PME2: Action.context implementation for operator context override

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Summary

Design and implement the Action.context field for operator context override.

Background

JSON Schema v2 includes a context field for type: "command":

{
  "type": "command",
  "value": "bpy.ops.mesh.primitive_cube_add()",
  "context": "{'area': next(a for a in C.screen.areas if a.type == 'VIEW_3D')}"
}

Purpose

In Blender 4.x+, operator context override requires with syntax:

# Blender 4.x style
with context.temp_override(**override_dict):
    bpy.ops.some_operator()

The context field allows users to specify this override as a Python expression.

Implementation Plan

TBD - Detailed implementation plan to be added.

Considerations

• How to safely evaluate the context expression
• Error handling for invalid expressions
• UI for editing context override
• Documentation and examples
• Backward compatibility with existing command strings

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Implementation Details (Gap Supplement)

Context Override in Blender 4.x+

# Blender 4.x requires temp_override
# Old style (deprecated):
# bpy.ops.mesh.primitive_cube_add(override_dict)

# New style (Blender 4.x+):
with bpy.context.temp_override(**override_dict):
    bpy.ops.mesh.primitive_cube_add()

---

Action.context Field Usage

{
  "type": "command",
  "value": "bpy.ops.mesh.primitive_cube_add()",
  "context": "{'area': next(a for a in C.screen.areas if a.type == 'VIEW_3D')}"
}

The context field contains a Python expression that evaluates to a dict.

---

Execution Flow

def execute_command_action(action: Action, globals: dict) -> None:
    """Execute a command action with optional context override."""

    # Evaluate context expression if present
    override_dict = {}
    if action.context:
        try:
            override_dict = eval(action.context, globals)
        except Exception as e:
            print(f"PME: Context evaluation error: {e}")
            # Continue without override

    # Execute command
    if override_dict:
        with bpy.context.temp_override(**override_dict):
            exec(action.value, globals)
    else:
        exec(action.value, globals)

---

Security Considerations

The context field is evaluated using eval(), same as other PME Python code.

Risk	Mitigation
Arbitrary code execution	Same as command field - user trusts their own code
Context object access	Sandboxed by Blender's Python environment
Cross-session persistence	JSON stored locally, not shared

Note: PME already uses eval() for commands, poll, custom layouts.
The context field doesn't introduce new security risks.

---

Integration with pme.execute()

# pme.py enhancement
def execute(cmd: str, context_override: Optional[str] = None) -> Any:
    """Execute Python code with optional context override.

    Args:
        cmd: Python code to execute
        context_override: Python expression evaluating to override dict
    """
    globals = pme.context.globals

    if context_override:
        override_dict = eval(context_override, globals)
        with bpy.context.temp_override(**override_dict):
            return exec(cmd, globals)
    else:
        return exec(cmd, globals)

---

UI for Editing

Approach	Description
Text field	Simple StringProperty for Python expression
Template buttons	Common overrides (VIEW_3D, IMAGE_EDITOR, etc.)
Syntax validation	Check expression compiles on blur

---

PropertyGroup Addition

# prefs/pmi_data.py - PMIData addition
class PMIData(PropertyGroup):
    # NEW: Context override for command mode
    cmd_context: StringProperty(
        name="Context Override",
        description="Python expression for context.temp_override()",
        default="",
        maxlen=1024,
    )

---

See also: _docs/design/issue_gap_supplements.md

[Pluglug]

Recommend moving out of 2.0.0 scope.

This is a new feature that requires careful design. The schema field is defined, but implementation can be deferred to 2.0.1+.

For 2.0.0, commands will work without context override (existing behavior).