repl: add friendly tips about how to exit repl

Imitate python repl, when the user enters 'exit' or 'quit',
no longer prompt 'Reference Error', but
prompts 'To exit, press ^D or type .exit'.
If the user defines variables named 'exit' or 'quit' ,
only the value of the variables are output
PR-URL: #20617Fixes: #19021
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>

Author: monkingxue

lib/repl.js

@@ -215,9 +215,15 @@ function REPLServer(prompt,
 
 functiondefaultEval(code,context,file,cb){
 varerr,result,script,wrappedErr;
+varisExitCommand=false;
 varwrappedCmd=false;
 varawaitPromise=false;
 varinput=code;
+vartrimmedCommand=code.trim();
+
+if(trimmedCommand==='exit'||trimmedCommand==='quit'){
+isExitCommand=true;
+}
 
 if(/^\s*\{/.test(code)&&/\}\s*$/.test(code)){
 // It's confusing for `{ a : 1 }` to be interpreted as a block
@@ -313,10 +319,16 @@ function REPLServer(prompt,
 breakOnSigint: self.breakEvalOnSigint
 };
 
+constlocalContext=self.useGlobal ? global : self.context;
+if(isExitCommand&&!localContext.hasOwnProperty(trimmedCommand)){
+self.outputStream.write('(To exit, press ^D or type .exit)\n');
+returnself.displayPrompt();
+}
+
 if(self.useGlobal){
 result=script.runInThisContext(scriptOptions);
 }else{
-result=script.runInContext(context,scriptOptions);
+result=script.runInContext(localContext,scriptOptions);
 }
 }finally{
 if(self.breakEvalOnSigint){
@@ -332,12 +344,10 @@ function REPLServer(prompt,
 }
 }catch(e){
 err=e;
-
 if(err&&err.code==='ERR_SCRIPT_EXECUTION_INTERRUPTED'){
-// The stack trace for this case is not very useful anyway.
+// The stack trace for this case is not very useful anyway.
 Object.defineProperty(err,'stack',{value: ''});
 }
-
 if(process.domain){
 debug('not recoverable, send to domain');
 process.domain.emit('error',err);

test/parallel/test-repl.js

@@ -132,6 +132,29 @@ const strictModeTests = [
 }
 ];
 
+constfriendlyExitTests=[
+{
+send: 'exit',
+expect: '(To exit, press ^D or type .exit)'
+},
+{
+send: 'quit',
+expect: '(To exit, press ^D or type .exit)'
+},
+{
+send: 'quit = 1',
+expect: '1'
+},
+{
+send: 'quit',
+expect: '1'
+},
+{
+send: 'exit',
+expect: '(To exit, press ^D or type .exit)'
+},
+];
+
 consterrorTests=[
 // Uncaught error throws and prints out
 {
@@ -742,6 +765,7 @@ const tcpTests = [
 const[socket,replServer]=awaitstartUnixRepl();
 
 awaitrunReplTests(socket,prompt_unix,unixTests);
+awaitrunReplTests(socket,prompt_unix,friendlyExitTests);
 awaitrunReplTests(socket,prompt_unix,errorTests);
 replServer.replMode=repl.REPL_MODE_STRICT;
 awaitrunReplTests(socket,prompt_unix,strictModeTests);