conf.py: tweak SearchEnglish to be hyphen-friendly

This modifies the default indexer split() and js splitQuery()
methods to support searching for words with hyphens.

While this might not be an ideal, rock solid, and fully future-proof
solution, it allows at least to search for strings inlcuding hyphens,
such as 'bitbake-layers', 'send-error-report', or 'oe-core'.

Below is a bit more detailed explanation of the two modifications done:

1) The default split regex in the sphinx-doc SearchLanguage base class
   is:

   | _word_re = re.compile(r'\w+')

   which we simply extend to include hyphens '-'.

   This will result in a searchindex.js that contains words with hyphens,
   too.

2) The 'searchtool.js' code notes for its splitQuery() implementation:

   | /**
   |  * Default splitQuery function. Can be overridden in ``sphinx.search`` with a
   |  * custom function per language.
   |  *
   |  * The regular expression works by splitting the string on consecutive characters
   |  * that are not Unicode letters, numbers, underscores, or emoji characters.
   |  * This is the same as ``\W+`` in Python, preserving the surrogate pair area.
   |  */
   | if (typeof splitQuery === "undefined") {
   |   var splitQuery = (query) => query
   |       .split(/[^\p{Letter}\p{Number}_\p{Emoji_Presentation}]+/gu)
   |       .filter(term => term)  // remove remaining empty strings
   | }

   The hook for this is documented in the sphinx-docs 'SearchLanguage'
   base class.

   |    .. attribute:: js_splitter_code
   |
   |       Return splitter function of JavaScript version.  The function should be
   |       named as ``splitQuery``.  And it should take a string and return list of
   |       strings.
   |
   |       .. versionadded:: 3.0

   We use this to define a simplified splitQuery() function with a split
   argument that splits on empty spaces only.

We extend SearchEnglish (which extends SearchLanguage) here to retain
the stemmer code and stopwords for English.

[YOCTO #14534]

(From yocto-docs rev: 72e70a6af6eb3d4ca41f9e64069d8d3f61b420a3)

Signed-off-by: Enrico Jörns <ejo@pengutronix.de>
Signed-off-by: Antonin Godard <antonin.godard@bootlin.com>
(cherry picked from commit d4a98ee19e0cbd6be96923dc72faee143a6b294b)
Signed-off-by: Antonin Godard <antonin.godard@bootlin.com>
Signed-off-by: Steve Sakoman <steve@sakoman.com>

documentation/conf.py

@@ -13,6 +13,7 @@
 # documentation root, use os.path.abspath to make it absolute, like shown here.
 #
 import os
+import re
 import sys
 import datetime
 try:
@@ -165,6 +166,24 @@ latex_elements = {
     'preamble': '\\setcounter{tocdepth}{2}',
 }
 
+
+from sphinx.search import SearchEnglish
+from sphinx.search import languages
+class DashFriendlySearchEnglish(SearchEnglish):
+
+    # Accept words that can include hyphens
+    _word_re = re.compile(r'[\w\-]+')
+
+    js_splitter_code = """
+function splitQuery(query) {
+    return query
+        .split(/[^\p{Letter}\p{Number}_\p{Emoji_Presentation}-]+/gu)
+        .filter(term => term.length > 0);
+}
+"""
+
+languages['en'] = DashFriendlySearchEnglish
+
 # Make the EPUB builder prefer PNG to SVG because of issues rendering Inkscape SVG
 from sphinx.builders.epub3 import Epub3Builder
 Epub3Builder.supported_image_types = ['image/png', 'image/gif', 'image/jpeg']