Resolves #4246, use recursive descent parser to implement ifeval

lib/asciidoctor.rb

@@ -570,6 +570,7 @@ def self.const_missing name
 require_relative 'asciidoctor/stylesheets'
 require_relative 'asciidoctor/table'
 require_relative 'asciidoctor/writer'
+require_relative 'asciidoctor/ifeval_parser'
 
 # main API entry points
 require_relative 'asciidoctor/load'

lib/asciidoctor/ifeval_parser.rb

@@ -0,0 +1,197 @@
+module Asciidoctor
+
+
+# The recursive descent parser for asciidoctor-pdf's ifeval
+#
+# EBNF expression LL(*):
+#   expr := disjunction
+#   disjunction := conjunction ('or' conjunction)*
+#   conjunction := inversion ('and' inversion)*
+#   inversion := 'not' inversion
+#              | comparison
+#
+#   comparison := term "==" term
+#               | term "!=" term
+#               | term ">" term
+#               | term "<" term
+#               | term "<=" term
+#               | term ">=" term
+#   term := literal
+#       | '(' expr ')'
+#
+# reference:
+#   https://docs.python.org/3/reference/grammar.html
+
+class IfevalParser
+  include Logging
+
+  @str = ""
+  @pos = 0
+  @next_pos = 0
+  @document
+
+  def initialize doc
+    @str = ""
+    @pos = 0
+    @next_pos = 0
+    @document = doc
+  end
+
+  def peek_token
+    @next_pos = @pos
+    str = @str[@pos..-1]
+    if str =~ /^\s*\d+/ ||                         # for number
+       str =~ /^\s*[+\-*\/()]/ ||            # for operator
+       str =~ /^\s*(==|!=|>=|<=|>|<)/ ||     # for equivalent
+       str =~ /^\s*"\S*?"/ ||                 # for string
+       str =~ /^\s*{\S*?}/ ||                 # for attribute
+       str =~ /^\s*(not|and|or|true|false)/  # for binary operator
+      token = $~[0]
+      @next_pos += token.length
+#      puts @str[@next_pos..-1]
+      return token.gsub(/\s*/, "")
+    end
+
+    nil
+  end
+
+  def commit_token
+    @pos = @next_pos
+  end
+
+  def solve str
+    initialize @document
+    @str = str
+    next_expr
+  end
+
+  def next_expr
+    next_disjunction
+  end
+
+  def next_disjunction
+    a = next_conjunction
+    token = peek_token
+    while token == "or"
+      commit_token
+      b = next_conjunction
+      token = peek_token
+      a = a | b
+    end
+    return a
+  end
+
+  def next_conjunction
+    a = next_inversion
+    token = peek_token
+    while token == "and"
+      commit_token
+      b = next_inversion
+      token = peek_token
+      a = a & b
+    end
+    return a
+  end
+
+  def next_inversion
+    token = peek_token
+    if token == "not"
+      commit_token
+      ret = next_inversion
+      return !ret
+    end
+
+    return next_comparison
+  end
+
+  def next_comparison
+    a = next_term
+    token = peek_token
+    if token == "=="
+      commit_token
+      b = next_term
+      return a == b
+    elsif token == "!="
+      commit_token
+      b = next_term
+      return a != b
+    elsif token == ">="
+      commit_token
+      b = next_term
+      return a >= b
+    elsif token == "<="
+      commit_token
+      b = next_term
+      return a <= b
+    elsif token == ">"
+      commit_token
+      b = next_term
+      return a > b
+    elsif token == "<"
+      commit_token
+      b = next_term
+      return a < b
+    else
+      return a
+    end
+  end
+
+  def next_term
+    token = peek_token
+    commit_token
+    if token == "("
+      a = next_expr
+      token = peek_token
+      commit_token
+      if token != ")"
+        raise ArgumentError, "Expect ')', but is #{token}"
+      end
+      token = a
+    end
+
+    # literal
+    resolve_expr_val token
+#    if token.to_s =~ /(true|false)/ 
+#      return token.to_s == "true"
+#    elsif token.to_s =~ /"(\S+)"/
+#      return $1
+#    else
+#      return token
+#    end
+  end
+
+  def resolve_expr_val val
+    if ((val.start_with? '"') && (val.end_with? '"')) ||
+        ((val.start_with? '\'') && (val.end_with? '\''))
+      quoted = true
+      val = val.gsub(/"(.+)"/, '\1')
+      val = val.gsub(/'(.+)'/, '\1')
+    else
+      quoted = false
+    end
+
+    # QUESTION should we substitute first?
+    # QUESTION should we also require string to be single quoted (like block attribute values?)
+    val = @document.sub_attributes val, attribute_missing: 'drop' if val.include? ATTR_REF_HEAD
+
+    if quoted
+      val = val.gsub(/"(.+)"/, '\1')
+      val
+    elsif val.empty?
+      nil
+    elsif val == 'true'
+      true
+    elsif val == 'false'
+      false
+    elsif val.rstrip.empty?
+      ' '
+    elsif val.include? '.'
+      val.to_f
+    else
+      # fallback to coercing to integer, since we
+      # require string values to be explicitly quoted
+      val.to_i
+    end
+  end
+end
+end

lib/asciidoctor/reader.rb

@@ -935,18 +935,7 @@ def preprocess_conditional_directive keyword, target, delimiter, text
         end
       when 'ifeval'
         if no_target
-          # the text in brackets must match a conditional expression
-          if text && EvalExpressionRx =~ text.strip
-            # NOTE assignments must happen before call to resolve_expr_val for compatibility with Opal
-            lhs = $1
-            # regex enforces a restricted set of math-related operations (==, !=, <=, >=, <, >)
-            op = $2
-            rhs = $3
-            skip = ((resolve_expr_val lhs).send op, (resolve_expr_val rhs)) ? false : true rescue true
-          else
-            logger.error message_with_context %(malformed preprocessor directive - #{text ? 'invalid expression' : 'missing expression'}: ifeval::[#{text}]), source_location: cursor
-            return true
-          end
+            skip = !(conditional_ifeval text)
         else
           logger.error message_with_context %(malformed preprocessor directive - target not permitted: ifeval::#{target}[#{text}]), source_location: cursor
           return true
@@ -973,6 +962,17 @@ def preprocess_conditional_directive keyword, target, delimiter, text
     true
   end
 
+  def conditional_ifeval text
+    # the text in brackets must match a conditional expression
+    if text && EvalExpressionRx =~ text.strip
+      parser = IfevalParser.new @document
+      return parser.solve text
+    else
+      logger.error message_with_context %(malformed preprocessor directive - #{text ? 'invalid expression' : 'missing expression'}: ifeval::[#{text}]), source_location: cursor
+      return true
+    end
+  end
+
   # Internal: Preprocess the directive to include lines from another document.
   #
   # Preprocess the directive to include the target document. The scenarios
@@ -1325,7 +1325,8 @@ def resolve_expr_val val
     if ((val.start_with? '"') && (val.end_with? '"')) ||
         ((val.start_with? '\'') && (val.end_with? '\''))
       quoted = true
-      val = val.slice 1, (val.length - 1)
+      val = val.gsub(/"(.+)"/, '\1')
+      val = val.gsub(/'(.+)'/, '\1')
     else
       quoted = false
     end
@@ -1335,6 +1336,7 @@ def resolve_expr_val val
     val = @document.sub_attributes val, attribute_missing: 'drop' if val.include? ATTR_REF_HEAD
 
     if quoted
+      val = val.gsub(/"(.+)"/, '\1')
       val
     elsif val.empty?
       nil