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go/build: build.Import finds empty directories as packages #16898

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Warashi opened this issue Aug 27, 2016 · 4 comments
Closed

go/build: build.Import finds empty directories as packages #16898

Warashi opened this issue Aug 27, 2016 · 4 comments
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@Warashi
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Warashi commented Aug 27, 2016

Please answer these questions before submitting your issue. Thanks!

  1. What version of Go are you using (go version)?
go version go1.7 darwin/amd64
  1. What operating system and processor architecture are you using (go env)?
GOARCH="amd64"
GOBIN=""
GOEXE=""
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GOOS="darwin"
GOPATH="/Users/sawada/go"
GORACE=""
GOROOT="/usr/local/Cellar/go/1.7/libexec"
GOTOOLDIR="/usr/local/Cellar/go/1.7/libexec/pkg/tool/darwin_amd64"
CC="clang"
GOGCCFLAGS="-fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/49/rrmkxj1n1db593lnjqln1__h0000gn/T/go-build349947113=/tmp/go-build -gno-record-gcc-switches -fno-common"
CXX="clang++"
CGO_ENABLED="1"
  1. What did you do?
package main

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

func main() {
    gopath := os.Getenv("GOPATH")
    _, err := build.Import("bar", gopath+"/src/foo", build.FindOnly)
    if err != nil {
        fmt.Println(err)
    }
}
$ mkdir -p $GOPATH/src/foo
$ cd $GOPATH/src/foo
$ mkdir -p vendor/bar
$ cat ABOVE_CODE > main.go
$ go run main.go
  1. What did you expect to see?
    nothing
  2. What did you see instead?
cannot find package "bar" in any of:
    /Users/sawada/go/src/foo/vendor/bar (vendor tree)
    /usr/local/Cellar/go/1.7/libexec/src/bar (from $GOROOT)
    /Users/sawada/go/src/bar (from $GOPATH)
@quentinmit
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An empty directory is not a package. Quoth ref/spec: "A package in turn is constructed from one or more source files"

I'm going to close this as WAI. Was there a particular reason you expected it to find the empty bar directory?

@Warashi
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Warashi commented Sep 7, 2016

But when bar directory is in $GOPATH/src, build.Import finds bar and returned err is nil.
So there is difference between $GOPATH/src and vendor.
Isn't this a problem?

@quentinmit
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That does seem odd, I agree. The behavior seems to match the documentation, though. This is also covered in the vendoring spec:

https://docs.google.com/document/d/1Bz5-UB7g2uPBdOx-rw5t9MxJwkfpx90cqG9AFL0JAYo/edit

If there is a source directory d/vendor, then, when compiling a source file within the subtree rooted at d, import "p" is interpreted as import "d/vendor/p" if that path names a directory containing at least one file with a name ending in “.go”.

So if anything, the bug is that build.Import /does/ find the non-vendored directory.

/cc @rsc Is this WAI?

@quentinmit quentinmit reopened this Sep 7, 2016
@quentinmit quentinmit changed the title go/build: build.Import don't find vendored empty directory go/build: build.Import finds empty directories as packages Sep 7, 2016
@quentinmit
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I spoke to @rsc about this and it is WAI. build.Import finds empty directories because it might be used to figure out where a package "should" live (e.g. so that you can then place files in that directory). Whereas it does not find empty directories in vendor/ because they would shadow non-vendored non-empty directories. For example, if you vendor net/http/httptest, you will have an "empty" vendor/net/http directory (save the httptest subdirectory), and you do not want that empty vendor/net/http to replace the standard library's net/http.

Again, is there a particular place where you feel this logic breaks something?

@golang golang locked and limited conversation to collaborators Sep 12, 2017
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@quentinmit @Warashi @gopherbot