118: fix factor label collision in robin_surv()

[danielinteractive]

closes #118

• Added regression tests for user facing bugs
• Added generic h_joint_strata()
• Updated both affected grouping sites in R/survival_score.R
• Randomization-strata nesting checks
• Stratified score and variance calculation
• Added helper tests covering:
  • 200 randomized equivalence cases against interaction().
  • Colliding labels remaining distinct via level-code identity.
• Added a bug-fix entry to NEWS.md

[github-actions]

Code Coverage Summary

Filename                     Stmts    Miss  Cover    Missing
-------------------------  -------  ------  -------  -------------
R/bias.R                        34       0  100.00%
R/find_data.R                    3       0  100.00%
R/predict_couterfactual.R       77       0  100.00%
R/prediction_cf.R               22       0  100.00%
R/robin_glm.R                   49       1  97.96%   40
R/robin_lm.R                    28       0  100.00%
R/surv_effect.R                 67       0  100.00%
R/survival_cov_adj.R           146       0  100.00%
R/survival_score.R             293       0  100.00%
R/survival.R                   345       0  100.00%
R/treatment_effect.R           101       1  99.01%   53
R/utils.R                      218       3  98.62%   121, 153, 157
R/variance_anhecova.R           44       0  100.00%
R/variance_hc.R                 10       0  100.00%
TOTAL                         1437       5  99.65%

Diff against main

Filename              Stmts    Miss  Cover
------------------  -------  ------  --------
R/survival_score.R       -1       0  +100.00%
R/survival.R              0      -1  +0.29%
R/utils.R               +14       0  +0.09%
TOTAL                   +13      -1  +0.07%

Results for commit: d749e31

Minimum allowed coverage is 80%

♻️ This comment has been updated with latest results

[github-actions]

Unit Tests Summary

  1 files   13 suites   13s ⏱️
148 tests 102 ✅ 46 💤 0 ❌
376 runs  312 ✅ 64 💤 0 ❌

Results for commit d749e31.

♻️ This comment has been updated with latest results.

[github-actions]

Unit Test Performance Difference

Additional test case details

Test Suite	$Status$	Time on main	$±Time$	Test Case
survival	👶		$+0.17$	robin_surv_gives_the_same_result_for_strata_when_the_labels_differ
survival	👶		$+0.05$	robin_surv_gives_warning_also_with_special_strata_labels
survival	👶		$+0.06$	robin_surv_works_as_expected_when_some_strata_are_NA
utils	👶		$+0.01$	h_joint_strata_derives_identity_from_level_codes
utils	👶		$+0.01$	h_joint_strata_fails_when_there_are_missing_values
utils	👶		$+0.09$	h_joint_strata_matches_interaction_when_labels_do_not_collide

Results for commit e1fea34

♻️ This comment has been updated with latest results.

[clarkliming]

review in progress and take some time, please forgive me cause busy with work these days

[danielinteractive]

@clarkliming I am merging this now (after AI review), otherwise it is difficult to work on the next issue that also is about robin_surv. I think the risk is reasonably low here. We can always revisit the details if you find something later. Thanks!

[Copilot]

Copilot review overview

🟡 Changes recommended

h_joint_strata() currently errors on NA inputs (regression vs interaction()), and data-raw/create_glm_data.R has a pipeline syntax error plus uses |> despite the package declaring R (>= 3.6).

Get a fresh assessment by requesting another Copilot review.

Review effort: Lite
Findings: 1 · 1

Open (2)

• Syntax error and incompatible base pipe usage · New
• NA strata values crash h_joint_strata() · New

What changed in this PR

This PR addresses #118 by preventing robin_surv() from collapsing distinct joint strata when factor labels collide (e.g., "a.b" + "c" vs "a" + "b.c"), by introducing a code-based joint-strata helper and using it in the stratified survival score logic.

Changes:

• Added h_joint_strata() to build joint strata based on factor level codes (not pasted labels) and applied it in R/survival_score.R for both nesting checks and stratified splitting.
• Added regression tests covering label-renaming invariance and warning behavior with “special” (collision-prone) labels, plus helper-level tests for equivalence to interaction() when safe.
• Miscellaneous maintenance/formatting updates (implicit return, seq_along(), argument formatting, NEWS entry, and a data-raw script refactor).

File	Description
vignettes/​articles/​robincar-validate.Rmd	Small boolean operator tweak inside validation vignette code.
tests/​testthat/​test-utils.R	Adds unit tests for h_joint_strata() behavior and collision handling.
tests/​testthat/​test-survival.R	Adds regression tests for the strata-collision bug and warning behavior.
R/​variance_anhecova.R	Minor internal cleanup (seq_along(), implicit return).
R/​utils.R	Introduces h_joint_strata() helper (core of the fix).
R/​treatment_effect.R	Formatting/indentation changes only.
R/​survival_score.R	Replaces label-based interaction()/split() usage with h_joint_strata() at both affected sites.
NEWS.md	Adds a bug-fix entry for the strata-collision issue.
man/​h_joint_strata.Rd	Generated documentation for the new internal helper.
data-raw/​create_glm_data.R	Refactors pipeline syntax in data generation script.

Files not reviewed (1)

• man/h_joint_strata.Rd: Generated file

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