- From: Chris Lamb <lamby@debian.org>
- Date: Thu, 28 Jun 2018 19:30:15 +0100
- Subject: [PATCH] Re-use translated content instead of skipping if previously
- translated.
-
- This fixes an issue where an initial `inline` directive would be translated
- correctly, but subsequent inlines of the same would result in the raw
- contents of the `.po` file being inserted into the page instead.
-
- For example, given a `index.mdwn` containing:
-
- \[[!inline pages="inline" raw="yes"]]
- \[[!inline pages="inline" raw="yes"]]
-
- .. and an `index.de.po` of:
-
- msgid "\[[!inline pages=\"inline\" raw=\"yes\"]]\n"
- msgstr "\[[!inline pages=\"inline.de\" raw=\"yes\"]]\n"
-
- .. together with an `inline.mdwn` of:
-
- This is inlined content.
-
- .. and an `inline.de.po` of:
-
- msgid "This is inlined content."
- msgstr "This is German inlined content."
-
- .. would result in the following translation:
-
- This is the inlined content.
- # SOME DESCRIPTIVE TITLE
- # Copyright (C) YEAR Free Software Foundation, Inc.
- # This file is distributed under the same license as the PACKAGE package.
- # FIRST AUTHOR <EMAIL@ADDRESS>, YEAR.
-
- .. instead of, of course:
-
- This is the inlined content.
- This is the inlined content.
- ---
- IkiWiki/Plugin/po.pm | 15 +++++++++------
- 1 file changed, 9 insertions(+), 6 deletions(-)
-
- diff --git a/IkiWiki/Plugin/po.pm b/IkiWiki/Plugin/po.pm
- index 418e8e58a..ecd1f5499 100644
- --- a/IkiWiki/Plugin/po.pm
- +++ b/IkiWiki/Plugin/po.pm
- @@ -303,9 +303,12 @@ sub filter (@) {
- my $page = $params{page};
- my $destpage = $params{destpage};
- my $content = $params{content};
- - if (istranslation($page) && ! alreadyfiltered($page, $destpage)) {
- - $content = po_to_markup($page, $content);
- - setalreadyfiltered($page, $destpage);
- + if (istranslation($page)) {
- + if (!defined(alreadyfiltered($page, $destpage))) {
- + $content = po_to_markup($page, $content);
- + setalreadyfiltered($page, $destpage, $content);
- + }
- + $content = alreadyfiltered($page, $destpage);
- }
- return $content;
- }
- @@ -747,15 +750,15 @@ sub myisselflink ($$) {
- my $page=shift;
- my $destpage=shift;
-
- - return exists $filtered{$page}{$destpage}
- - && $filtered{$page}{$destpage} eq 1;
- + return $filtered{$page}{$destpage};
- }
-
- sub setalreadyfiltered($$) {
- my $page=shift;
- my $destpage=shift;
- + my $content=shift;
-
- - $filtered{$page}{$destpage}=1;
- + $filtered{$page}{$destpage}=$content;
- }
-
- sub unsetalreadyfiltered($$) {
- --
- 2.18.0
-
+There is an issue where an initial "inline" directive would be
+translated correctly but subsequent inlines of the same page would
+result in the raw contents of the ".po" file (ie. starting with the raw
+copyright headers!) being inserted into the page instead.
+
+For example, given a "index.mdwn" containing:
+
+ [[!inline pages="inline" raw="yes"]]
+ [[!inline pages="inline" raw="yes"]]
+
+… and an "index.de.po" of:
+
+ msgid "[[!inline pages=\"inline\" raw=\"yes\"]]\n"
+ msgstr "[[!inline pages=\"inline.de\" raw=\"yes\"]]\n"
+
+… together with an "inline.mdwn" of:
+
+ This is inlined content.
+
+… and an "inline.de.po" of:
+
+ msgid "This is inlined content."
+ msgstr "This is German inlined content."
+
+§
+
+This would result in the following translation:
+
+ This is the inlined content.
+ # SOME DESCRIPTIVE TITLE
+ # Copyright (C) YEAR Free Software Foundation, Inc.
+ # This file is distributed under the same license as the PACKAGE package.
+ # FIRST AUTHOR <EMAIL@ADDRESS>, YEAR.
+
+… instead of (of course)
+
+ This is the inlined content.
+ This is the inlined content.
+
+[[Initially proposed patch from Chris Lamb|20180628-patch.txt]]
+
[[!tag patch]]
> Thank you Chris! I've reviewed the patch (with my "original author of the po plugin" hat on) and it looks good to me. I'm not 100% sure about `alreadyfiltered` being the best name for something that's not a predicated anymore but it's good enough. Then I wore my end-user hat and confirmed that with Chris' patch applied, the reproducer we had for this bug at Tails works fine. So IMO we're good to go and I recommend to apply this patch. Thanks in advance! -- [[intrigeri]]
-
> Any update on getting this merged? — [[lamby]], Fri, 24 Aug 2018 12:36:37 +0200
> Indeed, would love to see this merged! What might be the next steps here? — [[lamby]], Thu, 18 Oct 2018 17:57:37 -0400
-> I've filed this in Debian GNU/Linux at https://bugs.debian.org/911356 — [[lamby]], Thu, 18 Oct 2018 20:18:58 -0400
+> I've filed this in Debian GNU/Linux at <https://bugs.debian.org/911356> — [[lamby]], Thu, 18 Oct 2018 20:18:58 -0400
>> As I said on the Debian bug, I think we badly need test coverage for
>> this sort of thing, otherwise it *will* regress. The po plugin is
>> bugs) without anyone realising.
>>
>> For now I've added a failing test-case for this particular bug.
->> I'll try to review this soon and understand the po plugin, the patch,
->> why the bug exists and why the patch fixes it. --[[smcv]]
+>> --[[smcv]]
+
+---
+
+Review from [[smcv]]:
+
+The patch attached to the Debian bug and the patch pasted here (which
+I've moved to an attachment) appear to be different, but I'm not going to
+do a line-by-line review of the patches and their differences for now
+because I'm not sure their approach is fully correct.
+
+As we know, the two hardest things in computer science are naming, cache
+invalidation and off-by-one errors. Unfortunately this patch has issues
+with naming and cache invalidation. It's effectively turning the
+`alreadyfiltered` mechanism into a cache of memoized results of calling
+`po_to_markup()` on pages' content, keyed by the page name and the
+`destpage`, which is either the page name again or the name of a page
+into which the `page` is to be inlined (even though the result of
+`po_to_markup()` doesn't actually vary with the `destpage`).
+
+This naturally raises the usual concerns about having a cache:
+
+* How large does it grow?
+* Do we invalidate it every time we need to?
+* Do we even need it?
+
+The cache size is mainly a concern for large wikis being rebuilt. If you
+have a wiki with 1000 translated pages in 3 languages each, each of which
+is inlined into an average of one other page, then by the time you finish
+a rebuild you'll be holding 6000 translated pages in memory. If we change
+the `alreadyfiltered` mechanism to be keyed by the page name and not the
+(page, destpage) pair, that drops to 3000, but that's still
+O(pages \* languages) which seems like a lot. As a general design
+principle, ikiwiki tries not to hold full content in RAM for more than
+the currently-processed page.
+
+We invalidate the `alreadyfiltered` for a (page, page) pair in an
+editcontent hook, and we never invalidate (page, destpage) pairs for
+page != destpage at all. Are we sure there is no other circumstance in
+which the content of a page can change?
+
+One of the things I tried doing for a simple solution was to remove the
+cache altogether, because I wasn't sure why we had this `alreadyfiltered`
+mechanism in the first place. This passes tests, which suggests that
+either the `alreadyfiltered` mechanism is unnecessary, or our regression
+test coverage for `po` is insufficient.
+
+Looking back at the history of the `po` plugin, it seems that the
+`alreadyfiltered` mechanism was introduced (under a different name,
+with less abstraction) by [[intrigeri]] in commit 1e874b3f:
+
+```
+po plugin[filter]: avoid converting more than once per destfile
+
+Only the first filter function call on a given {page,destpage} must convert it
+from the PO file, subsequent calls must leave the passed $content unmodified.
+
+Else, preprocessing loops are the rule.
+```
+
+I don't understand this. Under what circumstances would we pass content
+through the filter hooks, and then pass it back through the same filter
+hooks? Can we not do that, instead? If at all possible we should at
+least have test coverage for the situation where this happened (but I
+can't add this without knowing what it was).
+
+I feel as though it should be an invariant that the output of a filter
+hook is never passed back through filter hooks: otherwise every filter
+hook would have to be able to be able to detect and skip processing
+its own output, which is not necessarily even possible. For instance,
+suppose you had a plugin with a filter that turned tab-separated text
+files into `<table>` markup: every HTML file that doesn't contain tabs
+is trivially a TSV file with one column, so you can't know whether a
+blob of text is TSV or HTML.
+
+I wondered whether the loops referenced in 1e874b3f might have been
+fixed in 192ce7a2:
+
+ remove unnecessary and troublesome filter calls
+
+ This better defines what the filter hook is passed, to only be the raw,
+ complete text of a page. Not some snippet, or data read in from an
+ unrelated template.
+
+ Several plugins that filtered text that originates from an (already
+ filtered) page were modified not to do that. Note that this was not
+ done very consistently before; other plugins that receive text from a
+ page called preprocess on it w/o first calling filter.
+
+ The template plugin gets text from elsewhere, and was also changed not to
+ filter it. That leads to one known regression -- the embed plugin cannot
+ be used to embed stuff in templates now. But that plugin is deprecated
+ anyway.
+
+ Later we may want to increase the coverage of what is filtered. Perhaps
+ a good goal would be to allow writing a filter plugin that filters
+ out unwanted words, from any input. We're not there yet; not only
+ does the template plugin load unfiltered text from its templates now,
+ but so can the table plugin, and other plugins that use templates (like
+ inline!). I think we can cross that bridge when we come to it. If I wanted
+ such a censoring plugin, I'd probably make it use a sanitize hook instead,
+ for the better coverage.
+
+ For now I am concentrating on the needs of the two non-deprecated users
+ of filter. This should fix bugs/po_vs_templates, and it probably fixes
+ an obscure bug around txt's use of filter for robots.txt.
+
+but I'm not sure that any of the redundant filtering removed in that
+commit was actually relevant to `po` users?
+
+[[intrigeri]], can you shed any light on this?
+
+Naming is the easy part of this review: the `alreadyfiltered` family of
+functions are not named like cache getter/setter functions. This could
+be resolved by renaming.
--- /dev/null
+From: Chris Lamb <lamby@debian.org>
+Date: Thu, 28 Jun 2018 19:30:15 +0100
+Subject: [PATCH] Re-use translated content instead of skipping if previously
+ translated.
+
+This fixes an issue where an initial `inline` directive would be translated
+correctly, but subsequent inlines of the same would result in the raw
+contents of the `.po` file being inserted into the page instead.
+
+For example, given a `index.mdwn` containing:
+
+ \[[!inline pages="inline" raw="yes"]]
+ \[[!inline pages="inline" raw="yes"]]
+
+.. and an `index.de.po` of:
+
+ msgid "\[[!inline pages=\"inline\" raw=\"yes\"]]\n"
+ msgstr "\[[!inline pages=\"inline.de\" raw=\"yes\"]]\n"
+
+.. together with an `inline.mdwn` of:
+
+ This is inlined content.
+
+.. and an `inline.de.po` of:
+
+ msgid "This is inlined content."
+ msgstr "This is German inlined content."
+
+.. would result in the following translation:
+
+ This is the inlined content.
+ # SOME DESCRIPTIVE TITLE
+ # Copyright (C) YEAR Free Software Foundation, Inc.
+ # This file is distributed under the same license as the PACKAGE package.
+ # FIRST AUTHOR <EMAIL@ADDRESS>, YEAR.
+
+.. instead of, of course:
+
+ This is the inlined content.
+ This is the inlined content.
+---
+ IkiWiki/Plugin/po.pm | 15 +++++++++------
+ 1 file changed, 9 insertions(+), 6 deletions(-)
+
+diff --git a/IkiWiki/Plugin/po.pm b/IkiWiki/Plugin/po.pm
+index 418e8e58a..ecd1f5499 100644
+--- a/IkiWiki/Plugin/po.pm
++++ b/IkiWiki/Plugin/po.pm
+@@ -303,9 +303,12 @@ sub filter (@) {
+ my $page = $params{page};
+ my $destpage = $params{destpage};
+ my $content = $params{content};
+- if (istranslation($page) && ! alreadyfiltered($page, $destpage)) {
+- $content = po_to_markup($page, $content);
+- setalreadyfiltered($page, $destpage);
++ if (istranslation($page)) {
++ if (!defined(alreadyfiltered($page, $destpage))) {
++ $content = po_to_markup($page, $content);
++ setalreadyfiltered($page, $destpage, $content);
++ }
++ $content = alreadyfiltered($page, $destpage);
+ }
+ return $content;
+ }
+@@ -747,15 +750,15 @@ sub myisselflink ($$) {
+ my $page=shift;
+ my $destpage=shift;
+
+- return exists $filtered{$page}{$destpage}
+- && $filtered{$page}{$destpage} eq 1;
++ return $filtered{$page}{$destpage};
+ }
+
+ sub setalreadyfiltered($$) {
+ my $page=shift;
+ my $destpage=shift;
++ my $content=shift;
+
+- $filtered{$page}{$destpage}=1;
++ $filtered{$page}{$destpage}=$content;
+ }
+
+ sub unsetalreadyfiltered($$) {
+--
+2.18.0