Replace jinja2-time with arrow and improve timedate timezone integration, fixes timezones in templates such as {% now 'Europe/London', '%Y-%m-%d' %} etc (#3496)

changedetectionio/jinja2_custom/__init__.py

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+"""
+Jinja2 custom extensions and safe rendering utilities.
+"""
+from .extensions.TimeExtension import TimeExtension
+from .safe_jinja import (
+    render,
+    render_fully_escaped,
+    create_jinja_env,
+    JINJA2_MAX_RETURN_PAYLOAD_SIZE,
+    DEFAULT_JINJA2_EXTENSIONS,
+)
+
+__all__ = [
+    'TimeExtension',
+    'render',
+    'render_fully_escaped',
+    'create_jinja_env',
+    'JINJA2_MAX_RETURN_PAYLOAD_SIZE',
+    'DEFAULT_JINJA2_EXTENSIONS',
+]

changedetectionio/jinja2_custom/extensions/TimeExtension.py

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+"""
+Jinja2 TimeExtension - Custom date/time handling for templates.
+
+This extension provides the {% now %} tag for Jinja2 templates, offering timezone-aware
+date/time formatting with support for time offsets.
+
+Why This Extension Exists:
+    The Arrow library has a now() function (arrow.now()), but Jinja2 templates cannot
+    directly call Python functions - they need extensions or filters to expose functionality.
+
+    This TimeExtension serves as a Jinja2-to-Arrow bridge that:
+
+    1. Makes Arrow accessible in templates - Jinja2 requires registering functions/tags
+       through extensions. You cannot use arrow.now() directly in a template.
+
+    2. Provides template-friendly syntax - Instead of complex Python code, you get clean tags:
+       {% now 'UTC' %}
+       {% now 'UTC' + 'hours=2' %}
+       {% now 'Europe/London', '%Y-%m-%d' %}
+
+    3. Adds convenience features on top of Arrow:
+       - Default timezone from environment variable (TZ) or config
+       - Default datetime format configuration
+       - Offset syntax parsing: 'hours=2,minutes=30' → shift(hours=2, minutes=30)
+       - Empty string timezone support to use configured defaults
+
+    4. Maintains security - Works within Jinja2's sandboxed environment so users
+       cannot access arbitrary Python code or objects.
+
+    Essentially, this is a Jinja2 wrapper around arrow.now() and arrow.shift() that
+    provides user-friendly template syntax while maintaining security.
+
+Basic Usage:
+    {% now 'UTC' %}
+    # Output: Wed, 09 Dec 2015 23:33:01
+
+Custom Format:
+    {% now 'UTC', '%Y-%m-%d %H:%M:%S' %}
+    # Output: 2015-12-09 23:33:01
+
+Timezone Support:
+    {% now 'America/New_York' %}
+    {% now 'Europe/London' %}
+    {% now '' %}  # Uses default timezone from environment.default_timezone
+
+Time Offsets (Addition):
+    {% now 'UTC' + 'hours=2' %}
+    {% now 'UTC' + 'hours=2,minutes=30' %}
+    {% now 'UTC' + 'days=1,hours=2,minutes=15,seconds=10' %}
+
+Time Offsets (Subtraction):
+    {% now 'UTC' - 'minutes=11' %}
+    {% now 'UTC' - 'days=2,minutes=33,seconds=1' %}
+
+Time Offsets with Custom Format:
+    {% now 'UTC' + 'hours=2', '%Y-%m-%d %H:%M:%S' %}
+    # Output: 2015-12-10 01:33:01
+
+Weekday Support (for finding next/previous weekday):
+    {% now 'UTC' + 'weekday=0' %}  # Next Monday (0=Monday, 6=Sunday)
+    {% now 'UTC' + 'weekday=4' %}  # Next Friday
+
+Configuration:
+    - Default timezone: Set via TZ environment variable or override environment.default_timezone
+    - Default format: '%a, %d %b %Y %H:%M:%S' (can be overridden via environment.datetime_format)
+
+Environment Customization:
+    from changedetectionio.jinja2_custom import create_jinja_env
+
+    jinja2_env = create_jinja_env()
+    jinja2_env.default_timezone = 'America/New_York'  # Override default timezone
+    jinja2_env.datetime_format = '%Y-%m-%d %H:%M'      # Override default format
+
+Supported Offset Parameters:
+    - years, months, weeks, days
+    - hours, minutes, seconds, microseconds
+    - weekday (0=Monday through 6=Sunday, must be integer)
+
+Note:
+    This extension uses the Arrow library for timezone-aware datetime handling.
+    All timezone names should be valid IANA timezone identifiers (e.g., 'America/New_York').
+"""
+import arrow
+
+from jinja2 import nodes
+from jinja2.ext import Extension
+import os
+
+class TimeExtension(Extension):
+    """
+    Jinja2 Extension providing the {% now %} tag for timezone-aware date/time rendering.
+
+    This extension adds two attributes to the Jinja2 environment:
+    - datetime_format: Default strftime format string (default: '%a, %d %b %Y %H:%M:%S')
+    - default_timezone: Default timezone for rendering (default: TZ env var or 'UTC')
+
+    Both can be overridden after environment creation by setting the attributes directly.
+    """
+
+    tags = {'now'}
+
+    def __init__(self, environment):
+        """Jinja2 Extension constructor."""
+        super().__init__(environment)
+
+        environment.extend(
+            datetime_format='%a, %d %b %Y %H:%M:%S',
+            default_timezone=os.getenv('TZ', 'UTC').strip()
+        )
+
+    def _datetime(self, timezone, operator, offset, datetime_format):
+        """
+        Get current datetime with time offset applied.
+
+        Args:
+            timezone: IANA timezone identifier (e.g., 'UTC', 'America/New_York') or empty string for default
+            operator: '+' for addition or '-' for subtraction
+            offset: Comma-separated offset parameters (e.g., 'hours=2,minutes=30')
+            datetime_format: strftime format string or None to use environment default
+
+        Returns:
+            Formatted datetime string with offset applied
+
+        Example:
+            _datetime('UTC', '+', 'hours=2,minutes=30', '%Y-%m-%d %H:%M:%S')
+            # Returns current time + 2.5 hours
+        """
+        # Use default timezone if none specified
+        if not timezone or timezone == '':
+            timezone = self.environment.default_timezone
+
+        d = arrow.now(timezone)
+
+        # parse shift params from offset and include operator
+        shift_params = {}
+        for param in offset.split(','):
+            interval, value = param.split('=')
+            shift_params[interval.strip()] = float(operator + value.strip())
+
+        # Fix weekday parameter can not be float
+        if 'weekday' in shift_params:
+            shift_params['weekday'] = int(shift_params['weekday'])
+
+        d = d.shift(**shift_params)
+
+        if datetime_format is None:
+            datetime_format = self.environment.datetime_format
+        return d.strftime(datetime_format)
+
+    def _now(self, timezone, datetime_format):
+        """
+        Get current datetime without any offset.
+
+        Args:
+            timezone: IANA timezone identifier (e.g., 'UTC', 'America/New_York') or empty string for default
+            datetime_format: strftime format string or None to use environment default
+
+        Returns:
+            Formatted datetime string for current time
+
+        Example:
+            _now('America/New_York', '%Y-%m-%d %H:%M:%S')
+            # Returns current time in New York timezone
+        """
+        # Use default timezone if none specified
+        if not timezone or timezone == '':
+            timezone = self.environment.default_timezone
+
+        if datetime_format is None:
+            datetime_format = self.environment.datetime_format
+        return arrow.now(timezone).strftime(datetime_format)
+
+    def parse(self, parser):
+        """
+        Parse the {% now %} tag and generate appropriate AST nodes.
+
+        This method is called by Jinja2 when it encounters a {% now %} tag.
+        It parses the tag syntax and determines whether to call _now() or _datetime()
+        based on whether offset operations (+ or -) are present.
+
+        Supported syntax:
+            {% now 'timezone' %}                              -> calls _now()
+            {% now 'timezone', 'format' %}                    -> calls _now()
+            {% now 'timezone' + 'offset' %}                   -> calls _datetime()
+            {% now 'timezone' + 'offset', 'format' %}         -> calls _datetime()
+            {% now 'timezone' - 'offset', 'format' %}         -> calls _datetime()
+
+        Args:
+            parser: Jinja2 parser instance
+
+        Returns:
+            nodes.Output: AST output node containing the formatted datetime string
+        """
+        lineno = next(parser.stream).lineno
+
+        node = parser.parse_expression()
+
+        if parser.stream.skip_if('comma'):
+            datetime_format = parser.parse_expression()
+        else:
+            datetime_format = nodes.Const(None)
+
+        if isinstance(node, nodes.Add):
+            call_method = self.call_method(
+                '_datetime',
+                [node.left, nodes.Const('+'), node.right, datetime_format],
+                lineno=lineno,
+            )
+        elif isinstance(node, nodes.Sub):
+            call_method = self.call_method(
+                '_datetime',
+                [node.left, nodes.Const('-'), node.right, datetime_format],
+                lineno=lineno,
+            )
+        else:
+            call_method = self.call_method(
+                '_now',
+                [node, datetime_format],
+                lineno=lineno,
+            )
+        return nodes.Output([call_method], lineno=lineno)

changedetectionio/jinja2_custom/safe_jinja.py

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+"""
+Safe Jinja2 render with max payload sizes
+
+See https://jinja.palletsprojects.com/en/3.1.x/sandbox/#security-considerations
+"""
+
+import jinja2.sandbox
+import typing as t
+import os
+from .extensions.TimeExtension import TimeExtension
+
+JINJA2_MAX_RETURN_PAYLOAD_SIZE = 1024 * int(os.getenv("JINJA2_MAX_RETURN_PAYLOAD_SIZE_KB", 1024 * 10))
+
+# Default extensions - can be overridden in create_jinja_env()
+DEFAULT_JINJA2_EXTENSIONS = [TimeExtension]
+
+
+def create_jinja_env(extensions=None, **kwargs) -> jinja2.sandbox.ImmutableSandboxedEnvironment:
+    """
+    Create a sandboxed Jinja2 environment with our custom extensions and default timezone.
+
+    Args:
+        extensions: List of extension classes to use (defaults to DEFAULT_JINJA2_EXTENSIONS)
+        **kwargs: Additional arguments to pass to ImmutableSandboxedEnvironment
+
+    Returns:
+        Configured Jinja2 environment
+    """
+    if extensions is None:
+        extensions = DEFAULT_JINJA2_EXTENSIONS
+
+    jinja2_env = jinja2.sandbox.ImmutableSandboxedEnvironment(
+        extensions=extensions,
+        **kwargs
+    )
+
+    # Get default timezone from environment variable
+    default_timezone = os.getenv('TZ', 'UTC').strip()
+    jinja2_env.default_timezone = default_timezone
+
+    return jinja2_env
+
+
+# This is used for notifications etc, so actually it's OK to send custom HTML such as <a href> etc, but it should limit what data is available.
+# (Which also limits available functions that could be called)
+def render(template_str, **args: t.Any) -> str:
+    jinja2_env = create_jinja_env()
+    output = jinja2_env.from_string(template_str).render(args)
+    return output[:JINJA2_MAX_RETURN_PAYLOAD_SIZE]
+
+def render_fully_escaped(content):
+    env = jinja2.sandbox.ImmutableSandboxedEnvironment(autoescape=True)
+    template = env.from_string("{{ some_html|e }}")
+    return template.render(some_html=content)
+