Refuse an unregistered --symbols instead of reporting wrote=0

src/marketdata/update.py

@@ -143,6 +143,27 @@ def main(argv=None) -> int:
             p.error(f"{flag} modifies the databento ingest. Pass it with "
                     f"--ingest-databento.")
 
+    # Same rule once more, for --symbols. A symbol the registry does not carry
+    # cannot be fetched by anything, and the providers disagreed about what to do
+    # with one: databento refuses it (KeyError, "not in the marketdata registry"),
+    # while yfinance and norgate filtered it out and returned ok=True with wrote=0
+    # -- exit 0, a wrapper's `if not errorlevel 1` reading it as a good run. So
+    # `--symbols VIX` against a registry that no longer carries VIX reported
+    # SUCCESS while fetching nothing, and a symbol retired out of the registry
+    # took its consumers' fetches down silently, months from whoever did it. The
+    # check belongs here rather than in each provider: an unscoped `--bars` runs
+    # every domain, so a futures symbol legitimately resolves to nothing in
+    # yfinance and vice versa, and a per-provider refusal would fail a run the
+    # other half handled fine.
+    if args.symbols:
+        from .registry import REGISTRY
+        unknown = [s for s in args.symbols if s not in REGISTRY]
+        if unknown:
+            p.error("not in the marketdata registry: " + ", ".join(unknown)
+                    + ". Nothing would be fetched for these, so this is refused "
+                      "rather than reported as a run that wrote 0 rows. Check the "
+                      "spelling, or add them to registry.yaml.")
+
     if args.final_cutoff:
         print(f"note: --final-cutoff {args.final_cutoff} is deprecated and ignored. "
               f"The finals gate is data-driven (a newer settled bar than the store "

tests/test_cli_symbols.py

@@ -0,0 +1,62 @@
+"""`marketdata-update --symbols`: a symbol the registry does not carry must be
+refused, not filtered out.
+
+The providers used to disagree. databento raised KeyError on an unregistered
+symbol; yfinance and norgate dropped it from their target list and returned
+ok=True with wrote=0, which `main` turns into exit 0. So `--symbols VIX` against a
+registry that no longer carried VIX printed a line nobody reads and reported a
+successful run, and a wrapper testing `if not errorlevel 1` went on to sync a
+store nothing had been written to. That is the failure mode a retired symbol
+hands to its consumers, months after the retirement, looking like a typo.
+"""
+import pytest
+
+from marketdata import update
+from marketdata.providers import norgate as nprov
+from marketdata.providers import yfinance as yprov
+
+YF_OK = {"kind": "bars_yahoo", "ok": True, "wrote": 1, "failed": 0}
+NG_OK = {"kind": "bars_futures_norgate", "ok": True, "wrote": 1, "failed": 0,
+         "errors": [], "rows": 10, "newest": "2026-08-20"}
+
+
+def test_an_unregistered_symbol_is_refused(capsys):
+    with pytest.raises(SystemExit):
+        update.main(["--bars", "--symbols", "NOTASYMBOL"])
+    err = capsys.readouterr().err
+    assert "not in the marketdata registry" in err
+    assert "NOTASYMBOL" in err
+
+
+def test_refused_even_when_other_requested_symbols_are_valid(capsys):
+    """A partially satisfiable request is still not the request that was made. If
+    one of four symbols has been retired out of the registry, the run must say so
+    rather than quietly fetch three and exit 0."""
+    with pytest.raises(SystemExit):
+        update.main(["--bars", "--symbols", "SPY", "NOTASYMBOL"])
+    err = capsys.readouterr().err
+    assert "NOTASYMBOL" in err
+    assert "SPY" not in err          # names what is wrong, not what is fine
+
+
+def test_a_registered_symbol_is_not_refused(monkeypatch):
+    """The guard must not over-fire on the case it exists to protect."""
+    monkeypatch.setattr(yprov, "update", lambda *a, **k: YF_OK)
+    monkeypatch.setattr(nprov, "update", lambda *a, **k: NG_OK)
+    assert update.main(["--bars", "--domain", "equities", "--symbols", "VIX"]) == 0
+
+
+def test_an_equities_symbol_does_not_fail_the_futures_half(monkeypatch):
+    """An unscoped --bars runs every domain, so an equities symbol resolves to
+    nothing in norgate and a futures symbol resolves to nothing in yfinance. That
+    is why the check lives in main() and not in each provider: a per-provider
+    refusal would fail a run the other half handled perfectly well."""
+    monkeypatch.setattr(yprov, "update", lambda *a, **k: YF_OK)
+    monkeypatch.setattr(nprov, "update", lambda *a, **k: NG_OK)
+    assert update.main(["--bars", "--symbols", "VIX"]) == 0
+
+
+def test_no_symbols_means_no_check(monkeypatch):
+    monkeypatch.setattr(yprov, "update", lambda *a, **k: YF_OK)
+    monkeypatch.setattr(nprov, "update", lambda *a, **k: NG_OK)
+    assert update.main(["--bars", "--domain", "equities"]) == 0