Friday, December 16, 2016

Need some help with debugging an issue in GWT SDM compiler

Hi!

I have this strange problem in SDM, where a method in the generated output JS gets defined under a name, but gets referenced under another name.

I'll try to show it through actual compiled JS code vs original code.

function getBoundingClientRect_3_g$(this$static_0_g$, withinOffsetParent_0_g$){
  $clinit_ElementOverlayMixin_0_g$();
  var deltaX_0_g$, deltaY_0_g$, offsetParent_0_g$, parentBCR_0_g$;
  offsetParent_0_g$ = $getOffsetParent_0_g$(this$static_0_g$);
  if (is_4_g$(offsetParent_0_g$)) {
    parentBCR_0_g$ = $getBoundingClientRect_2_g$(as_58_g$(offsetParent_0_g$), true);
    deltaY_0_g$ = $getScrollTop_0_g$(offsetParent_0_g$) - parentBCR_0_g$.getTop_15_g$();
    deltaX_0_g$ = $getScrollLeft_0_g$(offsetParent_0_g$) - parentBCR_0_g$.getLeft_16_g$();
  }
   else {
    deltaY_0_g$ = getScrollTop_4_g$();
    deltaX_0_g$ = getScrollLeft_6_g$();
  }
  return withinOffsetParent_0_g$?$getBoundingClientRect_1_g$(this$static_0_g$).translated_1_g$(deltaX_0_g$, deltaY_0_g$):$getBoundingClientRect_1_g$(this$static_0_g$);
}
getBoundingClientRect_3_g$.displayName = 'ElementOverlayMixin.$getBoundingClientRect';


This is the original Java source of the method:

public final ClientRect getBoundingClientRect(boolean withinOffsetParent) {
float deltaY;
float deltaX;
Element offsetParent = getOffsetParent();
if (Element.is(offsetParent)) {
ClientRect parentBCR = ElementOverlayMixin.as(offsetParent).getBoundingClientRect(true);
deltaY = offsetParent.getScrollTop() - parentBCR.getTop();
deltaX = offsetParent.getScrollLeft() - parentBCR.getLeft();
} else {
deltaY = Window.getScrollTop();
deltaX = Window.getScrollLeft();
}
return withinOffsetParent ? getBoundingClientRect().translated(deltaX, deltaY) : getBoundingClientRect();
}

I've highlighted the important parts with bold+red/green. Note that it's a recursive method invoking itself on another object. In the generated output, the name of the function in the function declaration and the name used while referring to the same function is different.

After a "touch" on the source code file, the compiler now generates the correct JS output:

function $getBoundingClientRect_2_g$(this$static_0_g$, withinOffsetParent_0_g$){
  $clinit_ElementOverlayMixin_0_g$();
  var deltaX_0_g$, deltaY_0_g$, offsetParent_0_g$, parentBCR_0_g$;
  offsetParent_0_g$ = $getOffsetParent_0_g$(this$static_0_g$);
  if (is_4_g$(offsetParent_0_g$)) {
    parentBCR_0_g$ = $getBoundingClientRect_2_g$(as_58_g$(offsetParent_0_g$), true);
    deltaY_0_g$ = $getScrollTop_0_g$(offsetParent_0_g$) - parentBCR_0_g$.getTop_15_g$();
    deltaX_0_g$ = $getScrollLeft_0_g$(offsetParent_0_g$) - parentBCR_0_g$.getLeft_16_g$();
  }
   else {
    deltaY_0_g$ = getScrollTop_4_g$();
    deltaX_0_g$ = getScrollLeft_6_g$();
  }
  return withinOffsetParent_0_g$?$getBoundingClientRect_1_g$(this$static_0_g$).translated_1_g$(deltaX_0_g$, deltaY_0_g$):$getBoundingClientRect_1_g$(this$static_0_g$);
}

$getBoundingClientRect_2_g$.displayName = 'ElementOverlayMixin.$getBoundingClientRect';

I'm using incremental mode, but I think it happened on the first compilation too with all previous compilation caches cleared.

Do you guys have any tips on where to look in the compiler code where the method name handling / mangling happens?

Many thanks!

Nandi.

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