debugger: add a command to set which lines to check for context

PR-URL: #46812
Reviewed-By: Kohei Ueno <kohei.ueno119@gmail.com>

Author: Dailyscat

lib/internal/debugger/inspect_repl.js

@@ -46,7 +46,7 @@ const {
 
 const{ERR_DEBUGGER_ERROR}=require('internal/errors').codes;
 
-const{ validateString }=require('internal/validators');
+const{ validateString, validateNumber}=require('internal/validators');
 
 constFS=require('fs');
 constPath=require('path');
@@ -81,7 +81,7 @@ out, o Step out, leaving the current function
 backtrace, bt Print the current backtrace
 list Print the source around the current line where execution
  is currently paused
-
+setContextLineNumber Set which lines to check for context
 setBreakpoint, sb Set a breakpoint
 clearBreakpoint, cb Clear a breakpoint
 breakpoints List all known breakpoints
@@ -381,6 +381,7 @@ function createRepl(inspector) {
 letcurrentBacktrace;
 letselectedFrame;
 letexitDebugRepl;
+letcontextLineNumber=2;
 
 functionresetOnStart(){
 knownScripts={};
@@ -685,6 +686,15 @@ function createRepl(inspector) {
 });
 }
 
+functionsetContextLineNumber(delta=2){
+if(!selectedFrame){
+thrownewERR_DEBUGGER_ERROR('Requires execution to be paused');
+}
+validateNumber(delta,'delta',1);
+contextLineNumber=delta;
+print(`The contextLine has been changed to ${delta}.`);
+}
+
 functionhandleBreakpointResolved({ breakpointId, location }){
 constscript=knownScripts[location.scriptId];
 constscriptUrl=script&&script.url;
@@ -897,7 +907,7 @@ function createRepl(inspector) {
 
 inspector.suspendReplWhile(()=>
 PromisePrototypeThen(
-SafePromiseAllReturnArrayLike([formatWatchers(true),selectedFrame.list(2)]),
+SafePromiseAllReturnArrayLike([formatWatchers(true),selectedFrame.list(contextLineNumber)]),
 ({0: watcherList,1: context})=>{
 constbreakContext=watcherList ?
 `${watcherList}\n${inspect(context)}` :
@@ -1159,6 +1169,7 @@ function createRepl(inspector) {
 },
 
  list,
+ setContextLineNumber,
 });
 aliasProperties(context,SHORTCUTS);
 }

test/fixtures/debugger/twenty-lines.js

@@ -0,0 +1,20 @@
+letx=0;
+x=1;
+x=2;
+x=3;
+x=4;
+x=5;
+x=6;
+x=7;
+x=8;
+x=9;
+x=10;
+x=11;
+x=12;
+x=13;
+x=14;
+x=15;
+x=16;
+x=17;
+x=18;
+module.exports=x;

test/sequential/test-debugger-set-context-line-number.mjs

@@ -0,0 +1,50 @@
+import{skipIfInspectorDisabled}from'../common/index.mjs';
+skipIfInspectorDisabled();
+
+import{path}from'../common/fixtures.mjs';
+importstartCLIfrom'../common/debugger.js';
+
+importassertfrom'assert';
+
+constscript=path('debugger','twenty-lines.js');
+constcli=startCLI([script]);
+
+functiononFatal(error){
+cli.quit();
+throwerror;
+}
+
+functiongetLastLine(output){
+constsplittedByLine=output.split(';');
+returnsplittedByLine[splittedByLine.length-2];
+}
+
+// Stepping through breakpoints.
+try{
+awaitcli.waitForInitialBreak();
+awaitcli.waitForPrompt();
+
+awaitcli.command('setContextLineNumber("1")');
+assert.ok(cli.output.includes('argument must be of type number. Received type string'));
+
+awaitcli.command('setContextLineNumber(0)');
+assert.ok(cli.output.includes('It must be >= 1. Received 0'));
+
+// Make sure the initial value is 2.
+awaitcli.stepCommand('n');
+assert.ok(getLastLine(cli.output).includes('4 x = 3'));
+
+awaitcli.command('setContextLineNumber(5)');
+awaitcli.stepCommand('n');
+assert.ok(getLastLine(cli.output).includes('8 x = 7'));
+
+awaitcli.command('setContextLineNumber(3)');
+awaitcli.stepCommand('n');
+assert.ok(getLastLine(cli.output).includes('7 x = 6'));
+awaitcli.command('list(3)');
+assert.ok(getLastLine(cli.output).includes('7 x = 6'));
+
+awaitcli.quit();
+}catch(error){
+onFatal(error);
+}