Add opt-in per-instrument logger scope (default_logger_scope)

[ymampaey]

Closes #8522

Summary

Every instrument currently shares one logging.Logger object because
InstrumentBase.__init__ uses the module name
qcodes.instrument.instrument_base. VISA communication similarly uses the
shared qcodes.instrument.instrument_base.com.visa logger.

This PR lets a driver opt in to module-qualified scoped loggers:

class MyDriver(VisaInstrument):
    default_logger_scope = "instrument"

QCoDeS only selects the logger name. It does not set levels, attach handlers,
or change propagate; those remain application and driver policy.

The default behavior is unchanged. Drivers that do not opt in continue to
use:

qcodes.instrument.instrument_base
qcodes.instrument.instrument_base.com.visa

How logger names are selected

InstrumentBase._logger_name receives the existing shared logger name as a
required fallback:

def _logger_name(self, default: str, *branch: str) -> str:
    root = self.root_instrument
    if root._logger_scope != "instrument":
        return default
    cls = type(root)
    return ".".join((cls.__module__, cls.__qualname__, *branch, *self.name_parts))

Regular instrument logging calls _logger_name(__name__). VISA logging calls
_logger_name(VISA_LOGGER, "com", "visa").

For an unscoped driver, _logger_name immediately returns __name__ or
VISA_LOGGER, preserving the existing names. For a scoped driver, that
fallback is ignored and the name is assembled from:

1. The root driver class's module.
2. The root driver class's qualified name.
3. An optional branch such as com.visa.
4. The instrument's name_parts.

The scope is resolved and stored once when the root instrument is initialized.
All channels and later-added submodules read the stored value from
root_instrument, preventing a hierarchy from splitting if the class attribute
changes later.

Naming examples

QCoDeS driver

qcodes.instrument_drivers.tektronix.AWG5208.TektronixAWG5208
qcodes.instrument_drivers.tektronix.AWG5208.TektronixAWG5208.awg
qcodes.instrument_drivers.tektronix.AWG5208.TektronixAWG5208.awg.ChanA

Custom driver

For MyDriver defined in my_lab.drivers.my_driver:

my_lab.drivers.my_driver.MyDriver
my_lab.drivers.my_driver.MyDriver.custom_inst
my_lab.drivers.my_driver.MyDriver.custom_inst.channel_a

A driver defined directly in a notebook starts with __main__:

__main__.MyDriver.custom_inst

VISA driver

For AMIModel430 and an instrument named mag_x:

qcodes.instrument_drivers.american_magnetics.AMI430_visa.AMIModel430
qcodes.instrument_drivers.american_magnetics.AMI430_visa.AMIModel430.mag_x
qcodes.instrument_drivers.american_magnetics.AMI430_visa.AMIModel430.com.visa
qcodes.instrument_drivers.american_magnetics.AMI430_visa.AMIModel430.com.visa.mag_x

The class logger is an ancestor of both the regular instrument branch and the
com.visa branch. Setting the class logger level therefore covers both driver
messages and wire traffic:

"logger_levels": {
  "qcodes.instrument_drivers.american_magnetics.AMI430_visa.AMIModel430": "DEBUG"
}

Design notes

Why module plus qualified class name. A class name alone is not unique.
Drivers with the same class name in different modules now receive distinct
logger trees.

Why the class comes from root_instrument. Using type(self) would put a
channel under its channel class rather than its instrument class. Using the
root class keeps channels below their instrument logger.

Why name_parts rather than full_name. Joining individual name parts
with . makes a channel logger a real descendant of its instrument logger.

Why VISA uses com.visa. It keeps driver messages and wire traffic
separately configurable while allowing the module-qualified driver class logger
to control both branches.

Documented caveats

• A per-instrument level such as ...AMIModel430.mag_x does not reach
  ...AMIModel430.com.visa.mag_x; set the class level or configure both.
• An instrument named com becomes an ancestor of the com.visa branch.
• Scoped drivers leave the qcodes.instrument.instrument_base hierarchy and
  therefore no longer inherit levels configured there.
• External and notebook drivers may start outside qcodes, for example
  qcodes_contrib_drivers or __main__.
• Classes defined inside functions include <locals> in __qualname__.
• Python's logging registry retains one entry per distinct instrument name.
• Module-qualified logger names can be long in the %(name)s output field.

Changes

File	Change
src/qcodes/instrument/instrument_base.py	Root-resolved scope and module-qualified scoped logger names
src/qcodes/instrument/visa.py, ip_to_visa.py	Dedicated scoped com.visa branch
tests/test_logger.py	Regression, hierarchy, collision, filtering, level, VISA, and IP-to-VISA coverage
docs/examples/logging/logging_example.ipynb	Updated examples, configuration, and caveats
docs/changes/newsfragments/8523.new	Updated feature description

Validation

• .venv\Scripts\python.exe -m pytest tests\test_logger.py — 33 passed.
• .venv\Scripts\python.exe -m pytest tests --reruns 1 — 3255 passed,
  268 skipped.
• .venv\Scripts\pyright.exe --pythonpath .venv\Scripts\python.exe — 0 errors,
  0 warnings.
• pre-commit run --all — all hooks passed.
• docs/examples/logging/logging_example.ipynb — executed successfully end to
  end.

[Copilot]

Copilot review overview

🟡 Changes recommended

Logger identity collisions and mutable scope resolution can break the promised isolation and hierarchy.

Get a fresh assessment by requesting another Copilot review.

Review effort: Balanced
Findings: 1 · 2 · 2

Open (5)

• Use module-qualified identities for per-driver logger isolation · New
• Store scope at root initialization for all descendants · New
• Avoid ambient logging levels in class logger test · New
• Clarify propagate=False and separate VISA logger behavior · New
• Document permanent logging-registry growth caveat · New

What changed in this PR

Adds opt-in per-instrument logger hierarchies while preserving shared logging by default.

Changes:

• Adds configurable logger scope and hierarchical names.
• Applies scoped naming to VISA loggers.
• Adds tests, documentation, and a newsfragment.

File	Description
instrument_base.py	Defines logger scopes and scoped-name generation.
visa.py	Applies scoped VISA logging.
ip_to_visa.py	Applies scoped logging to simulated VISA instruments.
test_logger.py	Tests scope, inheritance, filtering, and VISA behavior.
logging_example.ipynb	Documents scoped logger usage.
8523.new	Announces the feature.

---

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 72.32%. Comparing base (f6b9dd6) to head (e479ab4).
⚠️ Report is 141 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
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+ Coverage   72.00%   72.32%   +0.32%     
==========================================
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==========================================
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+ Misses       8964     8948      -16     

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