make clean does not enable rebuild of geth

[hqueue]

System information

Geth version: 1.8.12-unstable
Go Version: go1.10.3
OS & Version: OSX
Commit hash : b0cfd9c

Expected behaviour

make geth should rebuild source code after make clean

Actual behaviour

make clean does not enable full rebuild of go-ethereum as below when using go version 1.10 or later.

$ make geth
build/env.sh go run build/ci.go install ./cmd/geth
>>> /usr/local/go/bin/go install -ldflags -X main.gitCommit=0a22ae55729298dcd9979184d0b3c28f48b272bf -s -v ./cmd/geth
Done building.
Run "/Users/hqueue/work/go-ethereum/build/bin/geth" to launch geth.

Steps to reproduce the behaviour

1. Install go with version 1.10 or higher.

2. git clone go-ethereum

3. make geth This will trigger the first time full build of geth

4. make clean

5. make geth does not rebuild geth, just install it as below

$ make geth
build/env.sh go run build/ci.go install ./cmd/geth
>>> /usr/local/go/bin/go install -ldflags -X main.gitCommit=0a22ae55729298dcd9979184d0b3c28f48b272bf -s -v ./cmd/geth
Done building.
Run "/Users/hqueue/work/go-ethereum/build/bin/geth" to launch geth.
$

Backtrace

go build make use of cache from 1.10 (see https://golang.org/doc/go1.10#build) and go does not rebuild source code if there is no change.

We have to clean go build cache using go clean -cache.

$ go clean -cache
$ make geth  // Now it will rebuild code

A PR will be filed to perform go clean -cache when we trigger make clean.

[karalabe]

But why would you want to do a full rebuild? Go uses hashes of the source files to detect whether something changed or not, so doing a full rebuild shouldn't be something too useful. Am I missing something here?

[hqueue]

But why would you want to do a full rebuild? Go uses hashes of the source files to detect whether something changed or not, so doing a full rebuild shouldn't be something too useful. Am I missing something here?

@karalabe Right in normal cases.
However if a developer used make clean explicitly, then I think the developer may want to trigger a clean full build of go-ethereum for some reason. What do you think of it ?

[karalabe]

Cleaning Go's cache will clean out everything, not just go-ethereum related things. As for forcing a rebuild, why is that good? Any change + Go version change will rebuild everything anyway. Feels like a hack to mimic some legacy behavior originating from C++ which was not always able to detect changes properly.

[hqueue]

Cleaning Go's cache will clean out everything, not just go-ethereum related things

Right. This is one (critical) downside of using go clean -cache.

As for forcing a rebuild, why is that good? Any change + Go version change will rebuild everything anyway. Feels like a hack to mimic some legacy behavior originating from C++ which was not always able to detect changes properly.

Agree :) If go develpers don't care about this issue, we can just close this issue.

Frankly speaking, I'm still more get used to legacy behavior of C++ make system, that's one reason I raised this issue.

Thanks for sharing your opinion on this cleaning issue :)

I will close this issue and related PR soon, if there is no more discussion.