From 72618e374d6055d313f407a2948d50ef079a820d Mon Sep 17 00:00:00 2001
From: Hugo Osvaldo Barrera <hugo@barrera.io>
Date: Mon, 14 Jun 2021 22:50:22 +0200
Subject: [PATCH] Fix double-use of a generation

The first use exhausted it, so the second iteration was empty.
---
 vdirsyncer/cli/fetchparams.py | 17 +++++++++--------
 vdirsyncer/utils.py           |  3 ++-
 2 files changed, 11 insertions(+), 9 deletions(-)

diff --git a/vdirsyncer/cli/fetchparams.py b/vdirsyncer/cli/fetchparams.py
index 3d15119..6a39785 100644
--- a/vdirsyncer/cli/fetchparams.py
+++ b/vdirsyncer/cli/fetchparams.py
@@ -74,20 +74,21 @@ def _fetch_value(opts, key):
         return rv
 
 
-def _strategy_command(*command):
+def _strategy_command(*command: str):
+    """Execute a user-specified command and return its output."""
     import subprocess
 
-    # normalize path of every path member
-    # if there is no path specified then nothing will happen
-    command = map(expand_path, command)
+    # Normalize path of every path member.
+    # If there is no path specified then nothing will happen.
+    # Makes this a list to avoid it being exhausted on the first iteration.
+    expanded_command = list(map(expand_path, command))
 
     try:
-        stdout = subprocess.check_output(command, universal_newlines=True)
+        stdout = subprocess.check_output(expanded_command, universal_newlines=True)
         return stdout.strip("\n")
     except OSError as e:
-        raise exceptions.UserError(
-            "Failed to execute command: {}\n{}".format(" ".join(command), str(e))
-        )
+        cmd = " ".join(expanded_command)
+        raise exceptions.UserError(f"Failed to execute command: {cmd}\n{str(e)}")
 
 
 def _strategy_prompt(text):
diff --git a/vdirsyncer/utils.py b/vdirsyncer/utils.py
index c2130a0..5883030 100644
--- a/vdirsyncer/utils.py
+++ b/vdirsyncer/utils.py
@@ -19,7 +19,8 @@ SAFE_UID_CHARS = (
 _missing = object()
 
 
-def expand_path(p):
+def expand_path(p: str) -> str:
+    """Expand $HOME in a path and normalise slashes."""
     p = os.path.expanduser(p)
     p = os.path.normpath(p)
     return p