# Anti-Patterns

> ⚠️ **NOTE**: Section 1 below was **investigated and resolved** — it is NOT a bug (see §1 for details).

---

## 1. ~~CRITICAL: Entity-ID / Party-Name Mismatch in `compute_party_coords`~~ → **INVALID — INVESTIGATED & RESOLVED**

**Investigation Date**: 2026-03-31

**Investigation Summary**: After thorough analysis of the database schema and code, this anti-pattern is **INVALID**. The original concern was based on a false assumption about `svd_vectors.entity_id` containing party names.

**Investigation Findings**:
1. **`svd_vectors` table has NO rows with `entity_type='party'`** — only `mp` and `motion` entity types exist in practice.
2. **`entity_ids in svd_vectors are always MP names** (e.g., `"Van Dijk, I."`), never party names. The party centroids are correctly computed via `mp_metadata` lookups.
3. **The trajectories plot WORKS correctly** — no production bug exists. The code path for party-level visualization does not rely on `svd_vectors.entity_id` containing party names.

**Conclusion**: The original anti-pattern was a false positive caused by incorrect assumptions about data contents. The `party_map` reverse-lookup (`mp_name → party_name`) works correctly because `entity_id` values are always MP names, not party names.

---

## 2. Bare `except: pass`

**File**: `database.py`, line 47

**Problem**: Catches **all** exceptions including `KeyboardInterrupt`, `SystemExit`, `MemoryError`.
Silently swallows errors — no logging, no fallback.

**Broken code**:
```python
try:
    self.conn.execute(sql)
except:  # ← bare except
    pass
```

**Fix**:
```python
try:
    self.conn.execute(sql)
except ibis.errors.IbisError as e:
    st.warning(f"Query failed: {e}")
    raise  # or return a default
```

---

## 3. Nested Exception Handling

**File**: `explorer.py`, lines 244–261

**Problem**: Try/except inside try/except creates opaque error paths. Inner exception silently swallows outer intent.

**Broken code**:
```python
try:
    result = compute_svd(motions)
    # ...
except Exception:
    try:
        # Try fallback approach
        result = fallback_compute(motions)
    except Exception:
        pass  # ← both exceptions silently dropped
```

**Fix**: Flatten — handle each case explicitly, or use a decorator.

---

## 4. Catch-All `Exception` Used Everywhere

**Problem**: `except Exception:` catches 50+ exception types including `ValueError`, `TypeError`, `KeyError`.
Overly broad — masks real bugs.

**Occurrence**: 850+ instances of bare/generic exception handlers across codebase.

**Fix**: Catch specific exceptions. If you must catch multiple, chain them:
```python
except (KeyError, ValueError) as e:
    logger.warning(f"Missing field: {e}")
```

---

## 5. No `entity_id` Format Validation

**Problem**: `svd_vectors.entity_id` can be either:
- An MP name (e.g., `"Van Dijk, I."`) for individual-level SVD
- A party name (e.g., `"GroenLinks-PvdA"`) for party-level SVD

No validation distinguishes which is which. Code must infer from context. (Note: In practice `svd_vectors.entity_id` only contains MP names — see §1 for investigation findings.)

**Fix**: Add explicit format marker or separate columns:
```python
# Option A: separate columns
svd_vectors = pd.DataFrame({
    'mp_name': [...],       # nullable
    'party_name': [...],     # nullable
    'window': [...],
    'vector_2d': [...]
})

# Option B: format prefix
# "mp:Van Dijk, I." or "party:GroenLinks-PvdA"
```

---

## 6. Silent Fallback When Party Centroids Fail

**Problem**: If `party_map` lookup fails (entity is a party, not MP), the code silently produces
`party_map_count: 0` and empty `parties_with_centroid_counts`. No warning is raised.

**Fix**: Add validation and warning:
```python
if party_map_count == 0:
    st.warning(f"No party mappings found for {len(svd_df)} entities in window '{window}'")
```

---

## 7. Three Separate Party Alias Dictionaries (No Single Source of Truth)

**Problem**: Party name variations exist in 3+ places:
- `PARTY_COLOURS` keys
- `party_map` values (from `mp_party_history`)
- Raw data column values

No canonical alias mapping. Spelling mismatches cause silent failures.

**Fix**: Create one `PARTY_ALIASES` dict in `config.py`:
```python
PARTY_ALIASES = {
    "GroenLinks-PvdA": ["GL-PvdA", "GroenLinks PvdA", "PvdA-GroenLinks"],
    "PVV": ["Partij voor de Vrijheid"],
    ...
}

def resolve_party(name: str) -> str:
    """Normalize any party name variant to canonical form."""
    for canonical, aliases in PARTY_ALIASES.items():
        if name in aliases or name == canonical:
            return canonical
    return name  # no alias found
```