插件和主应用之间的Golang软件包版本

Question

I'm not a Go expert, so I may be doing this in a way that is not the ideal approach for Go. Essentially, I have a main application that needs to be able to have plugins written for it. The plugins all adhere to a given format and are built with go build -buildmode=plugin. I don't want the end user to need to recompile the main application every time. Ideally, you should be able to drag and drop it to a new computer without issue.

To pass information between the plugins and the application, I have a third package defined called "common" that I treat similar to a C-header file. It only defines interfaces and a few integer constants that both can use. The application generates types that adhere to the interface and can pass them to the plugins to use.

When I compile, it seems to work fine, and the application can load the plugins using plugin.Open. The catch comes when trying to move the location of the common package. I built the original application in a local directory and I have a script that installs the application and the copies the common package into the GOPATH so that it can be found. Now, when I try to create plugins and compile them referencing the global copy of the common package, I can't load them in the main application because it sees the two occurrences of the package as being different versions.

My understanding is that to determine package version, a hash is made of all the Go files in the package at compile time. Is this hash including the location on the server where the package was found as well?

I know for a fact that the actual versions of the packages are identical. The only different is that I did cp -r src/myapp /usr/local/go/src. Is there a better way to accomplish this than my approach that still allows the user to move the main application around to different machines and not need to recompile it?

Further explanation:

Here is my directory structure

./
   |-- main.go 
   |-- src/myapp/common
   |      |-- Common.go
   |-- install.sh

Once I compile this into myapp, I copy src/myapp/common into the GOPATH and then build plugins with go build -buildmode=plugin against that package. When loading those plugins from myapp, it sees the two versions of myapp/common as being different, although the only difference is location on the server.

Answer 1

Have you tried instead keeping the path of the common package stable? You should probably have that in its own repo (so that both projects can refer to it), or keep it in your app repo, but allow plugins to link to it there.

So for example say your project lives at:

github.com/brianwest/myapp

you could make the import path (for both app and plugins):

github.com/brianwest/myapp/src/common

OR

github.com/brianwest/common

and keep it stable across the app and plugins, then it should just work and you won't need the script to copy it into gopath, or if you do it can put it at src/github.com/brianwest/common and use that path in both plugins and your app.