Add test for dependencies

Adding new dependencies to a Julia project has downsides. First, every
dependency increases the precompilation and import time of a package. For
complex packages, such as CUDA, this translates in several minutes of
precompilation time that every single user of ClimaAtmos (including our CI
runners) always pays. Second, dependencies can increase the cost of maintaining
ClimaAtmos and the surface area of things that can go wrong (a buggy update in a
dependency can break ClimaAtmos). Third, dependencies increase the complexity of
the project's environment, potentially causing compatibility issues and
restricting the versions we can use.

This new test follows the spirit of the regression tests and tries to capture
the cost of adding a new dependency by having developers explicitly come here
and

test/dependencies.jl

@@ -0,0 +1,87 @@
+import Pkg
+import Test
+
+# Adding new dependencies to a Julia project has downsides. First, every
+# dependency increases the precompilation and import time of a package. For
+# complex packages, such as CUDA, this translates in several minutes of
+# precompilation time that every single user of ClimaAtmos (including our CI
+# runners) always pays. Second, dependencies can increase the cost of
+# maintaining ClimaAtmos and the surface area of things that can go wrong (a
+# buggy update in a dependency can break ClimaAtmos). Third, dependencies
+# increase the complexity of the project's environment, potentially causing
+# compatibility issues and restricting the versions we can use.
+
+# This test follows the spirit of the regression tests and tries to capture the
+# cost of adding a new dependency by having developers explicitly come here and
+# declare their intents.
+#
+# DO NOT ADD new dependencies if:
+
+# - the feature you need can be easily implemented (e.g., do you need the might
+#   of Distributions.jl to compute a guassian function?)
+# - your dependency is heavy/has lots of dependencies (e.g., DataFrames, CUDA).
+#   Instead, ask around, someone will help you accomplish what you need
+# - your dependency implements code that logically should be implemented elsewhere
+#   (e.g., if your importing CUDA, maybe we should extend ClimaComms instead).
+#   Instead, ask around, someone will help you accomplish what you need
+
+atmos_uuid = Pkg.project().dependencies["ClimaAtmos"]
+direct_dependencies =
+    keys(Pkg.dependencies(identity, atmos_uuid).dependencies) |> Set
+
+known_dependencies = Set([
+    # Adapt is used to generate the spline for Earth topography
+    "Adapt",
+    # ArgParse is used to read --config_file and --job_id from command line
+    "ArgParse",
+    # ArtifactWrappers is used to topography and gravity wave NetCDF data
+    "ArtifactWrappers",
+    "Artifacts",
+    "AtmosphericProfilesLibrary",
+    "ClimaComms",
+    "ClimaCore",
+    "ClimaDiagnostics",
+    "ClimaParams",
+    "ClimaTimeSteppers",
+    "ClimaUtilities",
+    "CloudMicrophysics",
+    "Dates",
+    "DiffEqBase",
+    "FastGaussQuadrature",
+    "Insolation",
+    "Interpolations",
+    "LazyArtifacts",
+    "LinearAlgebra",
+    "Logging",
+    # NCDatasets is used to read Earth topography, GCM driven initial conditions, orographic gravity wave data
+    "NCDatasets",
+    "NVTX",
+    # Pkg is used to download the RRTMGP artifact
+    "Pkg",
+    "RRTMGP",
+    "SciMLBase",
+    "StaticArrays",
+    # Statistics is used to call 'mean' on ClimaCore Fields
+    "Statistics",
+    "SurfaceFluxes",
+    "Thermodynamics",
+    "YAML",
+])
+
+diff = setdiff(direct_dependencies, known_dependencies)
+
+if !isempty(diff)
+    println("Detected new dependencies: $diff")
+    println("Please, double check if you really need the new dependencies")
+    println(
+        "If you do, edit the dependencies.jl file adding a note about where the packages are used",
+    )
+end
+
+otherdiff = setdiff(known_dependencies, direct_dependencies)
+if !isempty(otherdiff)
+    println("Detected stale dependencies: $otherdiff")
+    println("Please, edit the dependencies.jl file")
+end
+
+Test.@test direct_dependencies == known_dependencies

test/runtests.jl

@@ -9,6 +9,7 @@ using Test
 
 #! format: off
 @safetestset "Aqua" begin @time include("aqua.jl") end
+@safetestset "Dependencies" begin @time include("dependencies.jl") end
 @safetestset "Callbacks" begin @time include("callbacks.jl") end
 @safetestset "Utilities" begin @time include("utilities.jl") end
 @safetestset "Parameter tests" begin @time include("parameters/parameter_tests.jl") end