Let a printer driver carry the name Windows actually matches on

The driver form and the API both dropped `drivername` and `vendorid`. POST
returned 201 with both null, PUT accepted them and stored nothing, and no
screen offered either field - so there was no interface in the product that
could set them.

That is not a cosmetic gap. `drivername` is the exact string the INF declares,
and Add-PrinterDriver matches on it; `name` is ours to choose and means nothing
to Windows. With it null the shipped converger has nothing to match and
installs nothing, and the drift check that compares an observed driver name
against the expected one could never fire, because the expected value was never
stored. `vendorid` is how a universal driver (HP UPD, Xerox GPD) attaches to a
whole make instead of needing a near-duplicate row per model.

Both are now read on create and update, and the driver form gained the two
fields with hints saying what they are for - the INF name box says plainly that
leaving it blank means the converger cannot install that driver. A whitespace
value clears rather than stores: an empty box means "not known", and a blank
string would look set and match nothing.

Three tests. Verified by planting: drop the two fields from the create path
again and the round-trip test fails.

Scope: product

tests/test_plugins/test_printer_driver_resolution.py

@@ -118,3 +118,60 @@ def test_a_row_that_names_a_vendor_is_not_matched_by_its_text(db, fleet):
     printer = Printer(vendorid=brother.vendorid, modelnumberid=None)
     printer.vendor = brother
     assert _printer_driver(printer, _universal()) is None
+
+
+# --- the two fields the converger actually needs -----------------------------
+#
+# drivername is the exact string the INF declares, and it is what
+# Add-PrinterDriver matches on - `name` is ours to choose and means nothing to
+# Windows. vendorid attaches a universal driver (HP UPD, Xerox GPD) to a whole
+# make. Neither was read from the request body, so both came back null on a
+# 201, and there was no interface that could set them: the shipped converger
+# had nothing to match and installed nothing, and driver-name drift could never
+# be detected because the expected value was never stored.
+
+def test_a_driver_keeps_the_inf_name_and_vendor_it_was_given(client, db,
+                                                             auth_headers):
+    from plugins.printers.models import PrinterDriver
+
+    created = client.post('/api/printers/drivers', headers=auth_headers, json={
+        'name': 'HP universal',
+        'location': r'\\server\share\hpupd',
+        'drivername': 'HP Universal Printing PCL 6',
+        'vendorid': 1,
+    })
+    assert created.status_code == 201, created.get_json()
+    body = created.get_json()['data']
+    assert body['drivername'] == 'HP Universal Printing PCL 6'
+    assert body['vendorid'] == 1
+
+    stored = db.session.get(PrinterDriver, body['driverid'])
+    assert stored.drivername == 'HP Universal Printing PCL 6'
+    assert stored.vendorid == 1
+
+
+def test_the_inf_name_and_vendor_can_be_changed_afterwards(client, db,
+                                                           auth_headers):
+    created = client.post('/api/printers/drivers', headers=auth_headers, json={
+        'name': 'Xerox universal', 'location': r'\\server\share\xerox'})
+    driverid = created.get_json()['data']['driverid']
+    assert created.get_json()['data']['drivername'] is None
+
+    updated = client.put('/api/printers/drivers/%d' % driverid,
+                         headers=auth_headers,
+                         json={'drivername': 'Xerox Global Print Driver PCL6',
+                               'vendorid': 2})
+    assert updated.status_code == 200, updated.get_json()
+    assert updated.get_json()['data']['drivername'] == \
+        'Xerox Global Print Driver PCL6'
+    assert updated.get_json()['data']['vendorid'] == 2
+
+
+def test_a_blank_inf_name_clears_it_rather_than_storing_whitespace(
+        client, db, auth_headers):
+    """An empty box means "not known", which the converger reads as "cannot
+    install this". A whitespace string would look set and match nothing."""
+    created = client.post('/api/printers/drivers', headers=auth_headers, json={
+        'name': 'Blank test', 'location': r'\\server\share\blank',
+        'drivername': '   '})
+    assert created.get_json()['data']['drivername'] is None