[diffoscope] 01/01: diffoscope.tools: Add internal documentation for @tool_required decorator.

[Chris Lamb]

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lamby pushed a commit to branch experimental
in repository diffoscope.

commit e77b9299efbfdf0f64d8fc81470b4f96d24ccb18
Author: Chris Lamb <lamby at debian.org>
Date:   Tue Mar 28 21:44:54 2017 +0100

    diffoscope.tools: Add internal documentation for @tool_required decorator.
    
    Signed-off-by: Chris Lamb <lamby at debian.org>
---
 diffoscope/tools.py | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/diffoscope/tools.py b/diffoscope/tools.py
index 15d7a60..2882b01 100644
--- a/diffoscope/tools.py
+++ b/diffoscope/tools.py
@@ -52,6 +52,16 @@ def tool_required(command):
     def wrapper(fn):
         @functools.wraps(fn)
         def tool_check(*args, **kwargs):
+            """
+            Due to the way decorators are executed at import-time we defer the
+            execution of `find_executable` until we actually run the decorated
+            function (instead of prematurely returning a different version of
+            `tool_check`).
+
+            This ensures that any os.environ['PATH'] modifications are
+            performed prior to the `find_executable` tests.
+            """
+
             if not find_executable(command):
                 raise RequiredToolNotFound(command)
 

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