Merge pull request #515 from andrewts129/andrewts129/faster-parsing

Optimize parser by removing repeated hash merges

Gemfile

@@ -3,6 +3,8 @@ gemspec name: "dotenv"
 gemspec name: "dotenv-rails"
 
 gem "railties", "~> #{ENV["RAILS_VERSION"] || "7.1"}"
+gem "benchmark-ips"
+gem "stackprof"
 
 group :guard do
   gem "guard-rspec"

benchmark/parse_ips.rb

@@ -0,0 +1,15 @@
+require "bundler/setup"
+require "dotenv"
+require "benchmark/ips"
+require "tempfile"
+
+f = Tempfile.create("benchmark_ips.env")
+1000.times.map { |i| f.puts "VAR_#{i}=#{i}" }
+f.close
+
+Benchmark.ips do |x|
+  x.report("parse, overwrite:false") { Dotenv.parse(f.path, overwrite: false) }
+  x.report("parse, overwrite:true") { Dotenv.parse(f.path, overwrite: true) }
+end
+
+File.unlink(f.path)

benchmark/parse_profile.rb

@@ -0,0 +1,23 @@
+require "bundler/setup"
+require "dotenv"
+require "stackprof"
+require "benchmark/ips"
+require "tempfile"
+
+f = Tempfile.create("benchmark_ips.env")
+1000.times.map { |i| f.puts "VAR_#{i}=#{i}" }
+f.close
+
+profile = StackProf.run(mode: :wall, interval: 1_000) do
+  10_000.times do
+    Dotenv.parse(f.path, overwrite: false)
+  end
+end
+
+result = StackProf::Report.new(profile)
+puts
+result.print_text
+puts "\n\n\n"
+result.print_method(/Dotenv.parse/)
+
+File.unlink(f.path)

lib/dotenv/parser.rb

@@ -40,14 +40,16 @@ def call(...)
     def initialize(string, overwrite: false)
       @string = string
       @hash = {}
-      @overwrite = overwrite
+      @variables_to_ignore = overwrite ? nil : ENV.except("DOTENV_LINEBREAK_MODE")
     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)
+
         @hash[key] = parse_value(value || "")
       end
       # Process non-matches
@@ -104,7 +106,7 @@ def unescape_value(value, maybe_quote)
     def perform_substitutions(value, maybe_quote)
       if maybe_quote != "'"
         self.class.substitutions.each do |proc|
-          value = proc.call(value, @hash, overwrite: @overwrite)
+          value = proc.call(value, @hash)
         end
       end
       value

lib/dotenv/substitutions/command.rb

@@ -20,7 +20,7 @@ class << self
           )
         /x
 
-        def call(value, _env, overwrite: false)
+        def call(value, _env)
           # Process interpolated shell commands
           value.gsub(INTERPOLATED_SHELL_COMMAND) do |*|
             # Eliminate opening and closing parentheses

lib/dotenv/substitutions/variable.rb

@@ -18,11 +18,10 @@ class << self
           \}?           # closing brace
         /xi
 
-        def call(value, env, overwrite: false)
-          combined_env = overwrite ? ENV.to_h.merge(env) : env.merge(ENV)
+        def call(value, env)
           value.gsub(VARIABLE) do |variable|
             match = $LAST_MATCH_INFO
-            substitute(match, variable, combined_env)
+            substitute(match, variable, env)
           end
         end
 
@@ -32,7 +31,7 @@ def substitute(match, variable, env)
           if match[1] == "\\"
             variable[1..]
           elsif match[3]
-            env.fetch(match[3], "")
+            env[match[3]] || ENV[match[3]] || ""
           else
             variable
           end