Cross File Source Of Truth Grep

Cross-File Source-of-Truth Grep

✅ PROMOTED — TDD Cycle 1 PASS. RED subagent gave a heuristic "grep first" recommendation, but without the decisive 4th grep pass on mapping values. GREEN subagent added the 4th pass grep -rn "'CL=F'\s*:\s*'WTI" — which catches copies of the mapping structure under deviating variable names (_DISPLAY_MAP, LABELS, dicts embedded inside helper functions). Precisely this pass would have caught the signal_dispatcher.py:_get_display_name bug before the refactor. R1 refactor applied: 4th grep pass in Quick Reference as a separate line + hint block.

Overview

Before every refactor: grep -r for the OLD pattern, not the NEW one.

When you replace an old pattern (column name, helper call, inline dict, default string, deprecated import) with a new one, 2-5 additional callers often lurk that you didn't have in the mental model of "the 3 relevant files":

• notifications/ dispatcher (Telegram, email, webhook)
• Scheduler jobs (cron-triggered, often rarely touched)
• Batch scripts (offline analytics)
• Integration tests + mock fixtures
• Deprecated-but-still-in-path modules

Skill = simple discipline: grep -rn "<old-pattern>" BEFORE you write the first new call. 30 seconds of effort prevents hours of re-review cycle.

This maxim is the refactor-variant of the "Single Source of Truth" maxim: the SoT migration is only complete when grep for the old pattern returns nothing.

When to use

Trigger phrases (the kind you'd be about to use):

• "I'm refactoring to "
• "fix schema drift in ."
• "introduce SoT for <Display-Name / config-var / helper>"
• "migrate from old config_loader path to new"
• "rename helper-function from foo to bar"
• "deprecated import cleanup"
• "extract config defaults from code"

High-risk markers (additional trigger):

• You have a small list of affected files in mind (≤5) — precisely then grep, because that's the case most prone to under-estimation
• The new pattern already lives somewhere ("we standardized this in core/") — meaning older spots are not migrated yet
• Module belongs to notification / dispatcher / scheduler / cron / batch — these paths are rarely touched, drift accumulates

When NOT to use

• Greenfield code: the old pattern doesn't exist yet
• Pure cosmetic rename in a single file: local variable, no semantic shift
• Guaranteed file-local helper: _private_helper in module, with _ prefix convention
• Rename of a symbol with IDE refactor-tool: when LSP refactor cleanly covers all callers, grep is redundant (but verify 1× afterwards anyway)

The 4-Step Cross-File SoT Grep Flow

Step 1 — Note the old pattern explicitly

Before grep, write as a comment or via TodoWrite:

• Old pattern: o.yf_symbol (column alias)
• New pattern: o.symbol AS yf_symbol
• Suspected caller count: 3 (signals.py, timeline.py, take_signal)
• What I expect to find: 3-5 (with ~2 extra in tests/mocks)

Step 2 — Grep with repo scope

# Standard: all Python files incl. tests, scripts, integrations
grep -rn "<old-pattern>" --include="*.py" \
  --exclude-dir=node_modules \
  --exclude-dir=.git \
  --exclude-dir=__pycache__ \
  --exclude-dir=.venv \
  | grep -v "\.pyc:"

Never just in a subdirectory (grep ... /core/). That misses the skill's goal.

Step 3 — Categorize the hit list

Sort each hit into one of these categories:

Step 4 — Migrate + verification grep

After the refactor: grep again grep -rn "<old-pattern>" — result should be empty (or only the doc/comment false-positives remain).

grep -rn "<old-pattern>" --include="*.py" | wc -l
# Expectation: 0 (or list of deliberately not-migrated hits)

Quick Reference

R1 refactor (Cycle 1): the substring-grep on mapping values ('CL=F': 'WTI) is the most critical variant — it finds copies of the mapping structure under deviating variable names. Precisely this variant would have caught the signal_dispatcher.py:_get_display_name bug BEFORE the refactor (the dict there was not named display_names but was embedded in a helper function).

Anti-Patterns

Cost of Skipping (real)

Experience from a Phase-1 re-review (code-review cleanup):

• Display-name SoT migration to core/utils/display.instrument_label() had covered 4 hot-path files
• Re-review subagent found notifications/signal_dispatcher.py:_get_display_name with old config_loader path
• Would have stayed unnoticed for weeks in the V1/V2 signal Telegram dispatch — symbols in Telegram instead of display names

Pattern: notification-dispatcher modules are rarely touched + often have their own helper versions that are not visible in the main refactor path.

Lesson: 30s grep upfront = hours of re-review cycle saved.

Red Flags — STOP and grep

• You're writing the first new call after a refactor right now
• Your mental model is "the 3 files" or "only in /core/"
• Notification/scheduler/batch were not explicitly mentioned in your list
• LSP refactor ran cleanly, but you have dynamic imports in the codebase

All mean: 30s repo-wide grep on old pattern, then categorize hit list, then migrate.

Cross-References

• REQUIRED COMPLEMENT: pre-deploy-code-drift-detection (drift check AFTER the refactor)
• COMPLEMENT: silent-except-hides-schema-drift (same bug class from the symptom side)
• Maxim: "Single Source of Truth — hardcoded defaults are ticking time bombs"

Background: TDD progression (Bulletproofing log)

Cycle 1 — PASS with R1 refactor

• RED subagent (without skill, scenario "migrate display_names inline-dicts to central instrument_label(), 3 known files"): heuristically recommended "first grep for further occurrences" — surprisingly good, but only the variable-name grep (grep -rn "display_names"). Self-critique listed 7 points (repo not inspected, DB as SoT not addressed, migration order with imports, tests before deletion, tooling hint, anti-pattern arc, no dict diff before merge).

• GREEN subagent (with skill): brought the decisive added value — the 4th grep pass on mapping values (grep -rn "'CL=F'\s*:\s*'WTI") that catches copies of the mapping structure under deviating variable names. Plus: named concrete high-risk paths for the codebase (notifications/signal_dispatcher.py, notifications/telegram_*.py, scheduler/jobs/*.py, briefings/*.py), cross-reference to pre-deploy-code-drift-detection as complement after the refactor, schema-use-case-mismatch hint (display_name IS NULL check).

• R1 refactor applied: Quick Reference table extended with row "Inline-dict → SoT (value substring, catches obscured names)" + hint block that this is the most critical variant (would have caught the bug).

• Anti-pattern avoided: GREEN predicted the bug exactly — notifications/signal_dispatcher.py with its own _get_display_name would have stayed unmigrated, raw symbols in the V1/V2 Telegram dispatch for weeks.

Cycle-2-Backlog (Polish, non-blocking)

1. CWD hint for subagent use-cases: "when your CWD is not the target repo: first cd or delegate commands to user". GREEN subagent had a CWD mismatch (vault instead of repo) and had to solve that via command suggestions.
2. LSP find_references as complement source (not only as anti-pattern): for LSP-capable repos additional verification alongside grep.
3. Schema-use-case mismatch as explicit sub-check in Step 3: for DB-backed lookups (instruments.display_name IS NULL) a DB-data-state check before migration is needed — own drift class.
4. High-risk paths list for the codebase as Quick Reference: notification/, scheduler/, briefings/, analytics/, tests/integration/ — project-specifically valuable.