Add parse and dispatch strategy

The current method of executing subcommands can be improved using a
"parse and dispatch" strategy. Whereby you don't need to run a
conditional to work out which subcommand to use.

This change refactors the Benchcab class so that its "public" methods
can be dispatched easily when inspecting the argparse.Namespace object
returned by the command line parser.

Fixes #196

benchcab/benchcab.py

@@ -1,15 +1,15 @@
 """Contains the main program entry point for `benchcab`."""
 
+import argparse
+import functools
 import grp
 import os
-import shutil
 import sys
 from pathlib import Path
 from subprocess import CalledProcessError
 from typing import Optional
 
 from benchcab import internal
-from benchcab.cli import generate_parser
 from benchcab.comparison import run_comparisons, run_comparisons_in_parallel
 from benchcab.config import read_config
 from benchcab.environment_modules import EnvironmentModules, EnvironmentModulesInterface
@@ -37,27 +37,19 @@ class Benchcab:
 
     def __init__(
         self,
-        argv: list[str],
         benchcab_exe_path: Optional[Path],
-        config: Optional[dict] = None,
         validate_env: bool = True,
     ) -> None:
-        self.args = generate_parser().parse_args(argv[1:] if argv[1:] else ["-h"])
-        self.config = config if config else read_config(Path(self.args.config))
-        self.repos = [
-            CableRepository(**config, repo_id=id)
-            for id, config in enumerate(self.config["realisations"])
-        ]
-        self.tasks: list[Task] = []  # initialise fluxsite tasks lazily
         self.benchcab_exe_path = benchcab_exe_path
+        self.validate_env = validate_env
 
-        if validate_env:
-            self._validate_environment(
-                project=self.config["project"], modules=self.config["modules"]
-            )
+        self.tasks: list[Task] = []  # initialise fluxsite tasks lazily
 
     def _validate_environment(self, project: str, modules: list):
         """Performs checks on current user environment."""
+        if not self.validate_env:
+            return
+
         if "gadi.nci" not in internal.NODENAME:
             print("Error: benchcab is currently implemented only on Gadi")
             sys.exit(1)
@@ -102,21 +94,40 @@ def _validate_environment(self, project: str, modules: list):
                 )
                 sys.exit(1)
 
-    def _initialise_tasks(self) -> list[Task]:
+    @functools.cache
+    def _get_config(self, config_path) -> dict:
+        return read_config(config_path)
+
+    @functools.cache
+    def _get_repos(self, config: dict) -> list[CableRepository]:
+        return [
+            CableRepository(**repo_config, repo_id=id)
+            for id, repo_config in enumerate(config["realisations"])
+        ]
+
+    def _initialise_tasks(self, config: dict) -> list[Task]:
         """A helper method that initialises and returns the `tasks` attribute."""
+        repos = [
+            CableRepository(**config, repo_id=id)
+            for id, config in enumerate(config["realisations"])
+        ]
         self.tasks = get_fluxsite_tasks(
-            repos=self.repos,
-            science_configurations=self.config.get(
+            repos=repos,
+            science_configurations=config.get(
                 "science_configurations", internal.DEFAULT_SCIENCE_CONFIGURATIONS
             ),
             fluxsite_forcing_file_names=get_met_forcing_file_names(
-                self.config["experiment"]
+                config["experiment"]
             ),
         )
         return self.tasks
 
-    def fluxsite_submit_job(self) -> None:
+    def fluxsite_submit_job(
+        self, config_path: str, verbose: bool, skip: list[str]
+    ) -> None:
         """Submits the PBS job script step in the fluxsite test workflow."""
+        config = self._get_config(config_path)
+        self._validate_environment(project=config["project"], modules=config["modules"])
         if self.benchcab_exe_path is None:
             msg = "Path to benchcab executable is undefined."
             raise RuntimeError(msg)
@@ -128,21 +139,21 @@ def fluxsite_submit_job(self) -> None:
         )
         with job_script_path.open("w", encoding="utf-8") as file:
             contents = render_job_script(
-                project=self.config["project"],
-                config_path=self.args.config,
-                modules=self.config["modules"],
-                verbose=self.args.verbose,
-                skip_bitwise_cmp="fluxsite-bitwise-cmp" in self.args.skip,
+                project=config["project"],
+                config_path=config_path,
+                modules=config["modules"],
+                verbose=verbose,
+                skip_bitwise_cmp="fluxsite-bitwise-cmp" in skip,
                 benchcab_path=str(self.benchcab_exe_path),
-                pbs_config=self.config.get("fluxsite", {}).get("pbs"),
+                pbs_config=config.get("fluxsite", {}).get("pbs"),
             )
             file.write(contents)
 
         try:
             proc = self.subprocess_handler.run_cmd(
                 f"qsub {job_script_path}",
                 capture_output=True,
-                verbose=self.args.verbose,
+                verbose=verbose,
             )
         except CalledProcessError as exc:
             print("Error when submitting job to NCI queue")
@@ -159,22 +170,25 @@ def fluxsite_submit_job(self) -> None:
             f"{internal.FLUXSITE_DIRS['OUTPUT']}/<task_name>_out.nc"
         )
 
-    def checkout(self):
+    def checkout(self, config_path: str, verbose: bool):
         """Endpoint for `benchcab checkout`."""
+        config = self._get_config(config_path)
+        self._validate_environment(project=config["project"], modules=config["modules"])
+
         mkdir(internal.SRC_DIR, exist_ok=True, verbose=True)
 
         print("Checking out repositories...")
         rev_number_log = ""
-        for repo in self.repos:
-            repo.checkout(verbose=self.args.verbose)
+        for repo in self._get_repos(config):
+            repo.checkout(verbose=verbose)
             rev_number_log += (
                 f"{repo.name} last changed revision: "
                 f"{repo.svn_info_show_item('last-changed-revision')}\n"
             )
 
         # TODO(Sean) we should archive revision numbers for CABLE-AUX
         cable_aux_repo = CableRepository(path=internal.CABLE_AUX_RELATIVE_SVN_PATH)
-        cable_aux_repo.checkout(verbose=self.args.verbose)
+        cable_aux_repo.checkout(verbose=verbose)
 
         rev_number_log_path = self.root_dir / next_path(
             self.root_dir, "rev_number-*.log"
@@ -187,142 +201,108 @@ def checkout(self):
 
         print("")
 
-    def build(self):
+    def build(self, config_path: str, verbose: bool):
         """Endpoint for `benchcab build`."""
-        for repo in self.repos:
+        config = self._get_config(config_path)
+        self._validate_environment(project=config["project"], modules=config["modules"])
+
+        for repo in self._get_repos():
             if repo.build_script:
                 print(
                     "Compiling CABLE using custom build script for "
                     f"realisation {repo.name}..."
                 )
-                repo.custom_build(
-                    modules=self.config["modules"], verbose=self.args.verbose
-                )
+                repo.custom_build(modules=config["modules"], verbose=verbose)
             else:
                 build_mode = "with MPI" if internal.MPI else "serially"
                 print(f"Compiling CABLE {build_mode} for realisation {repo.name}...")
-                repo.pre_build(verbose=self.args.verbose)
-                repo.run_build(
-                    modules=self.config["modules"], verbose=self.args.verbose
-                )
-                repo.post_build(verbose=self.args.verbose)
+                repo.pre_build(verbose=verbose)
+                repo.run_build(modules=config["modules"], verbose=verbose)
+                repo.post_build(verbose=verbose)
             print(f"Successfully compiled CABLE for realisation {repo.name}")
         print("")
 
-    def fluxsite_setup_work_directory(self):
+    def fluxsite_setup_work_directory(self, config_path: str, verbose: bool):
         """Endpoint for `benchcab fluxsite-setup-work-dir`."""
-        tasks = self.tasks if self.tasks else self._initialise_tasks()
+        config = self._get_config(config_path)
+        self._validate_environment(project=config["project"], modules=config["modules"])
+
+        tasks = self.tasks if self.tasks else self._initialise_tasks(config)
         print("Setting up run directory tree for fluxsite tests...")
-        setup_fluxsite_directory_tree(verbose=self.args.verbose)
+        setup_fluxsite_directory_tree(verbose=verbose)
         print("Setting up tasks...")
         for task in tasks:
-            task.setup_task(verbose=self.args.verbose)
+            task.setup_task(verbose=verbose)
         print("Successfully setup fluxsite tasks")
         print("")
 
-    def fluxsite_run_tasks(self):
+    def fluxsite_run_tasks(self, config_path: str, verbose: bool):
         """Endpoint for `benchcab fluxsite-run-tasks`."""
-        tasks = self.tasks if self.tasks else self._initialise_tasks()
+        config = self._get_config(config_path)
+        self._validate_environment(project=config["project"], modules=config["modules"])
+
+        tasks = self.tasks if self.tasks else self._initialise_tasks(config)
         print("Running fluxsite tasks...")
         try:
-            multiprocess = self.config["fluxsite"]["multiprocess"]
+            multiprocess = config["fluxsite"]["multiprocess"]
         except KeyError:
             multiprocess = internal.FLUXSITE_DEFAULT_MULTIPROCESS
         if multiprocess:
-            ncpus = self.config.get("pbs", {}).get(
+            ncpus = config.get("pbs", {}).get(
                 "ncpus", internal.FLUXSITE_DEFAULT_PBS["ncpus"]
             )
-            run_tasks_in_parallel(tasks, n_processes=ncpus, verbose=self.args.verbose)
+            run_tasks_in_parallel(tasks, n_processes=ncpus, verbose=verbose)
         else:
-            run_tasks(tasks, verbose=self.args.verbose)
+            run_tasks(tasks, verbose=verbose)
         print("Successfully ran fluxsite tasks")
         print("")
 
-    def fluxsite_bitwise_cmp(self):
+    def fluxsite_bitwise_cmp(self, config_path: str, verbose: bool):
         """Endpoint for `benchcab fluxsite-bitwise-cmp`."""
+        config = self._get_config(config_path)
+        self._validate_environment(project=config["project"], modules=config["modules"])
+
         if not self.modules_handler.module_is_loaded("nccmp/1.8.5.0"):
             self.modules_handler.module_load(
                 "nccmp/1.8.5.0"
             )  # use `nccmp -df` for bitwise comparisons
 
-        tasks = self.tasks if self.tasks else self._initialise_tasks()
+        tasks = self.tasks if self.tasks else self._initialise_tasks(config)
         comparisons = get_fluxsite_comparisons(tasks)
 
         print("Running comparison tasks...")
         try:
-            multiprocess = self.config["fluxsite"]["multiprocess"]
+            multiprocess = config["fluxsite"]["multiprocess"]
         except KeyError:
             multiprocess = internal.FLUXSITE_DEFAULT_MULTIPROCESS
         if multiprocess:
             try:
-                ncpus = self.config["fluxsite"]["pbs"]["ncpus"]
+                ncpus = config["fluxsite"]["pbs"]["ncpus"]
             except KeyError:
                 ncpus = internal.FLUXSITE_DEFAULT_PBS["ncpus"]
-            run_comparisons_in_parallel(
-                comparisons, n_processes=ncpus, verbose=self.args.verbose
-            )
+            run_comparisons_in_parallel(comparisons, n_processes=ncpus, verbose=verbose)
         else:
-            run_comparisons(comparisons, verbose=self.args.verbose)
+            run_comparisons(comparisons, verbose=verbose)
         print("Successfully ran comparison tasks")
 
-    def fluxsite(self):
+    def fluxsite(
+        self, config_path: str, no_submit: bool, verbose: bool, skip: list[str]
+    ):
         """Endpoint for `benchcab fluxsite`."""
-        self.checkout()
-        self.build()
-        self.fluxsite_setup_work_directory()
-        if self.args.no_submit:
-            self.fluxsite_run_tasks()
-            if "fluxsite-bitwise-cmp" not in self.args.skip:
-                self.fluxsite_bitwise_cmp()
+        self.checkout(config_path, verbose)
+        self.build(config_path, verbose)
+        self.fluxsite_setup_work_directory(config_path, verbose)
+        if no_submit:
+            self.fluxsite_run_tasks(config_path, verbose)
+            if "fluxsite-bitwise-cmp" not in skip:
+                self.fluxsite_bitwise_cmp(config_path, verbose)
         else:
-            self.fluxsite_submit_job()
+            self.fluxsite_submit_job(config_path, verbose, skip)
 
-    def spatial(self):
+    def spatial(self, config_path: str, verbose: bool):
         """Endpoint for `benchcab spatial`."""
 
-    def run(self):
+    def run(self, config_path: str, no_submit: bool, verbose: bool, skip: list[str]):
         """Endpoint for `benchcab run`."""
-        self.fluxsite()
-        self.spatial()
-
-    def main(self):
-        """Main function for `benchcab`."""
-        if self.args.subcommand == "run":
-            self.run()
-
-        if self.args.subcommand == "checkout":
-            self.checkout()
-
-        if self.args.subcommand == "build":
-            self.build()
-
-        if self.args.subcommand == "fluxsite":
-            self.fluxsite()
-
-        if self.args.subcommand == "fluxsite-setup-work-dir":
-            self.fluxsite_setup_work_directory()
-
-        if self.args.subcommand == "fluxsite-submit-job":
-            self.fluxsite_submit_job()
-
-        if self.args.subcommand == "fluxsite-run-tasks":
-            self.fluxsite_run_tasks()
-
-        if self.args.subcommand == "fluxsite-bitwise-cmp":
-            self.fluxsite_bitwise_cmp()
-
-        if self.args.subcommand == "spatial":
-            self.spatial()
-
-
-def main():
-    """Main program entry point for `benchcab`.
-
-    This is required for setup.py entry_points
-    """
-    app = Benchcab(argv=sys.argv, benchcab_exe_path=shutil.which(sys.argv[0]))
-    app.main()
-
-
-if __name__ == "__main__":
-    main()
+        self.fluxsite(config_path, no_submit, verbose, skip)
+        self.spatial(config_path, verbose)