Add $cfg_file as an expansion variable for relative paths in the mailman.cfg

file, and improve the error message when an expansion loop is found.  With the
`[mailman]layout: dev` path setting, put $var_dir relative to the mailman.cfg
file.

2 files changed, 16 insertions, 8 deletions

diff --git a/src/mailman/config/config.py b/src/mailman/config/config.py
index e7d8b6b17..1aab4a82a 100644
--- a/src/mailman/config/config.py
+++ b/src/mailman/config/config.py
@@ -46,6 +46,8 @@ from zope.interface import implementer
 
 
 SPACE = ' '
+SPACERS = '\n'
+
 
 MAILMAN_CFG_TEMPLATE = """\
 # AUTOMATICALLY GENERATED BY MAILMAN ON {}
@@ -185,26 +187,32 @@ class Configuration:
             lock_file               = category.lock_file,
             pid_file                = category.pid_file,
             )
+        # Add the path to the .cfg file, if one was given on the command line.
+        if self.filename is not None:
+            substitutions['cfg_file'] = self.filename
         # Now, perform substitutions recursively until there are no more
         # variables with $-vars in them, or until substitutions are not
         # helping any more.
         last_dollar_count = 0
         while True:
+            expandables = []
             # Mutate the dictionary during iteration.
-            dollar_count = 0
-            for key in substitutions.keys():
+            for key in substitutions:
                 raw_value = substitutions[key]
                 value = Template(raw_value).safe_substitute(substitutions)
                 if '$' in value:
                     # Still more work to do.
-                    dollar_count += 1
+                    expandables.append((key, value))
                 substitutions[key] = value
-            if dollar_count == 0:
+            if len(expandables) == 0:
                 break
-            if dollar_count == last_dollar_count:
-                print('Path expansion infloop detected', file=sys.stderr)
+            if len(expandables) == last_dollar_count:
+                print('Path expansion infloop detected:\n',
+                      SPACERS.join('\t{}: {}'.format(key, value)
+                                   for key, value in sorted(expandables)),
+                      file=sys.stderr)
                 sys.exit(1)
-            last_dollar_count = dollar_count
+            last_dollar_count = len(expandables)
         # Ensure that all paths are normalized and made absolute.  Handle the
         # few special cases first.  Most of these are due to backward
         # compatibility.
diff --git a/src/mailman/config/mailman.cfg b/src/mailman/config/mailman.cfg
index 24e81ec91..80da56ddc 100644
--- a/src/mailman/config/mailman.cfg
+++ b/src/mailman/config/mailman.cfg
@@ -25,7 +25,7 @@
 [paths.dev]
 # Convenient development layout where everything is put in the current
 # directory.
-var_dir: var
+var_dir: $cfg_file/../..
 
 [paths.fhs]
 # Filesystem Hiearchy Standard 2.3