Environment copied before being mutated

[lionello]

This line initializes the Environment, when not initialized by the caller:

compose-go/loader/loader.go

Line 269 in 8585af8

configDetails.Environment = map[string]string{}

But the environment gets copied (implicitly) earlier on this line:

compose-go/loader/loader.go

Line 249 in 8585af8

LookupValue: configDetails.LookupEnv,

So, when Environment is nil, the set of COMPOSE_PROJECT_NAME in the map is not visible by the call to LookupValue.

A potential fix is to change func (cd ConfigDetails) LookupEnv(…) to a pointer receiver to avoid the copy.

[ndeloof]

afaict, LookupValue: configDetails.LookupEnv captures LookupEnv func with configDetails receiver. Later configDetails.Environment value is set, this doesn't change reference to configDetails used as receiver and as such execution of this func will use this map. But maybe I'm wrong with actual reference in use.

Do you have an explicit scenario which demonstrates such an issue ?

[lionello]

That's correct, but only if it's not nil to begin with. If initialized to a new map, all's good and the project name is being picked up (even though it's added after the capture), but if it's nil, then the project name is added to the new map, but the captured value is still nil.

[ndeloof]

I don't get it. we capture LookupEnv func, so actually the configDetails receiver, then when executed this function will access receiver field Environment, even this one was set after.
Please provide an illustration example (either code or docker compose usage) to demonstrate a bug