Make ts-node eval public for node REPL consumption (#1121)

* Add createReplEval function

* Add a test

* Fix a couple of typos

* Actually test the evaluator

* Try removing spec

* Use service creation pattern

* Move REPL code to its own file

* - Reorder repl.ts declarations to match the original order from bin.ts
- promote createReplService to top of the file since it will hopefully be the
main entrypoint to any REPL functionality

* Expand ReplService API; use new API in bin.ts, which further decouples bin.ts from repl.ts

* Add brief, internal docs for REPL API

* Add support for DI of alternative stdio streams into REPL

* export REPL from index.ts

* remove unnecessary export

* Add test for new REPL API

* API surface, naming, docs tweaks

* tweak identifiers

* fix name

* Tweak repl API test to match REPL CLI test, allowing it to pass on Windows

Co-authored-by: Andrew Bradley <[email protected]>

Author: MarcManiez

development-docs/repl-api.md

@@ -0,0 +1,27 @@
+## How to create your own ts-node powered REPL
+
+- Create ts-node REPL service which includes EvalState
+- Create ts-node compiler service using EvalState-aware `readFile` and `fileExists` implementations from REPL
+- Bind REPL service to compiler service (chicken-and-egg problem necessitates late binding)
+- Either:
+  - call REPL method start() to start a REPL
+  - create your own node repl but pass it REPL service's nodeEval() function
+
+```
+import * as tsnode from 'ts-node';
+const repl = tsnode.createRepl();
+const service = tsnode.register({
+    ... options,
+    ...repl.evalAwarePartialHost
+});
+repl.setService(service);
+
+// Start it
+repl.start();
+
+// or
+const nodeRepl = require('repl').start({
+    ...options,
+    eval: repl.nodeEval
+});
+```

package-lock.json

@@ -92,6 +92,7 @@
     "@types/source-map-support": "^0.5.0",
     "axios": "^0.19.0",
     "chai": "^4.0.1",
+    "get-stream": "^6.0.0",
     "lodash": "^4.17.15",
     "mocha": "^6.2.2",
     "ntypescript": "^1.201507091536.1",

package.json

@@ -1,32 +1,16 @@
 #!/usr/bin/env node
 
 import { join, resolve, dirname } from 'path'
-import { start, Recoverable } from 'repl'
 import { inspect } 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, Service, register } from './index'
-
-/**
- * Eval filename for REPL/debug.
- */
-const EVAL_FILENAME = `[eval].ts`
-
-/**
- * Eval state management.
- */
-class EvalState {
-  input = ''
-  output = ''
-  version = 0
-  lines = 0
-
-  constructor (public path: string) {}
-}
+import {
+  EVAL_FILENAME,
+  EvalState,
+  createRepl,
+  ReplService
+ } from './repl'
+import { VERSION, TSError, parse, register } from './index'
 
 /**
  * Main `bin` functionality.
@@ -160,6 +144,8 @@ export function main (argv: string[] = process.argv.slice(2), entrypointArgs: Re
   /** Unresolved.  May point to a symlink, not realpath.  May be missing file extension */
   const scriptPath = args._.length ? resolve(cwd, args._[0]) : undefined
   const state = new EvalState(scriptPath || join(cwd, EVAL_FILENAME))
+  const replService = createRepl({ state })
+  const { evalAwarePartialHost } = replService
 
   // Register the TypeScript compiler instance.
   const service = register({
@@ -180,29 +166,13 @@ export function main (argv: string[] = process.argv.slice(2), entrypointArgs: Re
     ignoreDiagnostics,
     compilerOptions,
     require: argsRequire,
-    readFile: code !== undefined
-      ? (path: string) => {
-        if (path === state.path) return state.input
-
-        try {
-          return readFileSync(path, 'utf8')
-        } catch (err) {/* Ignore. */}
-      }
-      : undefined,
-    fileExists: code !== undefined
-      ? (path: string) => {
-        if (path === state.path) return true
-
-        try {
-          const stats = statSync(path)
-          return stats.isFile() || stats.isFIFO()
-        } catch (err) {
-          return false
-        }
-      }
-      : undefined
+    readFile: code !== undefined ? evalAwarePartialHost.readFile : undefined,
+    fileExists: code !== undefined ? evalAwarePartialHost.fileExists : undefined
   })
 
+  // Bind REPL service to ts-node compiler service (chicken-and-egg problem)
+  replService.setService(service)
+
   // Output project information.
   if (version >= 2) {
     console.log(`ts-node v${VERSION}`)
@@ -222,19 +192,19 @@ export function main (argv: string[] = process.argv.slice(2), entrypointArgs: Re
 
   // Execute the main contents (either eval, script or piped).
   if (code !== undefined && !interactive) {
-    evalAndExit(service, state, module, code, print)
+    evalAndExit(replService, module, code, print)
   } else {
     if (args._.length) {
       Module.runMain()
     } else {
       // Piping of execution _only_ occurs when no other script is specified.
       // --interactive flag forces REPL
       if (interactive || process.stdin.isTTY) {
-        startRepl(service, state, code)
+        replService.start(code)
       } else {
         let buffer = code || ''
         process.stdin.on('data', (chunk: Buffer) => buffer += chunk)
-        process.stdin.on('end', () => evalAndExit(service, state, module, buffer, print))
+        process.stdin.on('end', () => evalAndExit(replService, module, buffer, print))
       }
     }
   }
@@ -284,7 +254,7 @@ function getCwd (dir?: string, scriptMode?: boolean, scriptPath?: string) {
 /**
  * Evaluate a script.
  */
-function evalAndExit (service: Service, state: EvalState, module: Module, code: string, isPrinted: boolean) {
+function evalAndExit (replService: ReplService, module: Module, code: string, isPrinted: boolean) {
   let result: any
 
   ;(global as any).__filename = module.filename
@@ -294,7 +264,7 @@ function evalAndExit (service: Service, state: EvalState, module: Module, code:
   ;(global as any).require = module.require.bind(module)
 
   try {
-    result = _eval(service, state, code)
+    result = replService.evalCode(code)
   } catch (error) {
     if (error instanceof TSError) {
       console.error(error)
@@ -309,203 +279,6 @@ function evalAndExit (service: Service, state: EvalState, module: Module, code:
   }
 }
 
-/**
- * Evaluate the code snippet.
- */
-function _eval (service: Service, state: EvalState, input: string) {
-  const lines = state.lines
-  const isCompletion = !/\n$/.test(input)
-  const undo = appendEval(state, input)
-  let output: string
-
-  try {
-    output = service.compile(state.input, state.path, -lines)
-  } catch (err) {
-    undo()
-    throw err
-  }
-
-  // Use `diff` to check for new JavaScript to execute.
-  const changes = diffLines(state.output, output)
-
-  if (isCompletion) {
-    undo()
-  } else {
-    state.output = output
-  }
-
-  return changes.reduce((result, change) => {
-    return change.added ? exec(change.value, state.path) : result
-  }, undefined)
-}
-
-/**
- * Execute some code.
- */
-function exec (code: string, filename: string) {
-  const script = new Script(code, { filename: filename })
-
-  return script.runInThisContext()
-}
-
-/**
- * Start a CLI REPL.
- */
-function startRepl (service: Service, state: EvalState, code?: string) {
-  // Eval incoming code before the REPL starts.
-  if (code) {
-    try {
-      _eval(service, state, `${code}\n`)
-    } catch (err) {
-      console.error(err)
-      process.exit(1)
-    }
-  }
-
-  const repl = start({
-    prompt: '> ',
-    input: process.stdin,
-    output: process.stdout,
-    // 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
-  })
-
-  /**
-   * Eval code from the REPL.
-   */
-  function replEval (code: string, _context: any, _filename: string, callback: (err: Error | null, result?: any) => any) {
-    let err: Error | null = null
-    let result: any
-
-    // TODO: Figure out how to handle completion here.
-    if (code === '.scope') {
-      callback(err)
-      return
-    }
-
-    try {
-      result = _eval(service, state, code)
-    } catch (error) {
-      if (error instanceof TSError) {
-        // Support recoverable compilations using >= node 6.
-        if (Recoverable && isRecoverable(error)) {
-          err = new Recoverable(error)
-        } else {
-          console.error(error)
-        }
-      } else {
-        err = error
-      }
-    }
-
-    return callback(err, result)
-  }
-
-  // Bookmark the point where we should reset the REPL state.
-  const resetEval = appendEval(state, '')
-
-  function reset () {
-    resetEval()
-
-    // Hard fix for TypeScript forcing `Object.defineProperty(exports, ...)`.
-    exec('exports = module.exports', state.path)
-  }
-
-  reset()
-  repl.on('reset', reset)
-
-  repl.defineCommand('type', {
-    help: 'Check the type of a TypeScript identifier',
-    action: function (identifier: string) {
-      if (!identifier) {
-        repl.displayPrompt()
-        return
-      }
-
-      const undo = appendEval(state, identifier)
-      const { name, comment } = service.getTypeInfo(state.input, state.path, state.input.length)
-
-      undo()
-
-      if (name) repl.outputStream.write(`${name}\n`)
-      if (comment) repl.outputStream.write(`${comment}\n`)
-      repl.displayPrompt()
-    }
-  })
-
-  // Set up REPL history when available natively via node.js >= 11.
-  if (repl.setupHistory) {
-    const historyPath = process.env.TS_NODE_HISTORY || join(homedir(), '.ts_node_repl_history')
-
-    repl.setupHistory(historyPath, err => {
-      if (!err) return
-
-      console.error(err)
-      process.exit(1)
-    })
-  }
-}
-
-/**
- * Append to the eval instance and return an undo function.
- */
-function appendEval (state: EvalState, input: string) {
-  const undoInput = state.input
-  const undoVersion = state.version
-  const undoOutput = state.output
-  const undoLines = state.lines
-
-  // Handle ASI issues with TypeScript re-evaluation.
-  if (undoInput.charAt(undoInput.length - 1) === '\n' && /^\s*[\/\[(`-]/.test(input) && !/;\s*$/.test(undoInput)) {
-    state.input = `${state.input.slice(0, -1)};\n`
-  }
-
-  state.input += input
-  state.lines += lineCount(input)
-  state.version++
-
-  return function () {
-    state.input = undoInput
-    state.output = undoOutput
-    state.version = undoVersion
-    state.lines = undoLines
-  }
-}
-
-/**
- * Count the number of lines.
- */
-function lineCount (value: string) {
-  let count = 0
-
-  for (const char of value) {
-    if (char === '\n') {
-      count++
-    }
-  }
-
-  return count
-}
-
-const RECOVERY_CODES: Set<number> = new Set([
-  1003, // "Identifier expected."
-  1005, // "')' expected."
-  1109, // "Expression expected."
-  1126, // "Unexpected end of text."
-  1160, // "Unterminated template literal."
-  1161, // "Unterminated regular expression literal."
-  2355 // "A function whose declared type is neither 'void' nor 'any' must return a value."
-])
-
-/**
- * Check if a function can recover gracefully.
- */
-function isRecoverable (error: TSError) {
-  return error.diagnosticCodes.every(code => RECOVERY_CODES.has(code))
-}
-
 /** Safe `hasOwnProperty` */
 function hasOwnProperty (object: any, property: string): boolean {
   return Object.prototype.hasOwnProperty.call(object, property)