feat(#292): void-attributes-not-higher-than-other

[h1alexbel]

In this PR I've introduced void-attributes-not-higher-than-other lint, that issues defect with critical severity, if void attribute (∅) is located lower than sibling non-void attributes.

closes #292

[h1alexbel]

@maxonfjvipon check this one, please

[maxonfjvipon]

@h1alexbel I just wonder why you don't cut processed objects here, in this place like: //o[@base='∅' and preceding-sibling::o[@base != '∅'].
Instead you split it into two parts which makes you create two xsl:template (I can be wrong here, but it seems to be not a good practice) and add extra xsl:if block.
Does such approach improve something? Speed? Readability? Maintainability?

[h1alexbel]

@maxonfjvipon yes, it looks a bit more complicated than simple for-each. Read this: https://www.onenaught.com/posts/23/xslt-tips-for-cleaner-code-and-better-performance (Avoid xsl:for-each; Use Template Match section in particular). WDYT?

[maxonfjvipon]

@h1alexbel ok, I got it about xs:for-each, but I'm not suggest you to use it. I suggest to move the predicate from xsl:if to template applying section at line 31:

   <xsl:apply-templates select="//o[@base='∅' and preceding-sibling::o[@base != '∅']" mode="low-void"/>
   ...
  <xsl:template match="o" mode="low-void">
    <defect>
      <xsl:attribute name="line">
        <xsl:value-of select="eo:lineno(@line)"/>
      </xsl:attribute>
      <xsl:attribute name="severity">critical</xsl:attribute>
      <xsl:text>Void attribute </xsl:text>
      <xsl:value-of select="eo:escape(@name)"/>
      <xsl:text> must be higher than any other non-void attribute</xsl:text>
    </defect>
  </xsl:template>

It seems more convenient to me because there's no more place where we potentially can put any other predicate. Are there any disadvantages of such appoach?

BTW: you forgot to add mode to you template

[h1alexbel]

@maxonfjvipon looks good to me

[h1alexbel]

@maxonfjvipon updated. Take a look, please

[h1alexbel]

@yegor256 take a look, please

[h1alexbel]

@yegor256 reminder

[h1alexbel]

@yegor256 reminder

[yegor256]

@h1alexbel thanks!