tsc 4.7 - 4.8.4 hangs indefinitely

[Lokomojo]

Bug Report

🔎 Search Terms

tsc hangs indefinitely

🕗 Version & Regression Information

• This changed between versions 4.6.4 and 4.7.2 (still occurs in 4.8.4)

⏯ Playground Link

It happens in a large project, I can't figure out exactly what is triggering the behaviour, can someone advise on how I can see what file it's getting stuck on? Or otherwise how to get some verbosity out of the compiler?

💻 Code

(See above)

🙁 Actual behavior

tsc hangs and never completes

🙂 Expected behavior

tsc 4.6.4 and below completes compilation after ~ 3 seconds.

[RyanCavanaugh]

I need to put this in the wiki...

The best way to start tracking these down is to attach a debugger and see which line of code is causing TS to hang:

• Run node --inspect-brk path/to/tsc.js --yourCmdLine where path/to/tsc.js is an actual path to tsc.js and --yourCmdLine is what you would normally pass tsc
• Attach with your debugger of choice (about:inspect in Chromium-based browsers works well)
• Run
• Wait for a bit, then pause the debugger to see what's going on. Depending on the stack frame, you'll have a few clues available to work from:
• If you have a node, run ts.getTextOfNode(node) in the console to see its text. You can use ts.getTextOfNode(node.parent), ts.getTextOfNode(node.parent.parent), and so on, to get more context if needed
• If something with a name that suggest it's a symbol is in scope, symbol.valueDeclaration and/or symbol.declarations will be a node or array of nodes (respectively) that can be inspected the same way
• If it's crashing on a type, you can use ts.typeToString(type) to get more information about it. Types also usually have a symbol property which will in turn lead to you the node that declared them

Hope that helps!

[Lokomojo]

Thanks, i'll get on that.

(As an aside, could we consider adding a -vvv switch to get tsc to actually output what it's doing?)

[RyanCavanaugh]

TS spends a huge amount of its time running the same small handful of functions many times, so even a simple if (verbose) check in any one of those would have a measurable performance impact.

[C0t300]

I'm having the same exact issue on a new VM on azure. Running tsc on a (not so large) project hangs and stays 'running' for hours.

[Lokomojo]

Okay, I don't know how useful this is going to be..

This code causes the infinite hang:

if (item.extraParams !== undefined)
{
    if (item.extraParams.lightImageData !== undefined)
    {
        if (item.extraParams.lightImageData && item.extraParams.lightImageData.texture && !item.extraParams.lightImageData.texture.equals(UUID.zero()))
        {
            const uuidStr = item.extraParams.lightImageData.texture.toString();
            if (this.textures[uuidStr] === undefined)
            {
                if (!UUID.zero().equals(uuidStr))
                {
                    this.textures[uuidStr] = new TextureAsset(this.bot, item.extraParams.lightImageData.texture);
                }
            }
        }
    }
    if (item.extraParams.sculptData && item.extraParams.sculptData.texture && !item.extraParams.sculptData.texture.equals(UUID.zero()))
    {
        const uuidStr = item.extraParams.sculptData.texture.toString();
        if (this.textures[uuidStr] === undefined)
        {
            if (!UUID.zero().equals(uuidStr))
            {
                this.textures[uuidStr] = new TextureAsset(this.bot, item.extraParams.sculptData.texture);
            }
        }
    }
}

If i remove either of the above blocks, e.g

if (item.extraParams !== undefined)
{
    if (item.extraParams.lightImageData !== undefined)
    {
        if (item.extraParams.lightImageData && item.extraParams.lightImageData.texture && !item.extraParams.lightImageData.texture.equals(UUID.zero()))
        {
            const uuidStr = item.extraParams.lightImageData.texture.toString();
            if (this.textures[uuidStr] === undefined)
            {
                if (!UUID.zero().equals(uuidStr))
                {
                    this.textures[uuidStr] = new TextureAsset(this.bot, item.extraParams.lightImageData.texture);
                }
            }
        }
    }
}

Then it does complete the compilation, albeit very slowly

└─$ time tsc

real    41.11s
user    45.03s
sys     0.11s
cpu     109%

Without either block:

└─$ time tsc

real    4.05s
user    7.76s
sys     0.14s
cpu     194%

If i re-arrange the code a bit, it is fine:

if (item.extraParams !== undefined)
{
    if (item.extraParams.lightImageData)
    {
        const texture = item.extraParams.lightImageData.texture;
        if (texture && !texture.equals(UUID.zero()))
        {
            const uuidStr = texture.toString();
            if (this.textures[uuidStr] === undefined)
            {
                if (!UUID.zero().equals(uuidStr))
                {
                    this.textures[uuidStr] = new TextureAsset(this.bot, texture);
                }
            }
        }
    }
    if (item.extraParams.sculptData)
    {
        const texture = item.extraParams.sculptData.texture;
        if (texture && !texture.equals(UUID.zero()))
        {
            const uuidStr = texture.toString();
            if (this.textures[uuidStr] === undefined)
            {
                if (!UUID.zero().equals(uuidStr))
                {
                    this.textures[uuidStr] = new TextureAsset(this.bot, texture);
                }
            }
        }
    }
}

└─$ time tsc

real    5.52s
user    9.62s
sys     0.13s
cpu     176%

I ran node --prof /usr/lib64/node_modules/typescript/lib/tsc.js (left it running for five minutes, with the first code block I pasted above) and got the results as attached.

profile.zip

(The report is incomplete because it ran out of memory even with a 64gb heap >.<)

[Lokomojo]

I ran the profiler again with a much shorter (1 minute) run, and it completed the analysis

processed3.zip

[bdrazen]

For me the issue seems to be an infinite loop occurring within inferFromMatchingTypes:

function inferFromMatchingTypes(sources, targets, matches) {
    var matchedSources;
    var matchedTargets;
    for (var _i = 0, targets_1 = targets; _i < targets_1.length; _i++) {
        var t = targets_1[_i];
        for (var _a = 0, sources_1 = sources; _a < sources_1.length; _a++) {
            var s = sources_1[_a];
            if (matches(s, t)) {
                inferFromTypes(s, t);
                matchedSources = ts.appendIfUnique(matchedSources, s);
                matchedTargets = ts.appendIfUnique(matchedTargets, t);
            }
        }
    }
    return [
        matchedSources ? ts.filter(sources, function (t) { return !ts.contains(matchedSources, t); }) : sources,
        matchedTargets ? ts.filter(targets, function (t) { return !ts.contains(matchedTargets, t); }) : targets,
    ];
}

No idea what's going on but seems to be resolved in v5.

[RyanCavanaugh]

We need a standalone repro we can test locally in order to investigate this. Please open a new issue if you have one. Thanks!