time: misleading "zoneinfo.zip: no such file or directory" error when trying to load non-existent timezone

[Dieterbe]

Please answer these questions before submitting your issue. Thanks!

What version of Go are you using (go version)?

go version devel +be855e3f28 Mon Jun 19 23:26:32 2017 +0000 linux/amd64

What operating system and processor architecture are you using (go env)?

GOARCH="amd64"
GOBIN=""
GOEXE=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOOS="linux"
GOPATH="/home/dieter/go"
GORACE=""
GOROOT="/home/dieter/code/go"
GOTOOLDIR="/home/dieter/code/go/pkg/tool/linux_amd64"
GCCGO="gccgo"
CC="gcc"
GOGCCFLAGS="-fPIC -m64 -fmessage-length=0 -fdebug-prefix-map=/tmp/dieter/go-build409613068=/tmp/go-build -gno-record-gcc-switches"
CXX="g++"
CGO_ENABLED="0"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"

What did you do?

> cat main.go
package main

import (
	"fmt"
	"time"
)

func main() {
	tz, err := time.LoadLocation("America/New_York")
	fmt.Printf("New_York %q %q\n", tz, err)
	tz, err = time.LoadLocation("America/New_Yaark")
	fmt.Printf("New_Yaark %q %q\n", tz, err)
}
> cat Dockerfile
FROM alpine
RUN apk add -U tzdata
COPY main /usr/bin/
ENTRYPOINT ["/usr/bin/main"]

go build -o main
docker build .
docker run ea1f31431e4d

What did you expect to see?

New_York "America/New_York" %!q(<nil>)
New_Yaark "UTC" "can't find timezone America/New_Yaark or something"

What did you see instead?

New_York "America/New_York" %!q(<nil>)
New_Yaark "UTC" "open /home/dieter/code/go/lib/time/zoneinfo.zip: no such file or directory"

note that when I run it on my host which does have a zoneinfo.zip I get:

go run main.go
New_York "America/New_York" %!q(<nil>)
New_Yaark "UTC" "cannot find America/New_Yaark in zip file /home/dieter/code/go/lib/time/zoneinfo.zip"

[bradfitz]

Not a regression from Go 1.8 (or any other prior release), so targeting Go 1.10 for consideration.

I don't think it's a good idea to get rid of the part of the error message that says where it was looking to find the answer (which zip file path). You want it to say both things? Failed to find New_Yaark and also the zip file path?

[Dieterbe]

i'm not sure TBH. to be clear, is it perfectly normal to have situations where only a few timezones are installed, and where it can only know for sure that a tz doesn't exist if it can check against a zoneinfo.zip file?

[ALTree]

@Dieterbe the alternative would be to embed the whole IANA Time Zone database in the binary(?)

I agree we could try to print a better error, though (even if the current one is technically correct).

[bradfitz]

@ALTree, some discussion of that is in #20629 (comment).

[Dieterbe]

can somebody answer:

to be clear, is it perfectly normal to have situations where only a few timezones are installed, and where it can only know for sure that a tz doesn't exist if it can check against a zoneinfo.zip file?

(i hope that question did not come across snarky or sarcastic. I just need clarity on that before I can think of suggestions for improvement)

[bradfitz]

@Dieterbe, oh, I see what you're suggesting now. That if, say, /usr/share/zoneinfo exists on disk and is not empty, that it's the only source of truth and that the zip file shouldn't be used as a backup (and thus the error message of its non-existence would never occur).

That's a possibility. I don't believe the intent of the current code is to blend two sources of information (zoneinfo dir and zip), but just to try the zip if the file on disk doesn't exist. IIRC, currently the code just tries to open a single file under /usr/share/zoneinfo and doesn't try to determine whether sibling files exist.