From 23a38e0ff6beb26f86eca0c56b25d6100375b60d Mon Sep 17 00:00:00 2001
From: ilovezfs
Date: Fri, 5 Aug 2016 00:20:20 -0700
Subject: virtualenv_install_with_resources: select correct python

`virtualenv_install_with_resources` will now attempt to guess the
desired Python based on the active build options and based on the
dependencies and requirements. When the situation is ambiguous (e.g.,
`depends_on :python3` and `build.with? "python"` is true) raise
`FormulaAmbiguousPythonError` unless `:using => "python"` or
`:using => "python3"` has been passed to resolve the ambiguity.

In most cases, this will allow

```
    virtualenv_create(libexec, "python3")
    virtualenv_install_with_resources
```

to be changed to just

```
    virtualenv_install_with_resources
```
---
 Library/Homebrew/language/python.rb | 28 +++++++++++++++++++++++++---
 1 file changed, 25 insertions(+), 3 deletions(-)

(limited to 'Library/Homebrew/language/python.rb')

diff --git a/Library/Homebrew/language/python.rb b/Library/Homebrew/language/python.rb
index 95259c841..b28b1ca60 100644
--- a/Library/Homebrew/language/python.rb
+++ b/Library/Homebrew/language/python.rb
@@ -139,11 +139,33 @@ module Language
         venv
       end
 
+      # Returns true if a formula option for the specified python is currently
+      # active or if the specified python is required by the formula. Valid
+      # inputs are "python", "python3", :python, and :python3. Note that
+      # "with-python", "without-python", "with-python3", and "without-python3"
+      # formula options are handled correctly even if not associated with any
+      # corresponding depends_on statement.
+      # @api private
+      def needs_python?(python)
+        return true if build.with?(python)
+        (requirements.to_a | deps).any? { |r| r.name == python && r.required? }
+      end
+
       # Helper method for the common case of installing a Python application.
       # Creates a virtualenv in `libexec`, installs all `resource`s defined
-      # on the formula, and then installs the formula.
-      def virtualenv_install_with_resources
-        venv = virtualenv_create(libexec)
+      # on the formula, and then installs the formula. An options hash may be
+      # passed (e.g., :using => "python3") to override the default, guessed
+      # formula preference for python or python3, or to resolve an ambiguous
+      # case where it's not clear whether python or python3 should be the
+      # default guess.
+      def virtualenv_install_with_resources(options = {})
+        python = options[:using]
+        if python.nil?
+          wanted = %w[python python3].select { |py| needs_python?(py) }
+          raise FormulaAmbiguousPythonError, self if wanted.size > 1
+          python = wanted.first || "python"
+        end
+        venv = virtualenv_create(libexec, python)
         venv.pip_install resources
         venv.pip_install_and_link buildpath
         venv
-- 
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