Use PrecompileTools for artifact resolution

.gitignore

@@ -13,3 +13,6 @@ benchmark/tune.json
 # Pkg
 deps/build.log
 /Manifest.toml
+
+# VSCode settings
+.vscode/settings.json

Project.toml

@@ -9,6 +9,7 @@ Dates = "ade2ca70-3891-5945-98fb-dc099432e06a"
 Downloads = "f43a241f-c20a-4ad4-852c-f6b1247861c6"
 InlineStrings = "842dd82b-1e85-43dc-bf29-5d0ee9dffc48"
 Mocking = "78c3b35d-d492-501b-9361-3d52fe80e533"
+PrecompileTools = "aea7be01-6a6a-4083-8856-8a6e6704d82a"
 Printf = "de0858da-6303-5e67-8744-51eddeeeb8d7"
 RecipesBase = "3cdcf5f2-1ef4-517c-9805-6587b60abb01"
 Scratch = "6c6a2e73-6563-6170-7368-637461726353"
@@ -23,6 +24,7 @@ Dates = "1"
 Downloads = "1"
 InlineStrings = "1"
 Mocking = "0.7, 0.8"
+PrecompileTools = "1"
 Printf = "1"
 RecipesBase = "0.7, 0.8, 1"
 Scratch = "1.1.1"

src/TimeZones.jl

@@ -2,6 +2,7 @@ module TimeZones
 
 using Artifacts: Artifacts
 using Dates
+using PrecompileTools: @compile_workload, @setup_workload
 using Printf
 using Scratch: @get_scratch!
 using Unicode
@@ -40,20 +41,22 @@ const _COMPILED_DIR = Ref{String}()
 # abstract type UTC <: TimeZone end  # Already defined in the Dates stdlib
 abstract type Local <: TimeZone end
 
+# Resolve the TZJData artifact directory using direct function calls that the
+# juliac trimmer can trace. We intentionally avoid TZJData.artifact_dir() which
+# uses the @artifact_str macro — that macro expands to Base.invokelatest(...),
+# an opaque dynamic dispatch barrier the trimmer cannot follow through, causing
+# the callee to be removed from trimmed binaries.
+function _resolve_tzjdata_dir()
+    pkg = Base.identify_package(TZJData, "TZJData")
+    pkg_dir = dirname(dirname(Base.locate_package(pkg)))
+    artifact_dict = Artifacts.parse_toml(joinpath(pkg_dir, "Artifacts.toml"))
+    hash = Base.SHA1(artifact_dict["tzjdata"]["git-tree-sha1"])
+    return Artifacts.artifact_path(hash)
+end
+
 function __init__()
     # Set at runtime to ensure relocatability
-    _COMPILED_DIR[] = @static if isdefined(TZJData, :artifact_dir)
-        TZJData.artifact_dir()
-    else
-        # Backwards compatibility for TZJData versions below v1.3.1. The portion of the
-        # code which determines the `pkg_dir` could be replaced by `pkgdir(TZJData)` however
-        # the `pkgdir` function doesn't work well with relocated system images.
-        pkg = Base.identify_package(TZJData, "TZJData")
-        pkg_dir = dirname(dirname(Base.locate_package(pkg)))
-        artifact_dict = Artifacts.parse_toml(joinpath(pkg_dir, "Artifacts.toml"))
-        hash = Base.SHA1(artifact_dict["tzjdata"]["git-tree-sha1"])
-        Artifacts.artifact_path(hash)
-    end
+    _COMPILED_DIR[] = _resolve_tzjdata_dir()
 
     # Dates extension needs to happen everytime the module is loaded (issue #24)
     init_dates_extension()
@@ -97,4 +100,31 @@ if !isdefined(Base, :get_extension)
     include("../ext/TimeZonesRecipesBaseExt.jl")
 end
 
+# Ensure methods used in __init__ are preserved by juliac --trim (requires Julia >= 1.12).
+# The trimmer only keeps methods reachable from @ccallable entry points and precompiled
+# methods. This workload exercises the __init__ code paths so the trimmer retains them.
+# On Julia < 1.9, @compile_workload still executes the code but doesn't cache native code
+@setup_workload begin
+    @compile_workload begin
+        # Preserve artifact resolution methods needed by __init__.
+        _resolve_tzjdata_dir()
+
+        @static if VERSION >= v"1.9"
+            # Also sets _COMPILED_DIR so the TimeZone("UTC") call below can load tzdata.
+            _COMPILED_DIR[] = _resolve_tzjdata_dir()
+
+            # Exercise core timezone functionality so timezone loading methods
+            # are also preserved.
+            TimeZone("UTC")
+
+            # Reset the cache so it doesn't persist into the loaded module with
+            # stale data from the precompilation environment. Without this, the
+            # cache's `initialized` flag stays true and `_build()` is never called
+            # at runtime — breaking `JULIA_TZ_VERSION` overrides and any scenario
+            # where the compiled tzdata differs from what was available here.
+            copy!(_TZ_CACHE, TimeZoneCache())
+        end
+    end
+end
+
 end # module