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Redmine Ruby master - Bug #13671 (Assigned): Regexp with lookbehind and case-insensitivity raises RegexpE...https://redmine.ruby-lang.org/issues/136712017-06-22T23:28:58Zdschweisguth (Dave Schweisguth)dave@schweisguth.org
<p>Here is a test program:</p>
<pre><code class="ruby syntaxhl" data-language="ruby"><span class="k">def</span> <span class="nf">test</span><span class="p">(</span><span class="n">description</span><span class="p">)</span>
<span class="k">begin</span>
<span class="k">yield</span>
<span class="nb">puts</span> <span class="s2">"</span><span class="si">#{</span><span class="n">description</span><span class="si">}</span><span class="s2"> is OK"</span>
<span class="k">rescue</span> <span class="no">RegexpError</span>
<span class="nb">puts</span> <span class="s2">"</span><span class="si">#{</span><span class="n">description</span><span class="si">}</span><span class="s2"> raises RegexpError"</span>
<span class="k">end</span>
<span class="k">end</span>
<span class="nb">test</span><span class="p">(</span><span class="s2">"ass, case-insensitive, special"</span><span class="p">)</span> <span class="p">{</span> <span class="sr">/(?<!ass)/i</span> <span class="o">=~</span> <span class="s1">'✨'</span> <span class="p">}</span>
<span class="nb">test</span><span class="p">(</span><span class="s2">"bss, case-insensitive, special"</span><span class="p">)</span> <span class="p">{</span> <span class="sr">/(?<!bss)/i</span> <span class="o">=~</span> <span class="s1">'✨'</span> <span class="p">}</span>
<span class="nb">test</span><span class="p">(</span><span class="s2">"as, case-insensitive, special"</span><span class="p">)</span> <span class="p">{</span> <span class="sr">/(?<!as)/i</span> <span class="o">=~</span> <span class="s1">'✨'</span> <span class="p">}</span>
<span class="nb">test</span><span class="p">(</span><span class="s2">"ss, case-insensitive, special"</span><span class="p">)</span> <span class="p">{</span> <span class="sr">/(?<!ss)/i</span> <span class="o">=~</span> <span class="s1">'✨'</span> <span class="p">}</span>
<span class="nb">test</span><span class="p">(</span><span class="s2">"ass, case-sensitive, special"</span><span class="p">)</span> <span class="p">{</span> <span class="sr">/(?<!ass)/</span> <span class="o">=~</span> <span class="s1">'✨'</span> <span class="p">}</span>
<span class="nb">test</span><span class="p">(</span><span class="s2">"ass, case-insensitive, regular"</span><span class="p">)</span> <span class="p">{</span> <span class="sr">/(?<!ass)/i</span> <span class="o">=~</span> <span class="s1">'x'</span> <span class="p">}</span>
</code></pre>
<p>Running the test program with Ruby 2.4.1 (macOS) gives</p>
<pre><code>ass, case-insensitive, special raises RegexpError
bss, case-insensitive, special raises RegexpError
as, case-insensitive, special is OK
ss, case-insensitive, special is OK
ass, case-sensitive, special is OK
ass, case-insensitive, regular is OK
</code></pre>
<p>The RegexpError is "invalid pattern in look-behind: /(?<!ass)/i (RegexpError)"</p>
<p>Side note: in the real code in which I found this error I was able to work around the error by using (?i) after the lookbehind instead of //i.</p>
<p>Running the test program with Ruby 2.3.4 does not report any RegexpErrors.</p>
<p>I think this is a regression, although I might be wrong and it might be saving me from an incorrect result with certain strings.</p>