michael@0: /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
michael@0:  * vim: set ts=8 sw=4 et tw=78:
michael@0:  *
michael@0:  * jorendb - A toy command-line debugger for shell-js programs.
michael@0:  *
michael@0:  * This Source Code Form is subject to the terms of the Mozilla Public
michael@0:  * License, v. 2.0. If a copy of the MPL was not distributed with this
michael@0:  * file, You can obtain one at http://mozilla.org/MPL/2.0/.
michael@0:  */
michael@0: 
michael@0: /*
michael@0:  * jorendb is a simple command-line debugger for shell-js programs. It is
michael@0:  * intended as a demo of the Debugger object (as there are no shell js programs
michael@0:  * to speak of).
michael@0:  *
michael@0:  * To run it: $JS -d path/to/this/file/jorendb.js
michael@0:  * To run some JS code under it, try:
michael@0:  *    (jorendb) print load("my-script-to-debug.js")
michael@0:  * Execution will stop at debugger statements and you'll get a jorendb prompt.
michael@0:  */
michael@0: 
michael@0: // Debugger state.
michael@0: var focusedFrame = null;
michael@0: var topFrame = null;
michael@0: var debuggeeValues = {};
michael@0: var nextDebuggeeValueIndex = 1;
michael@0: var lastExc = null;
michael@0: 
michael@0: // Cleanup functions to run when we next re-enter the repl.
michael@0: var replCleanups = [];
michael@0: 
michael@0: // Convert a debuggee value v to a string.
michael@0: function dvToString(v) {
michael@0:     return (typeof v !== 'object' || v === null) ? uneval(v) : "[object " + v.class + "]";
michael@0: }
michael@0: 
michael@0: function showDebuggeeValue(dv) {
michael@0:     var dvrepr = dvToString(dv);
michael@0:     var i = nextDebuggeeValueIndex++;
michael@0:     debuggeeValues["$" + i] = dv;
michael@0:     print("$" + i + " = " + dvrepr);
michael@0: }
michael@0: 
michael@0: Object.defineProperty(Debugger.Frame.prototype, "num", {
michael@0:     configurable: true,
michael@0:     enumerable: false,
michael@0:     get: function () {
michael@0:             var i = 0;
michael@0:             for (var f = topFrame; f && f !== this; f = f.older)
michael@0:                 i++;
michael@0:             return f === null ? undefined : i;
michael@0:         }
michael@0:     });
michael@0: 
michael@0: Debugger.Frame.prototype.frameDescription = function frameDescription() {
michael@0:     if (this.type == "call")
michael@0:         return ((this.callee.name || '<anonymous>') +
michael@0:                 "(" + this.arguments.map(dvToString).join(", ") + ")");
michael@0:     else
michael@0:         return this.type + " code";
michael@0: }
michael@0: 
michael@0: Debugger.Frame.prototype.positionDescription = function positionDescription() {
michael@0:     if (this.script) {
michael@0:         var line = this.script.getOffsetLine(this.offset);
michael@0:         if (this.script.url)
michael@0:             return this.script.url + ":" + line;
michael@0:         return "line " + line;
michael@0:     }
michael@0:     return null;
michael@0: }
michael@0: 
michael@0: Debugger.Frame.prototype.fullDescription = function fullDescription() {
michael@0:     var fr = this.frameDescription();
michael@0:     var pos = this.positionDescription();
michael@0:     if (pos)
michael@0:         return fr + ", " + pos;
michael@0:     return fr;
michael@0: }
michael@0: 
michael@0: Object.defineProperty(Debugger.Frame.prototype, "line", {
michael@0:         configurable: true,
michael@0:         enumerable: false,
michael@0:         get: function() {
michael@0:             if (this.script)
michael@0:                 return this.script.getOffsetLine(this.offset);
michael@0:             else
michael@0:                 return null;
michael@0:         }
michael@0:     });
michael@0: 
michael@0: function callDescription(f) {
michael@0:     return ((f.callee.name || '<anonymous>') +
michael@0:             "(" + f.arguments.map(dvToString).join(", ") + ")");
michael@0: }
michael@0: 
michael@0: function showFrame(f, n) {
michael@0:     if (f === undefined || f === null) {
michael@0:         f = focusedFrame;
michael@0:         if (f === null) {
michael@0:             print("No stack.");
michael@0:             return;
michael@0:         }
michael@0:     }
michael@0:     if (n === undefined) {
michael@0:         n = f.num;
michael@0:         if (n === undefined)
michael@0:             throw new Error("Internal error: frame not on stack");
michael@0:     }
michael@0: 
michael@0:     print('#' + n + " " + f.fullDescription());
michael@0: }
michael@0: 
michael@0: function saveExcursion(fn) {
michael@0:     var tf = topFrame, ff = focusedFrame;
michael@0:     try {
michael@0:         return fn();
michael@0:     } finally {
michael@0:         topFrame = tf;
michael@0:         focusedFrame = ff;
michael@0:     }
michael@0: }
michael@0: 
michael@0: // Evaluate an expression in the Debugger global
michael@0: function evalCommand(expr) {
michael@0:     eval(expr);
michael@0: }
michael@0: 
michael@0: function quitCommand() {
michael@0:     dbg.enabled = false;
michael@0:     quit(0);
michael@0: }
michael@0: 
michael@0: function backtraceCommand() {
michael@0:     if (topFrame === null)
michael@0:         print("No stack.");
michael@0:     for (var i = 0, f = topFrame; f; i++, f = f.older)
michael@0:         showFrame(f, i);
michael@0: }
michael@0: 
michael@0: function printCommand(rest) {
michael@0:     // This is the real deal.
michael@0:     var cv = saveExcursion(
michael@0:         () => focusedFrame == null
michael@0:               ? debuggeeGlobalWrapper.evalInGlobalWithBindings(rest, debuggeeValues)
michael@0:               : focusedFrame.evalWithBindings(rest, debuggeeValues));
michael@0:     if (cv === null) {
michael@0:         if (!dbg.enabled)
michael@0:             return [cv];
michael@0:         print("Debuggee died.");
michael@0:     } else if ('return' in cv) {
michael@0:         if (!dbg.enabled)
michael@0:             return [undefined];
michael@0:         showDebuggeeValue(cv.return);
michael@0:     } else {
michael@0:         if (!dbg.enabled)
michael@0:             return [cv];
michael@0:         print("Exception caught. (To rethrow it, type 'throw'.)");
michael@0:         lastExc = cv.throw;
michael@0:         showDebuggeeValue(lastExc);
michael@0:     }
michael@0: }
michael@0: 
michael@0: function detachCommand() {
michael@0:     dbg.enabled = false;
michael@0:     return [undefined];
michael@0: }
michael@0: 
michael@0: function continueCommand() {
michael@0:     if (focusedFrame === null) {
michael@0:         print("No stack.");
michael@0:         return;
michael@0:     }
michael@0:     return [undefined];
michael@0: }
michael@0: 
michael@0: function throwCommand(rest) {
michael@0:     var v;
michael@0:     if (focusedFrame !== topFrame) {
michael@0:         print("To throw, you must select the newest frame (use 'frame 0').");
michael@0:         return;
michael@0:     } else if (focusedFrame === null) {
michael@0:         print("No stack.");
michael@0:         return;
michael@0:     } else if (rest === '') {
michael@0:         return [{throw: lastExc}];
michael@0:     } else {
michael@0:         var cv = saveExcursion(function () { return focusedFrame.eval(rest); });
michael@0:         if (cv === null) {
michael@0:             if (!dbg.enabled)
michael@0:                 return [cv];
michael@0:             print("Debuggee died while determining what to throw. Stopped.");
michael@0:         } else if ('return' in cv) {
michael@0:             return [{throw: cv.return}];
michael@0:         } else {
michael@0:             if (!dbg.enabled)
michael@0:                 return [cv];
michael@0:             print("Exception determining what to throw. Stopped.");
michael@0:             showDebuggeeValue(cv.throw);
michael@0:         }
michael@0:         return;
michael@0:     }
michael@0: }
michael@0: 
michael@0: function frameCommand(rest) {
michael@0:     var n, f;
michael@0:     if (rest.match(/[0-9]+/)) {
michael@0:         n = +rest;
michael@0:         f = topFrame;
michael@0:         if (f === null) {
michael@0:             print("No stack.");
michael@0:             return;
michael@0:         }
michael@0:         for (var i = 0; i < n && f; i++) {
michael@0:             if (!f.older) {
michael@0:                 print("There is no frame " + rest + ".");
michael@0:                 return;
michael@0:             }
michael@0:             f.older.younger = f;
michael@0:             f = f.older;
michael@0:         }
michael@0:         focusedFrame = f;
michael@0:         showFrame(f, n);
michael@0:     } else if (rest !== '') {
michael@0:         if (topFrame === null)
michael@0:             print("No stack.");
michael@0:         else
michael@0:             showFrame();
michael@0:     } else {
michael@0:         print("do what now?");
michael@0:     }
michael@0: }
michael@0: 
michael@0: function upCommand() {
michael@0:     if (focusedFrame === null)
michael@0:         print("No stack.");
michael@0:     else if (focusedFrame.older === null)
michael@0:         print("Initial frame selected; you cannot go up.");
michael@0:     else {
michael@0:         focusedFrame.older.younger = focusedFrame;
michael@0:         focusedFrame = focusedFrame.older;
michael@0:         showFrame();
michael@0:     }
michael@0: }
michael@0: 
michael@0: function downCommand() {
michael@0:     if (focusedFrame === null)
michael@0:         print("No stack.");
michael@0:     else if (!focusedFrame.younger)
michael@0:         print("Youngest frame selected; you cannot go down.");
michael@0:     else {
michael@0:         focusedFrame = focusedFrame.younger;
michael@0:         showFrame();
michael@0:     }
michael@0: }
michael@0: 
michael@0: function forcereturnCommand(rest) {
michael@0:     var v;
michael@0:     var f = focusedFrame;
michael@0:     if (f !== topFrame) {
michael@0:         print("To forcereturn, you must select the newest frame (use 'frame 0').");
michael@0:     } else if (f === null) {
michael@0:         print("Nothing on the stack.");
michael@0:     } else if (rest === '') {
michael@0:         return [{return: undefined}];
michael@0:     } else {
michael@0:         var cv = saveExcursion(function () { return f.eval(rest); });
michael@0:         if (cv === null) {
michael@0:             if (!dbg.enabled)
michael@0:                 return [cv];
michael@0:             print("Debuggee died while determining what to forcereturn. Stopped.");
michael@0:         } else if ('return' in cv) {
michael@0:             return [{return: cv.return}];
michael@0:         } else {
michael@0:             if (!dbg.enabled)
michael@0:                 return [cv];
michael@0:             print("Error determining what to forcereturn. Stopped.");
michael@0:             showDebuggeeValue(cv.throw);
michael@0:         }
michael@0:     }
michael@0: }
michael@0: 
michael@0: function printPop(f, c) {
michael@0:     var fdesc = f.fullDescription();
michael@0:     if (c.return) {
michael@0:         print("frame returning (still selected): " + fdesc);
michael@0:         showDebuggeeValue(c.return);
michael@0:     } else if (c.throw) {
michael@0:         print("frame threw exception: " + fdesc);
michael@0:         showDebuggeeValue(c.throw);
michael@0:         print("(To rethrow it, type 'throw'.)");
michael@0:         lastExc = c.throw;
michael@0:     } else {
michael@0:         print("frame was terminated: " + fdesc);
michael@0:     }
michael@0: }
michael@0: 
michael@0: // Set |prop| on |obj| to |value|, but then restore its current value
michael@0: // when we next enter the repl.
michael@0: function setUntilRepl(obj, prop, value) {
michael@0:     var saved = obj[prop];
michael@0:     obj[prop] = value;
michael@0:     replCleanups.push(function () { obj[prop] = saved; });
michael@0: }
michael@0: 
michael@0: function doStepOrNext(kind) {
michael@0:     var startFrame = topFrame;
michael@0:     var startLine = startFrame.line;
michael@0:     print("stepping in:   " + startFrame.fullDescription());
michael@0:     print("starting line: " + uneval(startLine));
michael@0: 
michael@0:     function stepPopped(completion) {
michael@0:         // Note that we're popping this frame; we need to watch for
michael@0:         // subsequent step events on its caller.
michael@0:         this.reportedPop = true;
michael@0:         printPop(this, completion);
michael@0:         topFrame = focusedFrame = this;
michael@0:         return repl();
michael@0:     }
michael@0: 
michael@0:     function stepEntered(newFrame) {
michael@0:         print("entered frame: " + newFrame.fullDescription());
michael@0:         topFrame = focusedFrame = newFrame;
michael@0:         return repl();
michael@0:     }
michael@0: 
michael@0:     function stepStepped() {
michael@0:         print("stepStepped: " + this.fullDescription());
michael@0:         // If we've changed frame or line, then report that.
michael@0:         if (this !== startFrame || this.line != startLine) {
michael@0:             topFrame = focusedFrame = this;
michael@0:             if (focusedFrame != startFrame)
michael@0:                 print(focusedFrame.fullDescription());
michael@0:             return repl();
michael@0:         }
michael@0: 
michael@0:         // Otherwise, let execution continue.
michael@0:         return undefined;
michael@0:     }
michael@0: 
michael@0:     if (kind.step)
michael@0:         setUntilRepl(dbg, 'onEnterFrame', stepEntered);
michael@0: 
michael@0:     // If we're stepping after an onPop, watch for steps and pops in the
michael@0:     // next-older frame; this one is done.
michael@0:     var stepFrame = startFrame.reportedPop ? startFrame.older : startFrame;
michael@0:     if (!stepFrame || !stepFrame.script)
michael@0:         stepFrame = null;
michael@0:     if (stepFrame) {
michael@0:         setUntilRepl(stepFrame, 'onStep', stepStepped);
michael@0:         setUntilRepl(stepFrame, 'onPop',  stepPopped);
michael@0:     }
michael@0: 
michael@0:     // Let the program continue!
michael@0:     return [undefined];
michael@0: }
michael@0: 
michael@0: function stepCommand() { return doStepOrNext({step:true}); }
michael@0: function nextCommand() { return doStepOrNext({next:true}); }
michael@0: 
michael@0: // Build the table of commands.
michael@0: var commands = {};
michael@0: var commandArray = [
michael@0:     backtraceCommand, "bt", "where",
michael@0:     continueCommand, "c",
michael@0:     detachCommand,
michael@0:     downCommand, "d",
michael@0:     forcereturnCommand,
michael@0:     frameCommand, "f",
michael@0:     nextCommand, "n",
michael@0:     printCommand, "p",
michael@0:     quitCommand, "q",
michael@0:     stepCommand, "s",
michael@0:     throwCommand, "t",
michael@0:     upCommand, "u",
michael@0:     helpCommand, "h",
michael@0:     evalCommand, "!",
michael@0:     ];
michael@0: var last = null;
michael@0: for (var i = 0; i < commandArray.length; i++) {
michael@0:     var cmd = commandArray[i];
michael@0:     if (typeof cmd === "string")
michael@0:         commands[cmd] = last;
michael@0:     else
michael@0:         last = commands[cmd.name.replace(/Command$/, '')] = cmd;
michael@0: }
michael@0: 
michael@0: function helpCommand(rest) {
michael@0:     print("Available commands:");
michael@0:     var printcmd = function(group) {
michael@0:         print("  " + group.join(", "));
michael@0:     }
michael@0: 
michael@0:     var group = [];
michael@0:     for (var cmd of commandArray) {
michael@0:         if (typeof cmd === "string") {
michael@0:             group.push(cmd);
michael@0:         } else {
michael@0:             if (group.length) printcmd(group);
michael@0:             group = [ cmd.name.replace(/Command$/, '') ];
michael@0:         }
michael@0:     }
michael@0:     printcmd(group);
michael@0: }
michael@0: 
michael@0: // Break cmd into two parts: its first word and everything else. If it begins
michael@0: // with punctuation, treat that as a separate word.
michael@0: function breakcmd(cmd) {
michael@0:     cmd = cmd.trimLeft();
michael@0:     if ("!@#$%^&*_+=/?.,<>:;'\"".indexOf(cmd.substr(0, 1)) != -1)
michael@0:         return [cmd.substr(0, 1), cmd.substr(1).trimLeft()];
michael@0:     var m = /\s/.exec(cmd);
michael@0:     if (m === null)
michael@0:         return [cmd, ''];
michael@0:     return [cmd.slice(0, m.index), cmd.slice(m.index).trimLeft()];
michael@0: }
michael@0: 
michael@0: function runcmd(cmd) {
michael@0:     var pieces = breakcmd(cmd);
michael@0:     if (pieces[0] === "")
michael@0:         return undefined;
michael@0: 
michael@0:     var first = pieces[0], rest = pieces[1];
michael@0:     if (!commands.hasOwnProperty(first)) {
michael@0:         print("unrecognized command '" + first + "'");
michael@0:         return undefined;
michael@0:     }
michael@0: 
michael@0:     var cmd = commands[first];
michael@0:     if (cmd.length === 0 && rest !== '') {
michael@0:         print("this command cannot take an argument");
michael@0:         return undefined;
michael@0:     }
michael@0: 
michael@0:     return cmd(rest);
michael@0: }
michael@0: 
michael@0: function repl() {
michael@0:     while (replCleanups.length > 0)
michael@0:         replCleanups.pop()();
michael@0: 
michael@0:     var cmd;
michael@0:     for (;;) {
michael@0:         putstr("\n" + prompt);
michael@0:         cmd = readline();
michael@0:         if (cmd === null)
michael@0:             return null;
michael@0: 
michael@0:         try {
michael@0:             var result = runcmd(cmd);
michael@0:             if (result === undefined)
michael@0:                 ; // do nothing
michael@0:             else if (Array.isArray(result))
michael@0:                 return result[0];
michael@0:             else
michael@0:                 throw new Error("Internal error: result of runcmd wasn't array or undefined");
michael@0:         } catch (exc) {
michael@0:             print("*** Internal error: exception in the debugger code.");
michael@0:             print("    " + exc);
michael@0:             print(exc.stack);
michael@0:         }
michael@0:     }
michael@0: }
michael@0: 
michael@0: var dbg = new Debugger();
michael@0: dbg.onDebuggerStatement = function (frame) {
michael@0:     return saveExcursion(function () {
michael@0:             topFrame = focusedFrame = frame;
michael@0:             print("'debugger' statement hit.");
michael@0:             showFrame();
michael@0:             return repl();
michael@0:         });
michael@0: };
michael@0: dbg.onThrow = function (frame, exc) {
michael@0:     return saveExcursion(function () {
michael@0:             topFrame = focusedFrame = frame;
michael@0:             print("Unwinding due to exception. (Type 'c' to continue unwinding.)");
michael@0:             showFrame();
michael@0:             print("Exception value is:");
michael@0:             showDebuggeeValue(exc);
michael@0:             return repl();
michael@0:         });
michael@0: };
michael@0: 
michael@0: // The depth of jorendb nesting.
michael@0: var jorendbDepth;
michael@0: if (typeof jorendbDepth == 'undefined') jorendbDepth = 0;
michael@0: 
michael@0: var debuggeeGlobal = newGlobal("new-compartment");
michael@0: debuggeeGlobal.jorendbDepth = jorendbDepth + 1;
michael@0: var debuggeeGlobalWrapper = dbg.addDebuggee(debuggeeGlobal);
michael@0: 
michael@0: print("jorendb version -0.0");
michael@0: prompt = '(' + Array(jorendbDepth+1).join('meta-') + 'jorendb) ';
michael@0: 
michael@0: var args = arguments;
michael@0: while(args.length > 0) {
michael@0:     var arg = args.shift();
michael@0:     if (arg == '-f') {
michael@0:         arg = args.shift();
michael@0:         debuggeeGlobal.evaluate(read(arg), { fileName: arg, lineNumber: 1 });
michael@0:     } else if (arg == '-e') {
michael@0:         arg = args.shift();
michael@0:         debuggeeGlobal.eval(arg);
michael@0:     } else {
michael@0:         throw("jorendb does not implement command-line argument '" + arg + "'");
michael@0:     }
michael@0: }
michael@0: 
michael@0: repl();