Add addenv(); a way to add new mappings into Cmd environment bloc…

…ks. (JuliaLang#37244)

NEWS.md

@@ -71,6 +71,7 @@ New library functions
  for writing `(f(args...) for args in zip(iterators...))`, i.e. a lazy `map` ([#34352]).
 * New function `sincospi` for simultaneously computing `sinpi(x)` and `cospi(x)` more
  efficiently ([#35816]).
+* New function `addenv` for adding environment mappings into a `Cmd` object, returning the new `Cmd` object.
 
 New library features
 --------------------

base/cmd.jl

@@ -60,9 +60,10 @@ while changing the settings of the optional keyword arguments:
  already open or on non-Windows systems.
 * `env`: Set environment variables to use when running the `Cmd`. `env` is either a
  dictionary mapping strings to strings, an array of strings of the form `"var=val"`, an
- array or tuple of `"var"=>val` pairs, or `nothing`. In order to modify (rather than
- replace) the existing environment, create `env` by `copy(ENV)` and then set
- `env["var"]=val` as desired.
+ array or tuple of `"var"=>val` pairs. In order to modify (rather than replace) the
+ existing environment, initialize `env` with `copy(ENV)` and then set `env["var"]=val` as
+ desired. To add to an environment block within a `Cmd` object without replacing all
+ elements, use `addenv()` which will return a `Cmd` object with the updated environment.
 * `dir::AbstractString`: Specify a working directory for the command (instead
  of the current directory).
 
@@ -230,10 +231,10 @@ byteenv(env::Union{AbstractVector{Pair{T,V}}, Tuple{Vararg{Pair{T,V}}}}) where {
  setenv(command::Cmd, env; dir="")
 
 Set environment variables to use when running the given `command`. `env` is either a
-dictionary mapping strings to strings, an array of strings of the form `"var=val"`, or zero
-or more `"var"=>val` pair arguments. In order to modify (rather than replace) the existing
-environment, create `env` by `copy(ENV)` and then setting `env["var"]=val` as desired, or
-use `withenv`.
+dictionary mapping strings to strings, an array of strings of the form `"var=val"`, or
+zero or more `"var"=>val` pair arguments. In order to modify (rather than replace) the
+existing environment, create `env` through `copy(ENV)` and then setting `env["var"]=val`
+as desired, or use `addenv`.
 
 The `dir` keyword argument can be used to specify a working directory for the command.
 """
@@ -242,6 +243,33 @@ setenv(cmd::Cmd, env::Pair{<:AbstractString}...; dir="") =
  setenv(cmd, env; dir=dir)
 setenv(cmd::Cmd; dir="") = Cmd(cmd; dir=dir)
 
+"""
+ addenv(command::Cmd, env...)
+
+Merge new environment mappings into the given `Cmd` object, returning a new `Cmd` object.
+Duplicate keys are replaced.
+"""
+function addenv(cmd::Cmd, env::Dict)
+ new_env = Dict{String,String}()
+ if cmd.env !== nothing
+ for (k, v) in split.(cmd.env, "=")
+ new_env[string(k)::String] = string(v)::String
+ end
+ end
+ for (k, v) in env
+ new_env[string(k)::String] = string(v)::String
+ end
+ return setenv(cmd, new_env)
+end
+
+function addenv(cmd::Cmd, pairs::Pair{<:AbstractString}...)
+ return addenv(cmd, Dict(k => v for (k, v) in pairs))
+end
+
+function addenv(cmd::Cmd, env::Vector{<:AbstractString})
+ return addenv(cmd, Dict(k => v for (k, v) in split.(env, "=")))
+end
+
 (&)(left::AbstractCmd, right::AbstractCmd) = AndCmds(left, right)
 redir_out(src::AbstractCmd, dest::AbstractCmd) = OrCmds(src, dest)
 redir_err(src::AbstractCmd, dest::AbstractCmd) = ErrOrCmds(src, dest)

base/exports.jl

@@ -914,6 +914,7 @@ export
  process_running,
  run,
  setenv,
+ addenv,
  success,
  withenv,
 

test/spawn.jl

@@ -700,6 +700,19 @@ end
 @test repr(Base.CmdRedirect(``, devnull, 11, true)) == "pipeline(``, 11<Base.DevNull())"
 
 
+# Issue #37070
+@testset "addenv()" begin
+ cmd = Cmd(`$shcmd -c "echo \$FOO \$BAR"`, env=Dict("FOO" => "foo"))
+ @test strip(String(read(cmd))) == "foo"
+ cmd = addenv(cmd, "BAR" => "bar")
+ @test strip(String(read(cmd))) == "foo bar"
+ cmd = addenv(cmd, Dict("FOO" => "bar"))
+ @test strip(String(read(cmd))) == "bar bar"
+ cmd = addenv(cmd, ["FOO=baz"])
+ @test strip(String(read(cmd))) == "baz bar"
+end
+
+
 # clean up busybox download
 if Sys.iswindows()
  rm(busybox, force=true)