Reordering is breaking statements with side-effects.

[mbostock]

Here’s linear.js (abridged):

export function Linear() {};
Linear.prototype.lineStart = function() {};
Linear.prototype.lineEnd = function() {};
Linear.prototype.point = function(x, y) {};

export function LinearClosed() {};
LinearClosed.prototype = Object.create(Linear.prototype);
LinearClosed.prototype.lineEnd = function() {};

The resulting rolled-up file:

function Linear() {}
Linear.prototype.lineStart = function() {};
Linear.prototype.lineEnd = function() {};
Linear.prototype.point = function(x, y) {};

function LinearClosed() {}
LinearClosed.prototype.lineEnd = function() {};
LinearClosed.prototype = Object.create(Linear.prototype);

Note that the last two lines have been reversed, so the assignment to LinearClosed.prototype.lineEnd gets overwritten. This code is in d3-shape. I can work on creating an isolated test case if you need it.

[Rich-Harris]

Thanks. No need for a more isolated test, I reckon this is small enough to work with - will look into it as soon as I get a chance. Not immediately sure what's causing it but am sure it's fixable (he said confidently...)

[Rich-Harris]

@mbostock Turns out I'm struggling to reproduce this - all the d3-shape tests are passing for me, and the statement ordering looks to be correct. Has anything changed since this issue was opened?

[mbostock]

Yeah, there’s a workaround I’ve been using.

I’ll try to pare down a standalone test case.

[mbostock]

Here ya go:

https://gist.github.com/mbostock/bc1ffc78c3f933eff312

Note that if you reverse the order of statements in index.js, the test passes!

[Rich-Harris]

Ah, I see what's going on here. The (new Foo) line causes the Foo definition to be included, which means also including Foo.prototype.test = ... and (because rollup can't know that Object.create doesn't modify Foo.prototype) Bar.prototype = Object.create(Foo.prototype). So the second line, which causes the Bar declaration to be included, doesn't include the Bar.prototype = statement because it's already included.

Not immediately sure what a general solution looks like (the last time I tried to naively sort statements according to their original order, it ended badly), but I'll try a few things. Suggestions welcome!

[Rich-Harris]

Fixed in 0.9.0 - have confirmed all the d3-shape tests now pass without the workaround