From d2f75170a6c1548b85335c7e84a000ed67a0158b Mon Sep 17 00:00:00 2001
From: Eric Wong <normalperson@yhbt.net>
Date: Sat, 7 Sep 2013 21:25:17 +0000
Subject: implement environment variable expansion

This will allow users to more-easily edit configs and feel
like a real shell.  We no longer mistakenly expand nil env
variables to "" anymore, either.
---
 lib/dtas/process.rb         | 28 ++++++++++++++++++++---
 lib/dtas/source/sox.rb      |  2 +-
 test/test_env.rb            | 55 +++++++++++++++++++++++++++++++++++++++++++++
 test/test_rg_integration.rb |  3 +--
 4 files changed, 82 insertions(+), 6 deletions(-)
 create mode 100644 test/test_env.rb

diff --git a/lib/dtas/process.rb b/lib/dtas/process.rb
index b90b318..a3c1c04 100644
--- a/lib/dtas/process.rb
+++ b/lib/dtas/process.rb
@@ -19,12 +19,33 @@ module DTAS::Process # :nodoc:
     end while true
   end
 
+  # expand common shell constructs based on environment variables
+  # this is order-dependent, but Ruby 1.9+ hashes are already order-dependent
+  def env_expand(env, opts)
+    env = env.dup
+    if false == opts.delete(:expand)
+      env.each do |key, val|
+        Numeric === val and env[key] = val.to_s
+      end
+    else
+      env.each do |key, val|
+        case val
+        when Numeric # stringify numeric values to simplify users' lives
+          env[key] = val.to_s
+        when /[\`\$]/ # perform variable/command expansion
+          tmp = env.dup
+          tmp.delete(key)
+          val = qx(tmp, "echo #{val}", expand: false)
+          env[key] = val.chomp
+        end
+      end
+    end
+  end
+
   # for long-running processes (sox/play/ecasound filters)
   def dtas_spawn(env, cmd, opts)
     opts = { close_others: true, pgroup: true }.merge!(opts)
-
-    # stringify env, integer values are easier to type unquoted as strings
-    env.each { |k,v| env[k] = v.to_s }
+    env = env_expand(env, opts)
 
     pid = begin
       Process.spawn(env, cmd, opts)
@@ -53,6 +74,7 @@ module DTAS::Process # :nodoc:
       re.binmode
       opts[:err] = we
     end
+    env = env_expand(env, opts)
     pid = begin
       Process.spawn(env, *cmd, opts)
     rescue Errno::EINTR # Ruby bug?
diff --git a/lib/dtas/source/sox.rb b/lib/dtas/source/sox.rb
index e26f54b..484a0ec 100644
--- a/lib/dtas/source/sox.rb
+++ b/lib/dtas/source/sox.rb
@@ -41,7 +41,7 @@ class DTAS::Source::Sox # :nodoc:
   def try(infile, offset = nil)
     err = ""
     cmd = %W(soxi -s #{infile})
-    s = qx(@env, cmd, err_str: err, no_raise: true)
+    s = qx(@env.dup, cmd, err_str: err, no_raise: true)
     return if err =~ /soxi FAIL formats:/
     self.class.try_to_fail_harder(infile, s, cmd) or return
     source_file_dup(infile, offset)
diff --git a/test/test_env.rb b/test/test_env.rb
new file mode 100644
index 0000000..92fc53c
--- /dev/null
+++ b/test/test_env.rb
@@ -0,0 +1,55 @@
+# Copyright (C) 2013, Eric Wong <normalperson@yhbt.net> and all contributors
+# License: GPLv3 or later (https://www.gnu.org/licenses/gpl-3.0.txt)
+require_relative 'helper'
+require 'dtas/process'
+class TestEnv < Testcase
+  include DTAS::Process
+  def setup
+    @orig = ENV.to_hash
+  end
+
+  def teardown
+    ENV.clear
+    ENV.update(@orig)
+  end
+
+  def test_expand
+    ENV["HELLO"] = 'HIHI'
+    expect = { "BLAH" => "HIHI/WORLD" }
+    opts = {}
+
+    env = { "BLAH" => "$HELLO/WORLD" }
+    assert_equal(expect, env_expand(env, opts))
+
+    env = { "BLAH" => "${HELLO}/WORLD" }
+    assert_equal(expect, env_expand(env, opts))
+
+    env = { "BLAH" => "$(echo $HELLO)/WORLD" }
+    assert_equal(expect, env_expand(env, opts))
+
+    env = { "BLAH" => "`echo $HELLO/WORLD`" }
+    assert_equal(expect, env_expand(env, opts))
+
+    env = { "BLAH" => "HIHI/WORLD" }
+    assert_equal(expect, env_expand(env, opts))
+
+    # disable expansion
+    env = expect = { "BLAH" => "`echo $HELLO/WORLD`" }
+    assert_equal(expect, env_expand(env, expand: false))
+
+    # numeric expansion always happens
+    env = { "BLAH" => 1 }
+    assert_equal({"BLAH"=>"1"}, env_expand(env, expand: false))
+    env = { "BLAH" => 1 }
+    assert_equal({"BLAH"=>"1"}, env_expand(env, {}))
+
+    expect = { "BLAH" => nil }
+    env = expect.dup
+    assert_equal expect, env_expand(env, expand:false)
+    assert_equal expect, env_expand(env, expand:true)
+
+    # recursive expansion
+    res = env_expand({"PATH"=>"$PATH"}, expand: true)
+    assert_equal ENV["PATH"], res["PATH"]
+  end
+end
diff --git a/test/test_rg_integration.rb b/test/test_rg_integration.rb
index d6a90b0..2779f86 100644
--- a/test/test_rg_integration.rb
+++ b/test/test_rg_integration.rb
@@ -40,7 +40,7 @@ class TestRgIntegration < Testcase
       end while cur["current_offset"] == 0 && sleep(0.01)
     end
 
-    assert_empty cur["current"]["env"]["RGFX"]
+    assert_nil cur["current"]["env"]["RGFX"]
 
     assert_equal DTAS::Format.new.rate * len, cur["current_expect"]
 
@@ -119,7 +119,6 @@ class TestRgIntegration < Testcase
       "REPLAYGAIN_ALBUM_GAIN" => "-3.0",
       "REPLAYGAIN_TRACK_PEAK" => "0.666",
       "REPLAYGAIN_ALBUM_PEAK" => "0.999",
-      "REPLAYGAIN_REFERENCE_LOUDNESS" => nil
     }
     assert_equal expect, rg
   end
-- 
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