Parse package build flags

[andig]

Follow-up to #21 which added per-package build args. Unfortunately the implementation did not work as the flags passed to go build where- while not causing an error- effectively not applied.

This PR fixes that by parsing the build flags early and using the parsed flags. go.mod/sum are cleaned.

[stapelberg]

Wouldn’t it also work to put one parameter per line into the file? I’m a bit hesitant to pull shell semantics into the mix.

[andig]

Wouldn’t it also work to put one parameter per line into the file? I’m a bit hesitant to pull shell semantics into the mix.

Only if we enforce parsing the per-line syntax (currently not the case). It does not feel obvious to do that and is a bit more cumbersome creating these files e.g. from Makefile. breakglass was already using shlex so it felt the right thing to do.

I would appreciate if the obvious thing- make single-line expressions work- and shlex performed well in my test.

[stapelberg]

Only if we enforce parsing the per-line syntax (currently not the case)

How do you mean? Can you show an example?

breakglass was already using shlex so it felt the right thing to do

breakglass has no other choice because of how SSH works.

Here, we have a choice, and shell escaping/splitting does not classify as “obvious” to me, so let’s think about this a little :)

[andig]

How do you mean? Can you show an example?

Right now the entire buildflags.txt is passed as blob to the args. We're not doing line-splitting (i.e. I didn't notice this needed be done).

Here, we have a choice, and shell escaping/splitting does not classify as “obvious” to me, so let’s think about this a little :)

Absolutely. I've tested the following:

BUILD_ARGS := -tags='release gokrazy' -ldflags '-X "github.com/andig/evcc/server.Version=$(VERSION)" -X "github.com/andig/evcc/server.Commit=$(SHA)"'

mkdir -p buildflags/github.com/andig/evcc
echo "$(BUILD_ARGS)" > buildflags/github.com/andig/evcc/buildflags.txt

[stapelberg]

Right now the entire buildflags.txt is passed as blob to the args. We're not doing line-splitting (i.e. I didn't notice this needed be done).

Ah, I missed that part part about line splitting during code review :)

BUILD_ARGS := -tags='release gokrazy' -ldflags '-X "github.com/andig/evcc/server.Version=$(VERSION)" -X "github.com/andig/evcc/server.Commit=$(SHA)"'

So if we did line splitting, this would be:

-tags=release gokrazy
-ldflags=-X github.com/andig/evcc/server.Version=$(VERSION) -X github.com/andig/evcc/server.Commit=$(SHA)

If you were to specify these to go build on the shell for testing, you can just quote the entire line:

go build "-ldflags=-X main.Version=bleh -X main.Commit=foo" inject.go && ./inject 

What benefit would shlex give us over the string splitting method?

[andig]

How about this:

    var buildFlags []string
    sc := bufio.NewScanner(strings.NewReader(string(b)))
    for sc.Scan() {
        if flag := strings.TrimSpace(sc.Text()); flag != "" {
            buildFlags = append(buildFlags, flag)
        }
    }

[andig]

Ping @stapelberg better now with build flags per line?