Call load_customisations! automatically, lazily

I've been wary about doing lazy application of load_customisations!, but
with the @noinline addition the calls are really cheap: only 1.5ns
according to Chairmarks on my machine. Thus, the cost of calling it
after initialisation will be negligeable for any non-trivial function.

Having rolled this around further, other than printing I think only
withfaces calls actually require loading of user styles to be valid.

With these two realisations, calling load_customisations! lazily as
appropriate seems like a bit of a no-brainer.

We'll probably want to add this to public API eventually for
non-text/html output implementations, but we can wait to see how this is
bourne out first.

src/StyledStrings.jl

@@ -25,19 +25,24 @@ Load customisations from the user's `faces.toml` file, if it exists as well as
 the current environment.
 
 This function should be called before producing any output in situations where
-the user's customisations should be considered.
+the user's customisations should be considered. This is called automatically
+when printing text or HTML output, and when calling `withfaces`, but may need
+to be called manually in unusual situations.
 
 Unless `force` is set, customisations are only applied when this function is
 called for the first time, and subsequent calls are a no-op.
 """
 function load_customisations!(; force::Bool=false)
     !force && HAVE_LOADED_CUSTOMISATIONS[] && return
-    if !isempty(DEPOT_PATH)
-        userfaces = joinpath(first(DEPOT_PATH), "config", "faces.toml")
-        isfile(userfaces) && loaduserfaces!(userfaces)
-    end
-    Legacy.load_env_colors!()
-    HAVE_LOADED_CUSTOMISATIONS[] = true
+    (function ()
+         @noinline
+         if !isempty(DEPOT_PATH)
+             userfaces = joinpath(first(DEPOT_PATH), "config", "faces.toml")
+             isfile(userfaces) && loaduserfaces!(userfaces)
+         end
+         Legacy.load_env_colors!()
+         HAVE_LOADED_CUSTOMISATIONS[] = true
+     end)()
     nothing
 end
 

src/faces.jl

@@ -465,6 +465,9 @@ red and blue mixed make purple
 ```
 """
 function withfaces(f, keyvals_itr)
+    # Before modifying the current `FACES`, we should ensure
+    # that we've loaded the user's customisations.
+    load_customisations!()
     if !(eltype(keyvals_itr) <: Pair{Symbol})
         throw(MethodError(withfaces, (f, keyvals_itr)))
     end

src/io.jl

@@ -227,6 +227,9 @@ end
 
 function _ansi_writer(io::IO, s::Union{<:AnnotatedString, SubString{<:AnnotatedString}},
                       string_writer::F) where {F <: Function}
+    # We need to make sure that the customisations are loaded
+    # before we start outputting any styled content.
+    load_customisations!()
     if get(io, :color, false)::Bool
         buf = IOBuffer() # Avoid the overhead in repeatadly printing to `stdout`
         lastface::Face = FACES.default[:default]
@@ -442,6 +445,9 @@ function htmlstyle(io::IO, face::Face, lastface::Face=getface())
 end
 
 function Base.show(io::IO, ::MIME"text/html", s::Union{<:AnnotatedString, SubString{<:AnnotatedString}})
+    # We need to make sure that the customisations are loaded
+    # before we start outputting any styled content.
+    load_customisations!()
     htmlescape(str) = replace(str, '&' => "&amp;", '<' => "&lt;", '>' => "&gt;")
     buf = IOBuffer() # Avoid potential overhead in repeatadly printing a more complex IO
     lastface::Face = getface()

src/precompile.jl

@@ -39,3 +39,5 @@ StyledStrings.resetfaces!()
 StyledStrings.withfaces(:yellow => StyledStrings.Face(foreground=:red), :green => :blue) do
     println(colorio, styled"{yellow:red} and {green:blue} mixed make {magenta:purple}")
 end
+
+StyledStrings.HAVE_LOADED_CUSTOMISATIONS[] = false