While I was porting apps from Imba 1 to Imba 2 I encountered a bug in Imba 2, but I was too busy to deal with it. Let's take a step back, try to reproduce a bug with minimal case, and then submit it.
The Bug
The bug was that when I'd put debugger statement in the code, depending on where it was, Imba would stack overflow.
Getting to replication
I don't remember which apps had this issue, so I'll try it first with imba2-game-of-life. Fortunately if it works I won't even need to run it, it will be obvious on the terminal.
So I opened client.imba and started adding debugger in various places.
It took zero time to get a crash, in any function where I use it after a block, here's an example:
def countNeighbours(cells, x, y) let count = 0 for cell of cells if !cell.state continue let dx = Math.abs(cell.x - x) let dy = Math.abs(cell.y - y) if Math.max(dx, dy) == 1 count += 1 count def runStep(cells) let nextCells = [] for cell of cells let n = countNeighbours(cells, cell.x, cell.y) let nextState = (n == 3 || (cell.state && n == 2)) nextCells.push({x: cell.x, y: cell.y, state: nextState}) nextCells tag cell prop data def onclick data.state = !data.state emit("pause") def render let visualStartX = 20 * data.x + 1 let visualStartY = 20 * data.y + 1 <self[left:{visualStartX}px top:{visualStartY}px] .alive=(data.state) .dead=(!data.state) @click.onclick> css position: absolute width: 18px height: 18px &.dead background-color: #864 &.alive background-color: #3f3 tag app prop cells prop playing = true def setup let sizex = 30 let sizey = 30 cells = [] for x in [0 ... sizex] for y in [0 ... sizey] cells.push({ x: x, y: y, state: Math.random() < 0.2 }) def step cells = runStep(cells) def mount imba.setInterval(&,100) do if playing step() debugger def play playing = true def pause playing = false def render <self> <header> "Game of Life" <div.board> for cell in cells <cell data=cell @pause.pause> <div.buttons> if playing <button @click.pause> "Pause" else <button @click.step> "Step" <button @click.play> "Play" css header font-size: 64px text-align: center .board position: relative height: 600px width: 600px background-color: #aaa margin: auto .buttons text-align: center button margin: 0.5em imba.mount <app> And error message in the terminal:
ERROR COMPILING IMBA RangeError: Maximum call stack size exceeded at Yp.J.consume (~/imba2-game-of-life/node_modules/imba/compiler.imba.js:79:11138) at Qe.c (~/imba2-game-of-life/node_modules/imba/compiler.imba.js:88:4768) at Qe.c (~/imba2-game-of-life/node_modules/imba/compiler.imba.js:88:4782) at Qe.c (~/imba2-game-of-life/node_modules/imba/compiler.imba.js:88:4782) at Qe.c (~/imba2-game-of-life/node_modules/imba/compiler.imba.js:88:4782) at Qe.c (~/imba2-game-of-life/node_modules/imba/compiler.imba.js:88:4782) at Qe.c (~/imba2-game-of-life/node_modules/imba/compiler.imba.js:88:4782) at Qe.c (~/imba2-game-of-life/node_modules/imba/compiler.imba.js:88:4782) at Qe.c (~/imba2-game-of-life/node_modules/imba/compiler.imba.js:88:4782) at Qe.c (~/imba2-game-of-life/node_modules/imba/compiler.imba.js:88:4782) app/client.imba Removing irrelevant parts
OK, we don't need an app, we just need a clear test case. So time to remove all extra stuff. And step by step, after each one verifying that the crash is still there, I arrived at this:
def foo debugger Even that causes the same crash.
Exploring other ways to trigger the bug
OK, so right now a debugger at the end of the method crashes Imba compiler. But I'm pretty sure I saw this in other contexts too.
Looks like putting debugger at end of a block also does it:
def foo imba.setInterval(&,1000) do debugger I think I saw this happen in some other contexts, but I can't reproduce it right now. So maybe I'm misremembering, and possibly a fix for this would also deal with more complex cases anyway.
Time to submit a bug
Next step is to go to GitHub issues for Imba and do a search for debugger. It doesn't look like it was reported before, so time to submit it.
As usual, I deleted the pre-made template, as I find them more annoying than useful. So here's the bug report.
In retrospect I should have saved the failing code as I was coding, even if I didn't have time to write a bug report.
Coming next
In the next episode I'll give some thoughts about Imba 2.
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