On Wednesday, 13 March 2013 at 20:44:00 UTC, Lars T. Kyllingstad
wrote:
On Wednesday, 13 March 2013 at 20:26:44 UTC, Steven
Schveighoffer wrote:
I hate to have feature creep at this point, but one kind of
annoying thing
is, if you want to *add* to the current environment, it is a
multi-step
process:
auto curenv = environment.toAA;
curenv["x"] = "y";
spawnProcess("helloworld", curenv);
But with something similar to Dennis' idea, we have a possible
way to do
that without making a copy of the current environment into an
AA and
adding:
struct EnvironmentArg
{
this(string[string] env, bool useParent=false) { this.env
= env;
this.useParent = useParent;}
this(bool useParent) {this.useParent = useParent;}
string[string] env;
bool useParent;
}
spawnProcess("helloworld", EnvironmentArg(["x":"y"], true));
// use parent
environment, add x=y
spawnProcess("helloworld", EnvironmentArg(["x":"y"])); //
replace
environment with x=y
spawnProcess("helloworld", EnvironmentArg(false)); // use
empty environment
spawnProcess("helloworld", EnvironmentArg(true)); // use parent
environment exactly
EnvironmentArg should probably have better name, and I would
recommend
some global functions that make common things, like:
EnvironmentArg emptyEnvironment() { return
EnvironmentArg(null, false);}
EnvironmentArg parentEnvironment() { return
EnvironmentArg(null, true);}
Like? Hate?
Hmm.. what if spawnProcess() takes a normal string[string] like
it does now, but we add a flag to Config that determines
whether it is merged with the parent's environment or not?
string[string] myEnv = [ "foo" : "bar" ];
spawnProcess("helloworld", null); // Parent's env
spawnProcess("helloworld", myEnv); // Parent's env + myEnv
spawnProcess("helloworld", null, ..., Config.clearEnv); //
Empty env
spawnProcess("helloworld", myEnv, ..., Config.clearEnv); //
Only myEnv
The more I think about this, the more it seems like a good idea:
1. A string[string] parameter for the environment, which defaults
to null, and for which there is no difference between null and
empty -- they are both empty.
2. A Config flag that determines whether the given AA should be
merged with the parent's environment or not, with the former
being the default.
3. Variables in the AA always override variables from the
parent's environment.
4. The two spawnProcess() overloads that do *not* take an
environment parameter will be removed.
5. Instead, we add two overloads without the redirection
parameters, since the Config parameter will probably be used more
often now:
spawnProcess(string prog, string[string] env, Config conf);
spawnProcess(string[] args, string[string] env, Config conf);
Looks good?
Lars
