CODEWITHSUNDEEP
gogo-modulesgovendor
mic4ael
mic4ael

Reputation: 8310

Import provided by both the main module and the vendor directory is flagged as an error

I would like to understand the reason for the error I have experienced while brushing up on go modules & the vendor directory. Apparently, having the same package in the main module and the vendor folder results in an error and I would like to understand why. As far as I understand, if there is a go.mod go shouldn't even check the vendor folder for dependencies. Once I run go run ./main.go I get the following error:

main.go:3:8: ambiguous import: found package test/testpkg in multiple directories:
        /Users/mic4ael/dev/mine/something-in-go/testpkg
        /Users/mic4ael/dev/mine/something-in-go/vendor/test/testpkg

However, this doesn't happen when go build -mod=mod is used to build a binary. I would appreciate explanation why this is the case.

GO111MODULE=""

$ tree
.
├── go.mod
├── main.go
├── test
├── testpkg
│   └── lib.go
└── vendor
    └── test
        └── testpkg
            └── lib.go

go.mod

module test

go 1.15

main.go

package main

import "test/testpkg"

func main() {
    testpkg.Echo("Test")
}

vendor/test/testpkg/lib.go

package testpkg

import "fmt"

func Echo(str string) {
    fmt.Printf("From vendored package %s\n", str)
}

testpkg/lib.go

package testpkg

import "fmt"

func Echo(str string) {
    fmt.Printf("From internal pkg: %s\n", str)
}

Upvotes: 0

Views: 739

Answers (1)

Burak Serdar
Burak Serdar

Reputation: 51582

There are two packages with the same name, and that is the ambiguity. When you import test/testpkg it can be imported from the project itself or from the vendor directory.

Using go modules does not change the vendoring behavior. In fact, you can use go mod vendor to vendor modules locally. If a package appears under vendor/ it will be used from the vendored copy, otherwise it will be downloaded and used from the module cache. However, if you have a package in your project with the identical name as one of the packages under vendor, there is an ambiguity.

Upvotes: 2

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