Fix game.objective being overwritten by change_grammar() when quests exist

[Greg Sochanik (gregyoto)]

Summary

• Fixes game.objective still overwritten by change_grammar() when quests exist (regression of #239) #373 (regression of Prevent overwriting quest's description and game's objective. #239)
• In change_grammar(), only auto-generate the objective via describe_event() if self._objective is None, preventing it from overwriting a manually-set objective
• Adds a regression test that covers the case with quests (the existing test from PR Prevent text generation process from overwriting quest's description and game's objective. #240 only tested games without quests)

What was happening

PR #240 added code in build() to copy a manually-set _objective from a previous build (line 788-789 of maker.py). However, change_grammar() is called after this copy (line 803), and it unconditionally overwrites the objective:

# game.py line 460 (before this fix)
self.objective = describe_event(Event(policy), self, self.grammar)

This means the preserved objective gets clobbered whenever the game has quests with a winning policy (i.e. most games).

The fix

One line change in game.py:

# Only auto-generate if no objective has been set
if self._objective is None:
    self.objective = describe_event(Event(policy), self, self.grammar)

Test plan

• New test test_manually_defined_objective_with_quests verifies that a manually-set objective survives build() and compile() when the game has quests
• Existing test test_manually_defined_objective continues to pass (games without quests)
• Normal games without a custom objective still get auto-generated objective text as before

Made with Cursor

[Greg Sochanik (gregyoto)]

@microsoft-github-policy-service agree

[Marc-Alexandre Côté (MarcCote)]

Great catch. Thanks for the PR. You can ignore the PEP8 error, I have fixed it in an upcoming PR (#372).

[Copilot]

Copilot review overview

🟡 Changes recommended

The guard prevents objectives from regenerating when callers subsequently change grammar.

Review effort: Balanced
Findings: 1

Open (1)

• Preserve generated objective when changing grammar · New

What changed in this PR

Prevents manually assigned objectives from being overwritten during GameMaker compilation.

Changes:

• Guards automatic objective generation.
• Adds a quest-based regression test.

File	Description
textworld/​generator/​game.py	Conditionally generates objectives.
textworld/​generator/​tests/​test_maker.py	Tests custom objective preservation.

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