileName: string, position: number): Completions
 }
 
 /**
@@ -514,6 +520,15 @@ export function create (rawOptions: CreateOptions = {}): Register {
    */
   let getOutput: (code: string, fileName: string) => SourceOutput
   let getTypeInfo: (_code: string, _fileName: string, _position: number) => TypeInfo
+  let getCompletions: (_code: string, _fileName: string, _position: number) => Completions
+
+  const getEmptyCompletions = (code: string, fileName: string, position: number) => {
+    // throw new Error('not implemented')
+    return {
+      completions: [],
+      context: ''
+    }
+  }
 
   // Use full language services when the fast option is disabled.
   if (!transpileOnly) {
@@ -648,6 +663,20 @@ export function create (rawOptions: CreateOptions = {}): Register {
 
         return { name, comment }
       }
+
+      getCompletions = (code: string, fileName: string, position: number) => {
+        updateMemoryCache(code, fileName)
+
+        // https://github.com/microsoft/monaco-typescript/blob/e623bb9f76c8376b433e7f1c30fec5a5d7abd4d1/src/languageFeatures.ts#L274-L309
+        const trailingWordLength = code.slice(0, position).match(/\s*[a-zA-Z0-9_$]+\s*$/)?.[0].length ?? 0
+
+        const info = service.getCompletionsAtPosition(fileName, position, {includeCompletionsWithInsertText: true})
+        const entries = info?.entries.filter(entry => !entry.hasAction && !entry.replacementSpan) ?? []
+        return {
+          completions: entries.map(entry => entry.name),
+          context: code.slice(position - trailingWordLength, position)
+        }
+      }
     } else {
       const sys = {
         ...ts.sys,
@@ -791,6 +820,8 @@ export function create (rawOptions: CreateOptions = {}): Register {
         }
       }
 
+      getCompletions = getEmptyCompletions
+
       // Write `.tsbuildinfo` when `--build` is enabled.
       if (options.emit && config.options.incremental) {
         process.on('exit', () => {
@@ -821,6 +852,8 @@ export function create (rawOptions: CreateOptions = {}): Register {
     getTypeInfo = () => {
       throw new TypeError('Type information is unavailable in "--transpile-only"')
     }
+
+    getCompletions = getEmptyCompletions
   }
 
   // Create a simple TypeScript compiler proxy.
@@ -845,7 +878,7 @@ export function create (rawOptions: CreateOptions = {}): Register {
     return true
   }
 
-  return { ts, config, compile, getTypeInfo, ignored, enabled, options }
+  return { ts, config, compile, getTypeInfo, getCompletions, ignored, enabled, options }
 }
 
 /**