bundle/commands/exec: improve PATH handling.

- don't add `pkg-config` to the PATH, it's not needed as a shim already
  exists in Homebrew for this and we're overriding it here
- any package with a version specified in an environment variable should
  be prepended to the PATH, not appended

Author: MikeMcQuaid

lib/bundle/commands/exec.rb

@@ -4,6 +4,7 @@
 require "exceptions"
 require "extend/ENV"
 require "utils"
+require "PATH"
 
 module Bundle
   module Commands
@@ -98,10 +99,6 @@ def run(*args, global: false, file: nil, subcommand: "")
           ENV.prepend_path "PATH", Pathname.new(dep_root)/"shims"
         end
 
-        # Setup pkg-config, if present, to help locate packages
-        pkgconfig = Formulary.factory("pkg-config")
-        ENV.prepend_path "PATH", pkgconfig.opt_bin.to_s if pkgconfig.any_version_installed?
-
         # Ensure the Ruby path we saved goes before anything else, if the command was in the PATH
         ENV.prepend_path "PATH", command_path if command_path.present?
 
@@ -122,7 +119,21 @@ def run(*args, global: false, file: nil, subcommand: "")
             opt = %r{/opt/#{formula_name}([/:$])}
             next unless value.match(opt)
 
-            ENV[key] = value.gsub(opt, "/Cellar/#{formula_name}/#{formula_version}\\1")
+            cellar = "/Cellar/#{formula_name}/#{formula_version}\\1"
+
+            if key == "PATH"
+              rejected_opts = []
+              path = PATH.new(ENV.fetch("PATH"))
+                         .reject do |value|
+                rejected_opts << value if value.match?(opt)
+              end
+              rejected_opts.each do |value|
+                path.prepend(value.gsub(opt, cellar))
+              end
+              ENV["PATH"] = path.to_s
+            else
+              ENV[key] = value.gsub(opt, cellar)
+            end
           end
         end
 

spec/stub/PATH.rb

@@ -0,0 +1,28 @@
+# frozen_string_literal: true
+
+class PATH
+  def initialize(*paths)
+    @paths = parse(paths)
+  end
+
+  def prepend(*paths)
+    @paths = parse(paths + @paths)
+  end
+
+  def reject(&block)
+    self.class.new(@paths.reject(&block))
+  end
+
+  def to_s
+    @paths.join(File::PATH_SEPARATOR)
+  end
+
+  private
+
+  def parse(paths)
+    paths.flatten
+         .compact
+         .flat_map { |p| Pathname(p).to_path.split(File::PATH_SEPARATOR) }
+         .uniq
+  end
+end