Redundant whitespace

A bare XPath expression should read cleanly. Whitespace that the processor ignores still costs the reader: a doubled space, a space hugging a parenthesis, or a stray space at the start or end of the expression all add noise without adding meaning. This check flags whitespace that can be removed without changing what the expression selects.

A whitespace run is redundant when it is longer than a single space, or when it sits at the very start or end of the expression. Whitespace inside a string literal or a comment is left untouched — those spaces are part of the value the author wrote on purpose. The check runs only over expressions that already parse, so a malformed expression is reported once by the validator and never nagged about its spacing.

A run holding a line ending is not redundant either. An expression written across several lines carries the indentation of each line it wraps onto, and that indentation is how a long expression stays readable rather than an accident to collapse:

<xsl:if test="$document/section[@type = 'appendix']
              and $document/section[@type = 'index']">
  <xsl:value-of select="."/>
</xsl:if>

Joining that onto one line would preserve what it selects and lose the reason anyone could read it. Only the doubled spaces standing within a single line are flagged.

Incorrect (a doubled space and a trailing space):

<xsl:if test="foo(  a) = 'hello' ">
  <xsl:value-of select="."/>
</xsl:if>

Correct:

<xsl:if test="foo(a) = 'hello'">
  <xsl:value-of select="."/>
</xsl:if>