gecko/js/examples/jorendb.js

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