Deduplicate ExperimentConfig/read_config; move initial_condition to common

[jcanton]

from a friend:

Closes #1320

What

ExperimentConfig and the Fortran-namelist config reader were duplicated between standalone_driver and testing, each carrying a # NOTE: duplicate ... to avoid circular imports marker. The duplication existed because testing depended on standalone_driver (for DriverConfig/InitialConditionConfig) — the wrong direction, since the standalone driver should sit at the top of the dependency graph with nothing depending on it.

Changes

• New icon4py.model.experiment_config package holding the single ExperimentConfig, DriverConfig, and the shared read_experiment_config reader. It sits above the atmosphere packages but below both testing and standalone_driver, so neither depends on the other — the testing -> standalone_driver edge is gone.
• standalone_driver.config.read_config and testing.datatest_utils.create_experiment_configuration are now thin wrappers over the shared reader.
• Moved the initial_condition subpackage to common/initial_condition/, mirroring common/topography/, so the IC config dataclasses stay next to their compute functions. This required relocating StaticFieldFactories (a NamedTuple of common factories) to common/states/static_fields.py.
• Dropped the now-unused serialbox4py dependency from standalone_driver (its only user moved to common, which already depends on it).
• Removed the now-resolved # type: ignore[arg-type] / TODO(1320) workarounds in the standalone-driver initial-condition tests, since both sides now share a single ExperimentConfig type.

[jcanton]

@DropD I thought of getting this one in before it risks becoming annoying for your config PRs, hopefully it doesn't annoy you now, but if so we can postpone it to a later time

[github-actions]

Mandatory Tests

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Available options are:

• SESSIONS: model, model_mpi, or tools (correspond to nox sessions)
• MODEL_SUBSETS: datatest, basic, or stencils (correspond to nox session selections)
• MODEL_SUBPACKAGES: subpackages for non-MPI tests (last component, e.g. diffusion, standalone_driver)
• MODEL_MPI_SUBPACKAGES: subpackages for MPI tests (as above)
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• GRIDS: grids for stencil tests (simple, icon_regional, or icon_global)
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[jcanton]

cscs-ci run default;BACKENDS=gtfn_cpu;LEVELS=unit:integration

[Copilot]

Pull request overview

This PR removes duplicated experiment-configuration code by introducing a shared icon4py.model.experiment_config package, and relocates initial-condition functionality into icon4py.model.common to fix an inverted dependency (testing -> standalone_driver) in the monorepo.

Changes:

• Add model/experiment_config with the canonical ExperimentConfig/DriverConfig and a shared read_experiment_config(...) reader; update tach.toml, workspace deps, and mypy paths accordingly.
• Replace duplicated readers in standalone_driver.config.read_config and testing.datatest_utils.create_experiment_configuration with thin wrappers over the shared reader.
• Move initial-condition code (and StaticFieldFactories) into icon4py.model.common, and update standalone-driver code/tests to import from the new locations.

Reviewed changes

Copilot reviewed 21 out of 26 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
uv.lock	Adds workspace member + dependency for icon4py-experiment-config; removes standalone-driver’s direct serialbox4py dep.
tach.toml	Adds icon4py.model.experiment_config module + adjusts dependency edges for testing and standalone_driver.
pyproject.toml	Registers new workspace member, dependency, and mypy/pytest paths; updates mypy override for moved IC package.
model/testing/src/icon4py/model/testing/definitions.py	Removes duplicated ExperimentConfig and imports the shared one.
model/testing/src/icon4py/model/testing/datatest_utils.py	Replaces local config assembly with read_experiment_config(...).
model/standalone_driver/tests/standalone_driver/mpi_tests/test_parallel_initial_conditions.py	Updates IC imports and removes now-unneeded type-ignore/TODO.
model/standalone_driver/tests/standalone_driver/integration_tests/test_initial_conditions.py	Updates IC imports and removes now-unneeded type-ignore/TODO.
model/standalone_driver/src/icon4py/model/standalone_driver/standalone_driver.py	Switches IC imports to icon4py.model.common.initial_condition.
model/standalone_driver/src/icon4py/model/standalone_driver/driver_states.py	Moves StaticFieldFactories to common and imports it from there.
model/standalone_driver/src/icon4py/model/standalone_driver/config.py	Re-exports shared config types and delegates read_config(...) to shared reader.
model/standalone_driver/pyproject.toml	Drops direct serialbox4py dependency.
model/experiment_config/src/icon4py/model/experiment_config/reader.py	New shared Fortran-namelist config reader assembling ExperimentConfig.
model/experiment_config/src/icon4py/model/experiment_config/config.py	New shared config dataclasses and type aliases for experiments/driver.
model/experiment_config/src/icon4py/model/experiment_config/init.py	New package metadata/version module.
model/experiment_config/src/icon4py/model/experiment_config/py.typed	Marks package as typed.
model/experiment_config/README.md	New package documentation.
model/experiment_config/pyproject.toml	New package build metadata and dependencies.
model/common/src/icon4py/model/common/topography/from_file.py	Updates documentation reference due to IC move.
model/common/src/icon4py/model/common/states/static_fields.py	New home for StaticFieldFactories.
model/common/src/icon4py/model/common/initial_condition/from_file.py	New file-based initial-condition implementation under common.
model/common/src/icon4py/model/common/initial_condition/config.py	Updates IC config + dispatcher to use new common IC subpackage layout.
model/common/src/icon4py/model/common/initial_condition/analytical/utils.py	Adds shared analytical-IC helper utilities under common.
model/common/src/icon4py/model/common/initial_condition/analytical/jablonowski_williamson.py	Updates imports/types to use common IC utilities + StaticFieldFactories.
model/common/src/icon4py/model/common/initial_condition/analytical/gauss3d.py	Updates imports/types to use common IC utilities + StaticFieldFactories.
model/common/src/icon4py/model/common/initial_condition/analytical/init.py	Adds package init for analytical IC submodule.
model/common/src/icon4py/model/common/initial_condition/init.py	Re-exports InitialConditionConfig and create from the new common location.

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