Re: search-default-mode char-fold-to-regexp and Greek Extended block characters

[Juri Linkov <juri@linkov.net>]

>     >> Done as f9337bc36d
>     Juri> Thanks!  Could you please look why tests fail to validate matching of
>     Juri> n-level decomposition.  The character with 3 level decomposition in
>     Juri> char-fold--test-without-customization is currently commented out as
>     Juri> FIXME.  After uncommenting this test fails, and I don't understand why.
>
> That test ends up doing
>
> (string-match "\\`\\(?:ι[̀́̄̆̈̓̔͂]\\|[ΐίιϊἰ-ἷὶίιῐ-ΐῖῗ𝛊𝜄𝜾𝝸𝞲]\\)\\'" "Ϊ́")
>
> because it does (upcase "ΐ") => Ϊ́
>
> That character is GREEK SMALL LETTER IOTA WITH DIALYTIKA AND OXIA, and
> as far as I can tell there is no CAPITAL variant of that letter, so
> upcase canʼt return it, which means it returns GREEK CAPITAL LETTER
> IOTA plus the diacriticals, which is obviously not going to
> match.

This is an interesting case like (upcase "ß") => "SS" that required
adding (?ß "ss") to pass the tests.  So I guess we need to add (?ι "ΐ")
for the tests to pass:

diff --git a/test/lisp/char-fold-tests.el b/test/lisp/char-fold-tests.el
index e519435ef0..3819f3919d 100644
--- a/test/lisp/char-fold-tests.el
+++ b/test/lisp/char-fold-tests.el
@@ -166,6 +165,7 @@ char-fold--test-with-customization
   (let* ((char-fold-include
           '(
             (?ß "ss") ;; de
+            (?ι "ΐ")  ;; el
             (?o "ø")  ;; da no nb nn
             (?l "ł")  ;; pl
             ))
@@ -184,9 +184,7 @@ char-fold--test-with-customization
           '(
             ("e" "ℯ" "ḗ" "ë" "ë")
             ("е" "ё" "ё")
-            ("ι" "ί" "ί"
-             ;; FIXME: "ΐ"
-             )
+            ("ι" "ί" "ί" "ΐ")
             ("ß" "ss")
             ("o" "ø")
             ("l" "ł")


But this is only for char-fold--test-with-customization.  OTOH, for
char-fold--test-without-customization we need also to change the default
value in char-fold.el like:

diff --git a/lisp/char-fold.el b/lisp/char-fold.el
index f379229e6c..c4add03bd9 100644
--- a/lisp/char-fold.el
+++ b/lisp/char-fold.el
@@ -27,7 +27,8 @@
   (defconst char-fold--default-include
     '((?\" "＂" "“" "”" "”" "„" "⹂" "〞" "‟" "‟" "❞" "❝" "❠" "“" "„" "〝" "〟" "🙷" "🙶" "🙸" "«" "»")
       (?' "❟" "❛" "❜" "‘" "’" "‚" "‛" "‚" "󠀢" "❮" "❯" "‹" "›")
-      (?` "❛" "‘" "‛" "󠀢" "❮" "‹")))
+      (?` "❛" "‘" "‛" "󠀢" "❮" "‹")
+      (?ι "ΐ")))
   (defconst char-fold--default-exclude nil)
   (defconst char-fold--default-symmetric nil)
   (defconst char-fold--previous (list char-fold--default-include

diff --git a/test/lisp/char-fold-tests.el b/test/lisp/char-fold-tests.el
index e519435ef0..3819f3919d 100644
--- a/test/lisp/char-fold-tests.el
+++ b/test/lisp/char-fold-tests.el
@@ -154,8 +154,7 @@ char-fold--test-without-customization
             ("ι"
              "ί" ;; 1 level decomposition
              "ί" ;; 2 level decomposition
-             ;; FIXME:
-             ;; "ΐ" ;; 3 level decomposition
+             "ΐ" ;; 3 level decomposition
              )
             )))
     (dolist (strings matches)