fix: fall back to UTC if localzone() fails (#7)

* fix: fall back to UTC if localzone fails

* move _localtz into a separate function

* add changelog, set version to 0.1.2

* fix doctest env

CHANGELOG.md

@@ -2,7 +2,13 @@
 
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/), and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
-## Unreleased
+## Version v0.1.2 - 2023-06-26
+
+### Fixed
+
+* If TimeZones.jl fails to determine the system's timezone, JuliaHub.jl now gracefully falls back to UTC to represent dates and times. (#7)
+
+## Version v0.1.1 - 2023-06-24
 
 ### Added
 

Project.toml

@@ -1,7 +1,7 @@
 name = "JuliaHub"
 uuid = "bc7fa6ce-b75e-4d60-89ad-56c957190b6e"
 authors = ["JuliaHub Inc."]
-version = "0.1.1"
+version = "0.1.2"
 
 [deps]
 Base64 = "2a0f44e3-6c83-55bd-87e4-b1978d98bd5f"

docs/make.jl

@@ -1,9 +1,11 @@
 using JuliaHub
 using Documenter, DocumenterMermaid
+import TimeZones
 
 # Timestamp printing is dependent on the timezone, so we force a specific (non-UTC)
 # timezone to make sure that the doctests don't fail because of timezone differences.
 ENV["TZ"] = "America/New_York"
+JuliaHub._LOCAL_TZ[] = TimeZones.localzone()
 
 DocMeta.setdocmeta!(
     JuliaHub, :DocTestSetup,

src/JuliaHub.jl

@@ -13,6 +13,8 @@ import TOML
 import URIs
 import UUIDs
 
+const _LOCAL_TZ = Ref{Dates.TimeZone}()
+
 include("utils.jl")
 include("authentication.jl")
 include("restapi.jl")
@@ -28,4 +30,11 @@ include("jobs/logging.jl")
 include("jobs/logging-kafka.jl")
 include("jobs/logging-legacy.jl")
 
+function __init__()
+    # We'll only attempt to determine the local timezone once, when the package loads,
+    # and store the result in a global. This way all timestamps will have consistent timezones
+    # even if something in the environment changes.
+    _LOCAL_TZ[] = _localtz()
+end
+
 end

src/utils.jl

@@ -350,7 +350,7 @@ end
 _utc2localtz(timestamp::Number) = _utc2localtz(Dates.unix2datetime(timestamp))
 function _utc2localtz(datetime_utc::Dates.DateTime)::TimeZones.ZonedDateTime
     datetimez_utc = TimeZones.ZonedDateTime(datetime_utc, TimeZones.tz"UTC")
-    return TimeZones.astimezone(datetimez_utc, TimeZones.localzone())
+    return TimeZones.astimezone(datetimez_utc, _LOCAL_TZ[])
 end
 # Special version of _utc2localtz to handle integer ms timestamp
 function _ms_utc2localtz(timestamp::Integer)::TimeZones.ZonedDateTime
@@ -397,5 +397,17 @@ function _parse_tz(timestamp_str::AbstractString; msg::Union{AbstractString, Not
         end
         throw(JuliaHubError(errmsg))
     end
-    return TimeZones.astimezone(timestamp, TimeZones.localzone())
+    return TimeZones.astimezone(timestamp, _LOCAL_TZ[])
+end
+
+# It's quite easy to make TimeZones.localzone() fail and throw.
+# So this wraps it, and adds a UTC fallback (which seems like the sensible
+# default) in the case where somehow the local timezone is not configured properly.
+function _localtz()
+    try
+        TimeZones.localzone()
+    catch e
+        @debug "Unable to determine local timezone" exception = (e, catch_backtrace())
+        TimeZones.tz"UTC"
+    end
 end

test/utils.jl

@@ -52,25 +52,26 @@ end
 end
 
 @testset "_parse_tz" begin
+    @test isassigned(JuliaHub._LOCAL_TZ)
     let t = JuliaHub._parse_tz("2022-10-12T05:30:31.1+00:00")
         @test t isa TimeZones.ZonedDateTime
-        @test t.timezone == TimeZones.localzone()
+        @test t.timezone == JuliaHub._LOCAL_TZ[]
         @test Dates.millisecond(t) == 100
     end
     let t = JuliaHub._parse_tz("2022-10-12T05:30:31.12+00:00")
         @test t isa TimeZones.ZonedDateTime
-        @test t.timezone == TimeZones.localzone()
+        @test t.timezone == JuliaHub._LOCAL_TZ[]
         @test Dates.millisecond(t) == 120
     end
     let t = JuliaHub._parse_tz("2022-10-12T05:30:31.123+00:00")
         @test t isa TimeZones.ZonedDateTime
-        @test t.timezone == TimeZones.localzone()
+        @test t.timezone == JuliaHub._LOCAL_TZ[]
         @test Dates.millisecond(t) == 123
     end
     @test_throws JuliaHub.JuliaHubError JuliaHub._parse_tz("2022-10-12T05:30:31.+00:00")
     let t = JuliaHub._parse_tz("2022-10-12T05:30:31+00:00")
         @test t isa TimeZones.ZonedDateTime
-        @test t.timezone == TimeZones.localzone()
+        @test t.timezone == JuliaHub._LOCAL_TZ[]
         @test Dates.millisecond(t) == 0
     end
     @test_throws JuliaHub.JuliaHubError JuliaHub._parse_tz("")