Fix lack of color in CI and don't warn about loaded packages in test Pkg.precompile. (#4316)

Author: IanButterworth

src/API.jl

@@ -1172,10 +1172,12 @@ function precompile(ctx::Context, pkgs::Vector{PackageSpec}; internal_call::Bool
     end
 
     io = ctx.io
-    if io isa IOContext{IO}
+    if io isa IOContext{IO} && !isa(io.io, Base.PipeEndpoint)
         # precompile does quite a bit of output and using the IOContext{IO} can cause
         # some slowdowns, the important part here is to not specialize the whole
-        # precompile function on the io
+        # precompile function on the io.
+        # But don't unwrap the IOContext if it is a PipeEndpoint, as that would
+        # cause the output to lose color.
         io = io.io
     end
 

src/Operations.jl

@@ -2476,7 +2476,9 @@ function test(ctx::Context, pkgs::Vector{PackageSpec};
 
             if should_autoprecompile()
                 cacheflags = Base.CacheFlags(parse(UInt8, read(`$(Base.julia_cmd()) $(flags) --eval 'show(ccall(:jl_cache_flags, UInt8, ()))'`, String)))
-                Pkg.precompile(; io=ctx.io, configs = flags => cacheflags)
+                # Don't warn about already loaded packages, since we are going to run tests in a new
+                # subprocess anyway.
+                Pkg.precompile(; io=ctx.io, warn_loaded = false, configs = flags => cacheflags)
             end
 
             printpkgstyle(ctx.io, :Testing, "Running tests...")