Copy preferences into the test environment

[davidanthoff]

Finishes the work started in #97 (whose commit is cherry-picked here, so @NHDaly keeps authorship of it) and closes #59.

Pkg.test copies the merged preferences into the sandbox it builds; TestEnv did not, so packages whose tests are configured through Preferences.jl pass under ]test but not under TestEnv.activate(). This ports Pkg's logic across.

What changed on top of #97

• Extended to every version directory that can support it. Support Preferences in TestEnv: Copy the preferences into the TestEnv. #97 patched src/julia-1.9 only, which covers Julia 1.9–1.10. The lookup now lives in common.jl as sandbox_preferences and is applied in julia-1.8, julia-1.9, julia-1.11, julia-1.12 and julia-1.13.
• The do-block form is fixed too. TestEnv.activate(f, pkg) delegates to Pkg.Operations.sandbox, which has taken a preferences= keyword since Julia 1.8 but was never passed one — so that form dropped preferences even with the set form fixed.
• Empty-preferences guard. Base.get_preferences() returns an empty Dict, not nothing, so the !== nothing check always fired and always wrote an empty preferences file. It now guards on !isempty.
• Dropped the source_path local that shadowed Pkg.Operations.source_path, qualified copy!(Base.LOAD_PATH, ...) in the restore path, and answered the # TODO: should we separately import TOML? in a comment — no, TestEnv supports Julia 1.0, which predates the TOML stdlib, so Pkg.TOML it is.

Why not Julia 1.7 and earlier

Base.get_preferences only grew its no-argument, whole-set form in Julia 1.8; before that it (and collect_preferences) is scoped to a single package UUID, so there is no way to collect the full merged set to copy across without reimplementing Base's merge. Pkg.Operations.sandbox likewise only gained its preferences= keyword in 1.8. Older versions keep today's behaviour, and the README now says so.

Tests

Three offline fixture packages under test/preferences/ — no registry dependencies, so they instantiate without network:

• PrefsTopLevel — preferences at the package root, no test/Project.toml
• PrefsTestDir — a test/ environment whose preferences shadow the package root's, with one key only set at the root to check the merge order
• PrefsNone — no preferences at all, to cover the isempty guard

Both activate forms are covered. Verified that all of these fail on main and pass here.

Drive-by fix

test/activate_set.jl's precompile testset guarded its finally with isdefined(@__MODULE__, :orig_load_path) — those are locals inside the testset, not module globals, so the guard was never true and LOAD_PATH/DEPOT_PATH leaked into every later testset. Restoring them unconditionally is needed for the new tests to mean anything.

Verification

Full suite run locally against Julia 1.6.7, 1.8.5, 1.9.4, 1.11.9, 1.12.7 and 1.13.0-rc3 — all pass.

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 83.36%. Comparing base (1766d3f) to head (5386d88).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #121      +/-   ##
==========================================
+ Coverage   81.69%   83.36%   +1.67%     
==========================================
  Files          34       34              
  Lines         945     1040      +95     
==========================================
+ Hits          772      867      +95     
  Misses        173      173              

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