Module: Canon::Xml::WhitespacePolicy

Defined in:
lib/canon/xml/whitespace_policy.rb

Overview

Parse-time whitespace policy: whether a character-data node survives conversion. One home for the keep/strip rules so the DOM/SAX/HTML differences are visible here instead of implied by copy-paste across conversion sites.

Document-level character data (outside the root element) can only be whitespace per the XML grammar, and the XPath data model — which canon's tree and C14N follow — has no root text children at all. Every policy therefore drops whitespace-only document-level text; engines that report it (libxml2 does not, libleptris 1.9.38+ does) stay byte-compatible through here.

Constant Summary collapse

STRIP_ONLY =

Zero-allocation forms of the content.strip.empty? / content.gsub(...).empty? checks these policies used to run per text node. STRIP_ONLY is exactly String#strip's set (ASCII whitespace plus null); SAX drops space/tab/CR/LF runs.

/\A[\0\t\n\v\f\r ]*\z/
SAX_DROPPED = 
/\A[ \t\r\n]*\z/
HTML_WHITESPACE_SENSITIVE_TAGS =

HTML conversion rule: whitespace-only text is dropped except in whitespace-sensitive elements (pre/code/textarea/script/style), between inline siblings (semantically significant), and when it carries NBSP (U+00A0 — never insignificant; strip is ASCII-only so it is checked explicitly).

%w[pre code textarea script style].freeze
HTML_SENSITIVE_TAG_SET =

Set form for the hot lookup; element names arrive lowercased from the HTML parser, so the downcase fallback only allocates for unusual (non-lowercased) names.

HTML_WHITESPACE_SENSITIVE_TAGS.to_set

Class Method Summary collapse

Class Method Details

.keep_dom_text?(content, preserve_whitespace:, element_parent: true) ⇒ Boolean

DOM conversion rule: whitespace-only text is dropped unless preserving. Non-ASCII whitespace (NBSP, U+3000) survives — String#strip only removes ASCII whitespace.

NOTE: CR-only nodes are dropped on this path; the SAX rule keeps them (character references must survive for C14N).

Returns:

  • (Boolean) 


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# File 'lib/canon/xml/whitespace_policy.rb', line 34

def keep_dom_text?(content, preserve_whitespace:,
element_parent: true)
  # The XPath data model has no root text children — drop
  # whitespace-only document-level text even when preserving
  # (engines that report it stay byte-compatible with libxml2).
  return false if !element_parent && content.match?(STRIP_ONLY)

  return true if preserve_whitespace

  !content.match?(STRIP_ONLY)
end

.keep_html_text?(content, parent_name:, text_node: nil) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/canon/xml/whitespace_policy.rb', line 70

def keep_html_text?(content, parent_name:, text_node: nil)
  return true unless content.match?(STRIP_ONLY)
  return true if content.include?(" ")

  parent_name = parent_name.to_s
  return true if HTML_SENSITIVE_TAG_SET.include?(parent_name)
  return true if HTML_SENSITIVE_TAG_SET.include?(parent_name.downcase)

  # Computed last: the sibling scan is O(siblings), so it must
  # not run for the content-bearing text nodes that fail the
  # whitespace-only check above.
  return true if text_node &&
    Canon::Comparison::WhitespaceSensitivity.inline_whitespace_significant?(text_node)

  false
end

.keep_sax_text?(content, preserve_whitespace:, element_parent: true) ⇒ Boolean

SAX rule: same shape, plus CR-bearing content is always kept ( must survive parsing for C14N) — only runs of pure ASCII whitespace (space, tab, CR, LF) are dropped when not preserving.

Returns:

  • (Boolean) 


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# File 'lib/canon/xml/whitespace_policy.rb', line 49

def keep_sax_text?(content, preserve_whitespace:,
element_parent: true)
  return false if !element_parent && content.match?(STRIP_ONLY)

  return true if preserve_whitespace
  return true if content.include?("\r")

  !content.match?(SAX_DROPPED)
end