Module talk:DecodeEncode

Bug report: bad decoding of U+03B5 ε (epsilon)

Tracked in Phabricator
Task T328840

About U+03B5 ε GREEK SMALL LETTER EPSILON (ε ε)

• Issue: after resolving HTML entity ε by mw.text.decode(), the plain character is not found by mw.ustring.gsub(). No issue with alternative HTML entity ε. ε good, ε bad.

Report limitations: Original report and bug reproduction is at enwiki Module talk:DecodeEncode, from where en:module:DecodeEncode and en:module:String are used live. At phabricator pseudocode may be used and some "results" may be hardcoded. In-text the escape & is used, not in-function. Lua patterns not used ("no %").

• To reproduce:

1. Create research string:

Xε1Xε2X (shows live and unedited as: Xε1Xε2X)

2. Render the string by decode() (as inner function)

3. then on rendered result use gsub() to replace plain character ε → E: (as outer function)

mw.ustring.gsub( s=(mw.text.decode( s=Xε1Xε2X, decodeNamedEntities=true ) ), pattern=ε, repl=E ) [is pseudo-code, see note. 21:10, 7 February 2023 (UTC)]

4. Result3 (s&r pattern use ε from Xε1X):

XE1XE2X

5. Result4 (s&r pattern use ε from Xε2X):

XE1XE2X

• Expected: XE1XE2X (only one character ε exists)

• Note 21:10, 7 February 2023 (UTC): This step 3 is in pseudo-code. To reproduce, use Lua modules module:String and Module:DecodeEncode:

{{#invoke:String|replace|source={{#invoke:DecodeEncode|decode|s=Xε1Xε2X}}|pattern=ε|replace=E|plain=true}}

→ XE1XE2X

-DePiep (talk) 21:10, 7 February 2023 (UTC)

Workaround A, ad hoc

Workaround A, ad hoc: add innermost function to first replace in the research string ε → ε:

A1: {{#invoke:String|replace|source={{#invoke:DecodeEncode|decode|s={{#invoke:String|replace|source=Xε1Xε2X|pattern=ε|replace=ε|plain=true}}}}|pattern=ε|replace=E|plain=true}} →

XE1XE2X

Workaround B, in module (THIN SPACE example)

Workaround B: early in :en:module:DecodeEncode, replace ε → ε

About THIN SPACE: it looks like character U+2009 THIN SPACE (   ) has a samilar issue.   good,   bad.

Currently in code:

function p._decode( s, subset_only )
	local ret = nil;
    s = mw.ustring.gsub( s, ' ', ' ' ) -- Workaround for bug:   gets properly decoded in decode, but   doesn't.
	ret = mw.text.decode( s, not subset_only )
	return ret
end

In en:module:DecodeEncode/sandbox, I have coded a similar handling of EPSILON:

module:DecodeEncode, module:DecodeEncode/sandbox diff

function p._decode( s, subset_only )
	local ret = nil;
	-- U+2009 THIN SPACE: workaround for bug: HTML entity   is decoded incorrect. Entity   gets decoded properly
	s = mw.ustring.gsub( s, ' ', ' ' )
	-- U+03B5 ε GREEK SMALL LETTER EPSILON: workaround for bug (phab:...): HTML entity ε is decoded incorrect for gsub(). Entity ε gets decoded properly
	s = mw.ustring.gsub( s, 'ε', 'ε' )
	ret = mw.text.decode( s, not subset_only )
	return ret
end

• /sandbox tests:

B. {{#invoke:String|replace|source={{#invoke:DecodeEncode/sandbox|decode|s=Xε1Xε2X}}|pattern=ε|replace=E|plain=true}}

B1. ResultB1 (s&r pattern use ε from Xε1X): XE1XE2X

B2. ResultB2 (s&r pattern use ε from Xε2X): XE1XE2X

I propose to edit the module along this way.

Workaround C (mw, Lua)

Changes in mw, Lua: I have not idea.

• I propose to consider module editing along § Workaround B. -DePiep (talk) 12:26, 4 February 2023 (UTC)