Changeset 11041

Timestamp:

Dec 14, 2011, 9:19:06 PM (12 years ago)

Author:

Steffen Hoffmann

Message:

TagsPlugin: Prevent AttributeError on environment startup for Trac 0.13dev, refs #9521.

Additionally this broke all environment upgrades for plugins and for
Trac core itself, at least as long as the plugin was installed and enabled.

While this might be just a temporary Trac behavior (see Remy Blank's
​comment in ticket #10451), it prevails in trunk
for more than a month now - a major headache for early adopters.
So I feel like acting now, facing the risk of not fixing it properly.

The logical next step is switching to the recommended procedure of storing
explicite db schema versions inside the Trac db like other plugins already do.

File:

• tagsplugin/trunk/tractags/model.py (modified) (4 diffs)

tagsplugin/trunk/tractags/model.py

@@ -1 @@
-from trac.core import *
+from trac.core import Component, TracError, implements
 from trac.env import IEnvironmentSetupParticipant
 from trac.db import Table, Column, Index
+from trac.db.api import DatabaseManager
 
 
 class TagModelProvider(Component):
+
     implements(IEnvironmentSetupParticipant)
 
@@ -15 +17 @@
               Index(['tagspace', 'tag']),]
         ]
+    def __init__(self):
+        # Preemptive check for rollback tolerance of read-only db connections.
+        # This is required to avoid breaking `environment_needs_upgrade`,
+        #   if the plugin uses intentional db transaction errors for the test.
+        self.rollback_is_safe = True
+        try:
+            db = DatabaseManager(self.env).get_connection()
+            if hasattr(db, 'readonly'):
+                db = DatabaseManager(self.env).get_connection(readonly=True)
+                cursor = db.cursor()
+                # Test needed for rollback on read-only connections.
+                cursor.execute("SELECT COUNT(*) FROM system")
+                cursor.fetchone()
+                try:
+                    db.rollback()
+                except AttributeError:
+                    # Avoid rollback on read-only connections.
+                    self.rollback_is_safe = False
+                    return
+                # Test passed.
+        except TracError, e:
+            # Trac too old - expect no constraints.
+            return
 
     # IEnvironmentSetupParticipant methods
@@ -30 +55 @@
         except Exception, e:
             self.log.error("DatabaseError: %s", e)
-            db.rollback()
+            if self.rollback_is_safe:
+                db.rollback()
             return True
 
@@ -44 +70 @@
             return True
         except Exception, e:
-            # The expected outcome for any new/updated installation.
-            db.rollback()
+            # The expected outcome for any up-to-date installation.
+            if self.rollback_is_safe:
+                db.rollback()
             return False