Small refactoring of parser to make it easier to grok

lib/dotenv/parser.rb

@@ -8,8 +8,10 @@ class FormatError < SyntaxError; end
   # Parses the `.env` file format into key/value pairs.
   # It allows for variable substitutions, command substitutions, and exporting of variables.
   class Parser
-    @substitutions =
-      [Dotenv::Substitutions::Variable, Dotenv::Substitutions::Command]
+    @substitutions = [
+      Dotenv::Substitutions::Variable,
+      Dotenv::Substitutions::Command
+    ]
 
     LINE = /
       (?:^|\A)              # beginning of line
@@ -40,15 +42,16 @@ def call(...)
     def initialize(string, overwrite: false)
       @string = string
       @hash = {}
-      @variables_to_ignore = overwrite ? nil : ENV.except("DOTENV_LINEBREAK_MODE")
+      @overwrite = overwrite
     end
 
     def call
       # Convert line breaks to same format
       lines = @string.gsub(/\r\n?/, "\n")
       # Process matches
       lines.scan(LINE).each do |key, value|
-        next if @variables_to_ignore&.include?(key)
+        # Skip parsing values that will be ignored
+        next if ignore?(key)
 
         @hash[key] = parse_value(value || "")
       end
@@ -61,6 +64,11 @@ def call
 
     private
 
+    # Determine if the key can be ignored.
+    def ignore?(key)
+      !@overwrite && key != "DOTENV_LINEBREAK_MODE" && ENV.key?(key)
+    end
+
     def parse_line(line)
       if line.split.first == "export"
         if variable_not_set?(line)
@@ -69,12 +77,22 @@ def parse_line(line)
       end
     end
 
+    QUOTED_STRING = /\A(['"])(.*)\1\z/m
     def parse_value(value)
       # Remove surrounding quotes
-      value = value.strip.sub(/\A(['"])(.*)\1\z/m, '\2')
+      value = value.strip.sub(QUOTED_STRING, '\2')
       maybe_quote = Regexp.last_match(1)
-      value = unescape_value(value, maybe_quote)
-      perform_substitutions(value, maybe_quote)
+
+      # Expand new lines in double quoted values
+      value = expand_newlines(value) if maybe_quote == '"'
+
+      # Unescape characters and performs substitutions unless value is single quoted
+      if maybe_quote != "'"
+        value = unescape_characters(value)
+        self.class.substitutions.each { |proc| value = proc.call(value, @hash) }
+      end
+
+      value
     end
 
     def unescape_characters(value)
@@ -92,24 +110,5 @@ def expand_newlines(value)
     def variable_not_set?(line)
       !line.split[1..].all? { |var| @hash.member?(var) }
     end
-
-    def unescape_value(value, maybe_quote)
-      if maybe_quote == '"'
-        unescape_characters(expand_newlines(value))
-      elsif maybe_quote.nil?
-        unescape_characters(value)
-      else
-        value
-      end
-    end
-
-    def perform_substitutions(value, maybe_quote)
-      if maybe_quote != "'"
-        self.class.substitutions.each do |proc|
-          value = proc.call(value, @hash)
-        end
-      end
-      value
-    end
   end
 end

lib/dotenv/substitutions/variable.rb

@@ -12,7 +12,7 @@ class << self
         VARIABLE = /
           (\\)?         # is it escaped with a backslash?
           (\$)          # literal $
-          (?!\()        # shouldnt be followed by paranthesis
+          (?!\()        # shouldn't be followed by parenthesis
           \{?           # allow brace wrapping
           ([A-Z0-9_]+)? # optional alpha nums
           \}?           # closing brace
@@ -21,19 +21,14 @@ class << self
         def call(value, env)
           value.gsub(VARIABLE) do |variable|
             match = $LAST_MATCH_INFO
-            substitute(match, variable, env)
-          end
-        end
-
-        private
 
-        def substitute(match, variable, env)
-          if match[1] == "\\"
-            variable[1..]
-          elsif match[3]
-            env[match[3]] || ENV[match[3]] || ""
-          else
-            variable
+            if match[1] == "\\"
+              variable[1..]
+            elsif match[3]
+              env[match[3]] || ENV[match[3]] || ""
+            else
+              variable
+            end
           end
         end
       end