Combination of JavaScript is flawed
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Key: TAP5-769
URL: https://issues.apache.org/jira/browse/TAP5-769
Project: Tapestry 5
Issue Type: Bug
Components: tapestry-core
Affects Versions: 5.1.0.5
Reporter: Andy Blower
Tapestry's JavaScript combination functionality is flawed. Each page &
component specifies which JS files it needs, which means that JS can be split
into functional units (good for development & maintenance) and only the JS
that's actually needed for that page is added for the client to download. The
consequence of this is that pages can have lots of JS files to download, all of
which have to be downloaded before the page is loaded/rendered now that the
script link tags are enforced to be back in the head section. Our results page
has 34 JS files for instance.
Yahoo's YSlow tool recommends that these files are combined and minified, and
Tapestry includes functionality to do the first (minifying is on the TODO list
I believe) as a response to this recommendation which is good. Unfortunately
the implementation based on only having the JS files required for a page means
that the combined JS can easily be unique for each page of a site. This means
that the client browser has to download & cache lots of large JS multiple times
(prototype, scriptaculous, tapestry etc) which I think is probably worse than
requesting them separately, but only downloading stuff once and using that for
all pages.
To solve this issue, Tapestry script combination should combine all of the
scripts needed for the site, and not just the unique set for each page. That
way only a single JS file needs to be downloaded and cached by the client
browser. I'm aware that this may not be that easy given the existing way only
scripts needed for the page are put on it, so an alternative solution that may
be easier to implement would be to combine scripts into two files for each
page. The first file would contain all of the commonly Tapestry provided JS
such as prototype.js, scriptaculous.js, effects.js, tapestry.js, etc in one
file that's the same for every page, and have the rest in a second file that is
unique for the page but that is not likely to include very large JS files, just
many little ones.
A second flaw that the combination has is that if an external JS file is
requested, script combination is aborted rather than just excluding the
external file.
One other thing that surprised me about Tapestry's script combination is the
length of the generated filename, for example it's 919 characters long for a
page on our site:
H4sIAAAAAAAAALVW7ZLSMBTFGX0Rx$002fFrZgk7gvjDH0plBWdRho6ujjpOmt7ChTTpJmlZfBYfwVfzHUwKRRiFXUrlV0hPzs39OKf9$002bat253utdrtmf3drjwnVGowmmilMDGUpl6kmrfppvVFvkURJI80igfpU1$002br7sVu7Dv9wPx6iCJjJkfcKpKEJaKMWa1Cx4VD3C1TAKZsFqMI1bL3jcCfXsp3EoDUdQx78cwFn3C4SaiaEsfDps0bUeNJstprtoE2YjF0tLlN7nNAksWCpgGNApjSjy$002fzIUCZpcoEilPNzFLNqyfuCo4APlGNIDUrhyL2C3B76J20iBQj7PF4o0EAVmxAfx6Iv3mWgOM2r2i1BMlQQgQLBQLtMHQ2tKlGO44nJEOZkqv$002f8cSFGR4XYyGQj$002bxelS3gmVewYnu9lyNYNI6kGJWhc9FAqd$002fpNifieAmpgqGSEHDZy$002bXZYfXIT2N2HpfQxcW0o1i7K$002b6q60BeR7KRBwHNzebTfLJgURkmea6q9U99FlBivUNiapka6gBwMHC$002fGFanHpab20i8tubdB3rlpJwsNObfw02BqTfActSk9jTQDP186hi9VdWcEOuVGnyE3VulhJ5$002bw1wfm2MMwBNFDM6BqBsqfo1le8zgpb0ypJ$002bUMlz7eu$002bnlMtQp5SFoq2MyoCg8O1z2yciZzUG$002busXUvbRrT$002fI0Fgcpe4vEnuc00WgHzLeDsTL6B9e8ea2hgCrlwtYEbv3YNQOvrM2MqBjD1jC4OJ$002f$002by5jlbfxaFfVgMVppxJuA$002fTqQV47$002bYwmJ$002fc10gWby1jpihGz9Nq7MGLsi9O33yZL2NyNGzuevCQAA.js
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