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jimmyfrasche opened this issue Jan 28, 2018 · 6 comments
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go/build: erroneous contents for Doc field in *Package for image package #23594

jimmyfrasche opened this issue Jan 28, 2018 · 6 comments
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FrozenDueToAge NeedsFix The path to resolution is known, but the work has not been done.
Milestone
Go1.11

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@jimmyfrasche
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go list -f '{{.Doc}}' image

and

go1.10rc1 list -f '{{.Doc}}' image

and

package main

import (
	"fmt"
	"go/build"
	"log"
)

func main() {
	pkg, err := build.Import("image", "", 0)
	if err != nil {
		log.Fatal(err)
	}
	fmt.Println(pkg.Doc)
}

all print

This example demonstrates decoding a JPEG image and examining its pixels.

rather than

Package image implements a basic 2-D image library.

which is the correct package synopsis.

The erroneous synopsis comes from the package documentation of the image_test package which provides the package-level Example.

It's possible that other packages are effected but this is the only one I found.

From a cursory look at *go/build.Context.Import it appears that this is caused by the loop grabbing the first synopsis found in any file (lines 816-818 below) when it seems as if it should ignore test and xtest files using the variables isTest and isXTest

go/src/go/build/build.go

Lines 798 to 818 in 00587e8

isTest := strings.HasSuffix(name, "_test.go")
isXTest := false
if isTest && strings.HasSuffix(pkg, "_test") {
isXTest = true
pkg = pkg[:len(pkg)-len("_test")]
}
if p.Name == "" {
p.Name = pkg
firstFile = name
} else if pkg != p.Name {
badFile(&MultiplePackageError{
Dir: p.Dir,
Packages: []string{p.Name, pkg},
Files: []string{firstFile, name},
})
p.InvalidGoFiles = append(p.InvalidGoFiles, name)
}
if pf.Doc != nil && p.Doc == "" {
p.Doc = doc.Synopsis(pf.Doc.Text())
}

System details

go version go1.9.3 linux/amd64
GOARCH="amd64"
GOBIN="/home/jimmy/bin"
GOEXE=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOOS="linux"
GOPATH="/home/jimmy/code/go"
GORACE=""
GOROOT="/home/jimmy/ext/go"
GOTOOLDIR="/home/jimmy/ext/go/pkg/tool/linux_amd64"
GCCGO="gccgo"
CC="gcc"
GOGCCFLAGS="-fPIC -m64 -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build433721585=/tmp/go-build -gno-record-gcc-switches"
CXX="g++"
CGO_ENABLED="1"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOROOT/bin/go version: go version go1.9.3 linux/amd64
GOROOT/bin/go tool compile -V: compile version go1.9.3
uname -sr: Linux 4.13.0-1-amd64
Distributor ID:	Debian
Description:	Debian GNU/Linux testing (buster)
Release:	testing
Codename:	buster
/lib/x86_64-linux-gnu/libc.so.6: GNU C Library (Debian GLIBC 2.26-4) stable release version 2.26, by Roland McGrath et al.
gdb --version: GNU gdb (Debian 7.12-6+b1) 7.12.0.20161007-git
@jimmyfrasche
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I would have put the bit of code on the playground but using go/build doesn't work there. Is that another bug or just a limitation of the playground?

@ianlancetaylor ianlancetaylor added the NeedsFix The path to resolution is known, but the work has not been done. label Jan 29, 2018
@ianlancetaylor ianlancetaylor added this to the Go1.11 milestone Jan 29, 2018
@josharian
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Nice find.

I would have put the bit of code on the playground but using go/build doesn't work there. Is that another bug or just a limitation of the playground?

Depends on how you view it. The playground's filesystem is fake -- see "Faking the file system" in https://blog.golang.org/playground. It can be prepopulated, so we could prepopulate it with the standard library. But I don't really think that'd be worth the effort.

FWIW, I actually prefer pasted code to playground links, at least for small bits of code. Making skimming issues easier, particularly on my phone.

@jimmyfrasche
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@josharian fair enough, filed #23603 nonetheless, since it would be useful albeit niche.

(anchored link to section Faking the file system)

@mvdan
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mvdan commented Feb 19, 2018

@jimmyfrasche it seems like you described a patch above - why not send it as a CL?

@gopherbot
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Change https://golang.org/cl/96976 mentions this issue: go/build: correct value of .Doc field

@jimmyfrasche
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@mvdan a fatal combination of laziness and forgetfulness—thanks for the reminder!

In testing I found this issue also affected the flag and container/heap packages.

@jimmyfrasche jimmyfrasche mentioned this issue Mar 11, 2018
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FrozenDueToAge NeedsFix The path to resolution is known, but the work has not been done.
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@josharian @jimmyfrasche @ianlancetaylor @mvdan @gopherbot