Class: Canon::Comparison::XmlComparator

Inherits:
MarkupComparator show all
Defined in:
lib/canon/comparison/xml_comparator.rb

Overview

XML comparison class Handles comparison of XML nodes with various options

Inherits shared comparison functionality from MarkupComparator.

Constant Summary collapse

DEFAULT_OPTS =

Default comparison options for XML

{
  # Structural filtering options
  ignore_children: false,
  ignore_text_nodes: false,
  ignore_attr_content: [],
  ignore_attrs: [],
  ignore_attrs_by_name: [],
  ignore_nodes: [],

  # Output options
  verbose: false,
  diff_children: false,

  # Match system options
  match_profile: nil,
  match: nil,
  preprocessing: nil,
  global_profile: nil,
  global_options: nil,

  # Diff display options
  diff: nil,
}.freeze

Class Method Summary collapse

Methods inherited from MarkupComparator

add_difference, build_difference_reason, comment_node?, determine_node_dimension, extract_attributes, extract_text_content_from_node, filter_children, node_excluded?, node_text, same_node_type?, serialize_node, text_node?, truncate_text, whitespace_only_difference?

Class Method Details

.comment_vs_non_comment_comparison?(node1, node2) ⇒ Boolean

Check if this is a comment vs non-comment comparison

Parameters:

  • node1 (Object) —

    First node

  • node2 (Object) —

    Second node

Returns:

  • (Boolean) —

    true if exactly one node is a comment



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# File 'lib/canon/comparison/xml_comparator.rb', line 292

def comment_vs_non_comment_comparison?(node1, node2)
  node1_comment = XmlNodeComparison
    .comment_node?(node1, check_children: true)
  node2_comment = XmlNodeComparison
    .comment_node?(node2, check_children: true)

  # XOR: exactly one is a comment
  node1_comment ^ node2_comment
end

.compare_attribute_sets(n1, n2, opts, differences) ⇒ Object

Compare attribute sets Delegates to XmlComparatorHelpers::AttributeComparator



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# File 'lib/canon/comparison/xml_comparator.rb', line 363

def compare_attribute_sets(n1, n2, opts, differences)
  XmlComparatorHelpers::AttributeComparator.compare(n1, n2, opts,
                                                    differences)
end

.compare_children(n1, n2, opts, child_opts, diff_children, differences) ⇒ Object

Compare children of two nodes using semantic matching

Delegates to ChildComparison module which handles both ElementMatcher (semantic matching) and simple positional comparison.



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# File 'lib/canon/comparison/xml_comparator.rb', line 535

def compare_children(n1, n2, opts, child_opts, diff_children,
differences)
  XmlComparatorHelpers::ChildComparison.compare(
    n1, n2, self, opts, child_opts, diff_children, differences
  )
end

.compare_comment_nodes(n1, n2, opts, differences) ⇒ Object

Compare comment nodes



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# File 'lib/canon/comparison/xml_comparator.rb', line 465

def compare_comment_nodes(n1, n2, opts, differences)
  match_opts = opts[:match_opts]
  behavior = match_opts[:comments]

  # Canon::Xml::Node CommentNode uses .value, Nokogiri uses .content
  content1 = node_text(n1)
  content2 = node_text(n2)

  # Check if content differs
  contents_differ = content1 != content2

  # Create DiffNode in verbose mode when content differs
  # This ensures informative diffs are created even for :ignore behavior
  if contents_differ && opts[:verbose]
    add_difference(n1, n2, Comparison::UNEQUAL_COMMENTS,
                   Comparison::UNEQUAL_COMMENTS, :comments, opts,
                   differences)
  end

  # Return based on behavior and whether content matches
  if behavior == :ignore || !contents_differ
    Comparison::EQUIVALENT
  else
    Comparison::UNEQUAL_COMMENTS
  end
end

.compare_document_nodes(n1, n2, opts, child_opts, diff_children, differences) ⇒ Object

Compare document nodes



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# File 'lib/canon/comparison/xml_comparator.rb', line 515

def compare_document_nodes(n1, n2, opts, child_opts, diff_children,
                           differences)
  # Compare root elements
  root1 = n1.root
  root2 = n2.root

  if root1.nil? || root2.nil?
    add_difference(n1, n2, Comparison::MISSING_NODE,
                   Comparison::MISSING_NODE, :text_content, opts, differences)
    return Comparison::MISSING_NODE
  end

  compare_nodes(root1, root2, opts, child_opts, diff_children,
                differences)
end

.compare_element_nodes(n1, n2, opts, child_opts, diff_children, differences) ⇒ Object

Compare two element nodes



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# File 'lib/canon/comparison/xml_comparator.rb', line 305

def compare_element_nodes(n1, n2, opts, child_opts, diff_children,
                          differences)
  # Compare element names
  unless n1.name == n2.name
    add_difference(n1, n2, Comparison::UNEQUAL_ELEMENTS,
                   Comparison::UNEQUAL_ELEMENTS, :element_structure, opts,
                   differences)
    return Comparison::UNEQUAL_ELEMENTS
  end

  # Compare namespace URIs - elements with different namespaces are different elements
  ns1 = Canon::XmlParsing.namespace_uri(n1)
  ns2 = Canon::XmlParsing.namespace_uri(n2)

  unless ns1 == ns2
    # The DiffNode is only ever appended in verbose mode — skip
    # building it entirely otherwise.
    if opts[:verbose]
      differences << Canon::Comparison::DiffNodeBuilder.build(
        node1: n1,
        node2: n2,
        diff1: Comparison::UNEQUAL_ELEMENTS,
        diff2: Comparison::UNEQUAL_ELEMENTS,
        dimension: :namespace_uri,
        verbose: true,
      )
    end
    return Comparison::UNEQUAL_ELEMENTS
  end

  # Track the worst result across namespace, attribute, and children
  # comparisons. Do NOT return early on attribute/namespace mismatches —
  # children must still be compared so structural differences in the
  # subtree are reported. Early returns caused the comparator to skip
  # entire subtrees when a root or intermediate element had different
  # attributes, missing all nested structural changes.
  worst_result = Comparison::EQUIVALENT

  # Compare namespace declarations (xmlns and xmlns:* attributes)
  ns_result = compare_namespace_declarations(n1, n2, opts, differences)
  worst_result = ns_result unless ns_result == Comparison::EQUIVALENT

  # Compare attributes
  attr_result = compare_attribute_sets(n1, n2, opts, differences)
  worst_result = attr_result unless attr_result == Comparison::EQUIVALENT

  # Compare children if not ignored
  unless opts[:ignore_children]
    child_result = compare_children(n1, n2, opts, child_opts,
                                    diff_children, differences)
    worst_result = child_result unless child_result == Comparison::EQUIVALENT
  end

  worst_result
end

.compare_namespace_declarations(n1, n2, opts, differences) ⇒ Object

Compare namespace declarations (xmlns and xmlns:* attributes) Delegates to XmlComparatorHelpers::NamespaceComparator



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# File 'lib/canon/comparison/xml_comparator.rb', line 572

def compare_namespace_declarations(n1, n2, opts, differences)
  XmlComparatorHelpers::NamespaceComparator.compare(n1, n2, opts,
                                                    differences)
end

.compare_nodes(n1, n2, opts, child_opts, diff_children, differences) ⇒ Object

Main comparison dispatcher



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# File 'lib/canon/comparison/xml_comparator.rb', line 216

def compare_nodes(n1, n2, opts, child_opts, diff_children, differences)
  # FAST PATH: Object identity - same object is always equivalent
  return Comparison::EQUIVALENT if n1.equal?(n2)

  # Handle DocumentFragment nodes - compare their children instead
  if Canon::XmlParsing.document_fragment?(n1) &&
      Canon::XmlParsing.document_fragment?(n2)
    children1 = n1.children.to_a
    children2 = n2.children.to_a

    if children1.length != children2.length
      add_difference(n1, n2, Comparison::UNEQUAL_ELEMENTS,
                     Comparison::UNEQUAL_ELEMENTS, :text_content, opts,
                     differences)
      return Comparison::UNEQUAL_ELEMENTS
    elsif children1.empty?
      return Comparison::EQUIVALENT
    else
      # Compare each pair of children
      result = Comparison::EQUIVALENT
      children1.zip(children2).each do |child1, child2|
        child_result = compare_nodes(child1, child2, opts, child_opts,
                                     diff_children, differences)
        result = child_result unless child_result == Comparison::EQUIVALENT
      end
      return result
    end
  end

  # Check if nodes should be excluded
  return Comparison::EQUIVALENT if node_excluded?(n1, opts) &&
    node_excluded?(n2, opts)

  if node_excluded?(n1, opts) || node_excluded?(n2, opts)
    add_difference(n1, n2, Comparison::MISSING_NODE,
                   Comparison::MISSING_NODE, :text_content, opts, differences)
    return Comparison::MISSING_NODE
  end

  # Handle comment vs non-comment comparisons specially
  # Create :comments dimension differences instead of UNEQUAL_NODES_TYPES
  if comment_vs_non_comment_comparison?(n1, n2)
    match_opts = opts[:match_opts]
    comment_behavior = match_opts ? match_opts[:comments] : nil

    # Create a :comments dimension difference
    # The difference will be marked as normative or not based on the profile
    add_difference(n1, n2, Comparison::MISSING_NODE,
                   Comparison::MISSING_NODE, :comments, opts,
                   differences)

    # Return EQUIVALENT if comments are ignored, otherwise return UNEQUAL
    if comment_behavior == :ignore
      Comparison::EQUIVALENT
    else
      Comparison::UNEQUAL_COMMENTS
    end
  elsif !same_node_type?(n1, n2)
    # Check node types match for non-comment comparisons
    add_difference(n1, n2, Comparison::UNEQUAL_NODES_TYPES,
                   Comparison::UNEQUAL_NODES_TYPES, :text_content, opts,
                   differences)
    Comparison::UNEQUAL_NODES_TYPES
  else
    # Dispatch based on node type using NodeTypeComparator strategy
    XmlComparatorHelpers::NodeTypeComparator.compare(
      n1, n2, self, opts, child_opts, diff_children, differences
    )
  end
end

.compare_processing_instruction_nodes(n1, n2, opts, differences) ⇒ Object

Compare processing instruction nodes



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# File 'lib/canon/comparison/xml_comparator.rb', line 493

def compare_processing_instruction_nodes(n1, n2, opts, differences)
  unless n1.target == n2.target
    add_difference(n1, n2, Comparison::UNEQUAL_NODES_TYPES,
                   Comparison::UNEQUAL_NODES_TYPES, :text_content, opts,
                   differences)
    return Comparison::UNEQUAL_NODES_TYPES
  end

  content1 = Canon::XmlParsing.xml_node?(n1) ? n1.content.to_s.strip : ""
  content2 = Canon::XmlParsing.xml_node?(n2) ? n2.content.to_s.strip : ""

  if content1 == content2
    Comparison::EQUIVALENT
  else
    add_difference(n1, n2, Comparison::UNEQUAL_TEXT_CONTENTS,
                   Comparison::UNEQUAL_TEXT_CONTENTS, :text_content,
                   opts, differences)
    Comparison::UNEQUAL_TEXT_CONTENTS
  end
end

.compare_text_nodes(n1, n2, opts, differences) ⇒ Object

Compare text nodes



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# File 'lib/canon/comparison/xml_comparator.rb', line 369

def compare_text_nodes(n1, n2, opts, differences)
  return Comparison::EQUIVALENT if opts[:ignore_text_nodes]

  text1 = node_text(n1)
  text2 = node_text(n2)

  # Use match options
  match_opts = opts[:match_opts]
  behavior = match_opts[:text_content]

  # For HTML, check if text node is inside whitespace-preserving element
  # If so, always use strict comparison regardless of text_content setting
  sensitive_element = should_preserve_whitespace_strictly?(n1, n2, opts)
  if sensitive_element
    behavior = :strict
  end

  # Check if raw content differs
  raw_differs = text1 != text2

  # Check if matches according to behavior
  whitespace_type = match_opts[:whitespace_type] || :strict
  matches_per_behavior = MatchOptions.match_text?(text1, text2,
                                                  behavior,
                                                  whitespace_type: whitespace_type)

  # Determine the correct dimension for this difference
  # - If text_content is :strict, ALL differences use :text_content dimension
  # - If text_content is :normalize, whitespace-only diffs could use :structural_whitespace
  #   but we keep :text_content to ensure correct classification behavior
  # - Otherwise use :text_content
  # However, if element is whitespace-sensitive (like <pre> in HTML),
  # always use :text_content dimension regardless of behavior
  #
  # NOTE: We keep the dimension as :text_content even for whitespace-only diffs
  # when text_content: :normalize. This ensures that the classification uses
  # the text_content behavior (:normalize) instead of structural_whitespace
  # behavior (:strict for XML), which would incorrectly mark the diff as normative.
  if sensitive_element
  # Whitespace-sensitive element: always use :text_content dimension
  else
    # Always use :text_content for text differences
    # This ensures correct classification based on text_content behavior
  end
  dimension = :text_content

  # Create DiffNode in verbose mode when raw content differs
  # This ensures informative diffs are created even for :ignore/:normalize
  if raw_differs && opts[:verbose]
    add_difference(n1, n2, Comparison::UNEQUAL_TEXT_CONTENTS,
                   Comparison::UNEQUAL_TEXT_CONTENTS, dimension,
                   opts, differences)
  end

  # Return based on whether behavior makes difference acceptable
  matches_per_behavior ? Comparison::EQUIVALENT : Comparison::UNEQUAL_TEXT_CONTENTS
end

.equivalent?(n1, n2, opts = {}, child_opts = {}) ⇒ Boolean, Array

Compare two XML nodes for equivalence

Parameters:

  • n1 (String, Moxml::Node) —

    First node

  • n2 (String, Moxml::Node) —

    Second node

  • opts (Hash) (defaults to: {}) —

    Comparison options

  • child_opts (Hash) (defaults to: {}) —

    Options for child comparison

Returns:

  • (Boolean, Array) —

    true if equivalent, or array of diffs if verbose



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# File 'lib/canon/comparison/xml_comparator.rb', line 44

def equivalent?(n1, n2, opts = {}, child_opts = {})
  # FAST PATH: Object identity - same object is always equivalent
  if n1.equal?(n2)
    return build_trivial_equivalent_result(n1, n2, opts)
  end

  # FAST PATH: String content equality - identical strings are equivalent
  # Skip in verbose mode since caller may need full metadata (e.g. tree_diff statistics)
  if !opts[:verbose] && n1.is_a?(String) && n2.is_a?(String) && n1 == n2
    return true
  end

  opts = DEFAULT_OPTS.merge(opts)

  # Resolve match options with format-specific defaults
  match_opts_hash = MatchOptions::Xml.resolve(
    format: :xml,
    match_profile: opts[:match_profile],
    match: opts[:match],
    preprocessing: opts[:preprocessing],
    global_profile: opts[:global_profile],
    global_options: opts[:global_options],
  )

  # Wrap in ResolvedMatchOptions for DiffClassifier
  match_opts = Canon::Comparison::ResolvedMatchOptions.new(
    match_opts_hash,
    format: :xml,
  )

  # Store resolved match options hash for use in comparison logic
  opts[:match_opts] = match_opts_hash

  # FAST PATH: leptris Merkle digest — equal root-subtree
  # digests plus identical document-level skeletons prove
  # content identity (modulo whitespace-only text nodes and
  # attribute order), which implies equivalence wherever
  # canon's whitespace handling is the same symmetric
  # parse-time strip. Callers whose whitespace semantics
  # differ from that skip the gate: strict attribute order
  # (invisible to the digest), user-configured whitespace
  # element lists, xml:space documents (checked inside the
  # gate), and verbose callers who need the report.
  if !(opts[:verbose] ||
         match_opts_hash[:attribute_order] == :strict ||
         match_opts_hash[:preserve_whitespace_elements] ||
         match_opts_hash[:collapse_whitespace_elements] ||
         match_opts_hash[:strip_whitespace_elements]) &&
      Xml::DigestGate.equal?(n1, n2)
    return true
  end

  # Create child_opts with resolved options
  child_opts = opts.merge(child_opts)

  # Determine if we should preserve whitespace during parsing.
  # Only structural_whitespace: :strict forces whitespace-only text
  # nodes to survive parsing.  whitespace_type is about distinguishing
  # Unicode whitespace *types* in surviving text-node content, and
  # does NOT require indent text nodes to be kept — libxml's NOBLANKS
  # only strips pure-ASCII whitespace-only nodes, so NBSP-only nodes
  # survive regardless.  Coupling whitespace_type: :strict to
  # parsing-time preservation made pretty-printed fixtures produce
  # spurious element-position diffs (issue #112).
  preserve_whitespace = match_opts_hash[:structural_whitespace] == :strict

  # Parse nodes if they are strings, applying preprocessing if needed
  node1 = parse_node(n1, match_opts_hash[:preprocessing],
                     preserve_whitespace: preserve_whitespace)
  node2 = parse_node(n2, match_opts_hash[:preprocessing],
                     preserve_whitespace: preserve_whitespace)

  # Store original strings for line diff display (before preprocessing)
  original1 = n1.is_a?(String) ? n1 : serialize_node(n1)
  original2 = n2.is_a?(String) ? n2 : serialize_node(n2)

  differences = []
  diff_children = opts[:diff_children] || false

  result = compare_nodes(node1, node2, opts, child_opts,
                         diff_children, differences)

  # Classify DiffNodes as normative/informative if we have verbose output
  if opts[:verbose] && !differences.empty?
    classifier = Canon::Diff::DiffClassifier.new(match_opts)
    classifier.classify_all(differences.grep(Canon::Diff::DiffNode))
  end

  if opts[:verbose]
    # Serialize parsed nodes for consistent formatting
    # This ensures both sides formatted identically, showing only real differences
    preprocessed = [
      serialize_node(node1).gsub("><", ">\n<"),
      serialize_node(node2).gsub("><", ">\n<"),
    ]

    ComparisonResult.new(
      differences: differences,
      preprocessed_strings: preprocessed,
      original_strings: [original1, original2],
      format: :xml,
      match_options: match_opts_hash,
      algorithm: :dom,
      parse_errors_expected: Comparison.parse_errors_for(node1),
      parse_errors_received: Comparison.parse_errors_for(node2),
    )
  elsif result != Comparison::EQUIVALENT && !differences.empty?
    # Non-verbose mode: check equivalence
    # If comparison found differences, classify them to determine if normative
    classifier = Canon::Diff::DiffClassifier.new(match_opts)
    classifier.classify_all(differences.grep(Canon::Diff::DiffNode))
    # Equivalent if no normative differences (matches semantic algorithm)
    differences.none?(&:normative?)
  else
    # Either equivalent or no differences tracked
    result == Comparison::EQUIVALENT
  end
end

.extract_element_path(node) ⇒ Array<String>

Extract element path for context (best effort)

Parameters:

  • node (Object) —

    Node to extract path from

Returns:

  • (Array<String>) —

    Path components



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# File 'lib/canon/comparison/xml_comparator.rb', line 545

def extract_element_path(node)
  path = []
  current = node
  max_depth = 20
  depth = 0

  while current && depth < max_depth
    n = if current.is_a?(Canon::Xml::Node)
          current.name
        elsif Canon::XmlParsing.xml_node?(current)
          current.name
        end
    path.unshift(n) if n

    break unless Canon::XmlParsing.xml_node?(current) || current.is_a?(Canon::Xml::Node)

    current = current.parent
    depth += 1

    break if Canon::XmlParsing.document?(current)
  end

  path
end

.in_preserve_element?(node, preserve_list) ⇒ Boolean

Check if a node is inside a whitespace-preserving element

Returns:

  • (Boolean) 


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# File 'lib/canon/comparison/xml_comparator.rb', line 451

def in_preserve_element?(node, preserve_list)
  current = node.parent
  while Canon::XmlParsing.xml_node?(current) || current.is_a?(Canon::Xml::Node)
    return true if preserve_list.include?(current.name.downcase)

    break if Canon::XmlParsing.document?(current)

    current = current.parent
    break unless current
  end
  false
end

.parse(node, preprocessing = :none, preserve_whitespace: false) ⇒ Object

Public parsing API for external callers



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# File 'lib/canon/comparison/xml_comparator.rb', line 210

def parse(node, preprocessing = :none, preserve_whitespace: false)
  parse_node(node, preprocessing,
             preserve_whitespace: preserve_whitespace)
end

.should_preserve_whitespace_strictly?(n1, n2, opts) ⇒ Boolean

Check if whitespace should be preserved strictly for these text nodes This applies to HTML elements like pre, code, textarea, script, style and elements with xml:space="preserve" or in user-configured preserve list.

IMPORTANT: This returns true ONLY for :preserve classification. For :collapse classification, whitespace differences ARE acceptable (they are detected as formatting-only by DiffClassifier).

Returns:

  • (Boolean) 


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# File 'lib/canon/comparison/xml_comparator.rb', line 434

def should_preserve_whitespace_strictly?(n1, n2, opts)
  # Check both n1 and n2 - if either is in a preserve whitespace element, preserve strictly
  [n1, n2].each do |node|
    next unless Canon::XmlParsing.xml_node?(node) || node.is_a?(Canon::Xml::Node)

    parent = node.parent
    next unless parent

    classification = WhitespaceSensitivity.classify_element(parent,
                                                            opts[:match_opts])
    return true if classification == :preserve
  end

  false
end