Added tests for load_overrides() in Artifacts.jl (JuliaLang#51833)

Fixes JuliaLang#48551
Continued from JuliaLang#51815
The `load_overrides()` method in `Artifacts.jl` has a large untested
branch. This PR increases the test coverage for this method.


![image](https://github.com/JuliaLang/julia/assets/141328479/a9744e25-e79f-4664-8522-320dd29c4c50)

https://app.codecov.io/gh/JuliaLang/julia/blob/master/stdlib%2FArtifacts%2Fsrc%2FArtifacts.jl#L121

stdlib/Artifacts/test/runtests.jl

@@ -2,12 +2,91 @@
 import Base: SHA1
 
 using Artifacts, Test, Base.BinaryPlatforms
-using Artifacts: with_artifacts_directory, pack_platform!, unpack_platform
+using Artifacts: with_artifacts_directory, pack_platform!, unpack_platform, load_overrides
+using TOML
 
 # prepare for the package tests by ensuring the required artifacts are downloaded now
 artifacts_dir = mktempdir()
 run(addenv(`$(Base.julia_cmd()) --color=no $(joinpath(@__DIR__, "refresh_artifacts.jl")) $(artifacts_dir)`, "TERM"=>"dumb"))
 
+@testset "Load Overrides" begin
+ """
+ create_test_overrides_toml(temp_dir::String)
+
+ Create "Overrides.toml" in the given `temp_dir`.
+ """
+ function create_test_overrides_toml(temp_dir::String)
+ # Define the overrides
+ overrides = Dict(
+ "78f35e74ff113f02274ce60dab6e92b4546ef806" => "/path/to/replacement",
+ "c76f8cda85f83a06d17de6c57aabf9e294eb2537" => "fb886e813a4aed4147d5979fcdf27457d20aa35d",
+ "d57dbccd-ca19-4d82-b9b8-9d660942965b" => Dict(
+ "c_simple" => "/path/to/c_simple_dir",
+ "libfoo" => "fb886e813a4aed4147d5979fcdf27457d20aa35d"
+ )
+ )
+
+ # Get the artifacts directory
+ artifacts_dir = joinpath(temp_dir, "artifacts")
+
+ # Ensure the artifacts directory exists
+ isdir(artifacts_dir) || mkdir(artifacts_dir)
+
+ # Get the path to the Overrides.toml file
+ overrides_path = joinpath(artifacts_dir, "Overrides.toml")
+
+ # Create the Overrides.toml file
+ open(overrides_path, "w") do io
+ TOML.print(io, overrides)
+ end
+ end
+
+ # Specify the expected test result when depot path does not exist or no overriding happened
+ empty_output = Dict{Symbol, Any}(
+ :UUID => Dict{Base.UUID, Dict{String, Union{SHA1, String}}}(),
+ :hash => Dict{SHA1, Union{SHA1, String}}()
+ )
+
+ # Specify the expected test result when overriding happened
+ expected_output = Dict{Symbol, Any}(
+ :UUID => Dict{Base.UUID, Dict{String, Union{SHA1, String}}}(Base.UUID("d57dbccd-ca19-4d82-b9b8-9d660942965b") => Dict("c_simple" => "/path/to/c_simple_dir", "libfoo" => SHA1("fb886e813a4aed4147d5979fcdf27457d20aa35d"))),
+ :hash => Dict{SHA1, Union{SHA1, String}}(SHA1("78f35e74ff113f02274ce60dab6e92b4546ef806") => "/path/to/replacement", SHA1("c76f8cda85f83a06d17de6c57aabf9e294eb2537") => SHA1("fb886e813a4aed4147d5979fcdf27457d20aa35d"))
+ )
+
+ # Test `load_overrides()` works with *no* "Overrides.toml" file
+ @test load_overrides() == empty_output
+
+ # Create a temporary directory
+ mktempdir() do temp_dir
+ # Back up the old `DEPOT_PATH``
+ old_depot_path = copy(Base.DEPOT_PATH)
+
+ # Set `DEPOT_PATH` to that directory
+ empty!(Base.DEPOT_PATH)
+ push!(Base.DEPOT_PATH, temp_dir)
+
+ try
+ # Create "Overrides.toml" for the test
+ create_test_overrides_toml(temp_dir)
+
+ # Test `load_overrides()` works *with* "Overrides.toml" file but non-nothing ARTIFACT_OVERRIDES[]
+ @test load_overrides() == empty_output
+
+ # Test `load_overrides()` works *with* "Overrides.toml" file with force parameter, which overrides even when `ARTIFACT_OVERRIDES[] !== nothing``
+ @test load_overrides(force=true) == expected_output
+ finally # Make sure `DEPOT_PATH` will be restored to the status quo in the event of a bug
+ # Restore the old `DEPOT_PATH` to avoid messing with any other code
+ empty!(Base.DEPOT_PATH)
+ append!(Base.DEPOT_PATH, old_depot_path)
+ end
+ end
+ # Temporary directory and test "Overrides.toml" file will be automatically deleted when out of scope
+ # This means after this block, the system *should* behave like this test never happened.
+
+ # Test the "Overrides.toml" file is cleared back to the status quo
+ @test load_overrides(force=true) == empty_output
+end
+
 @testset "Artifact Paths" begin
  mktempdir() do tempdir
  with_artifacts_directory(tempdir) do