More predictible parsing with escape_raw_string

Due to the initial parsing of the string before the macro sees it,
followed by the use of `unescape_string`, you currently need to double
up trailing backslashes. We can fix this by calling escape_raw_string in
advance.

This change may cause undesirable side-effects with less comply used
macro forms (e.g. `@styled_str "\\"`), but we'll deal with that if and
when it comes up.

src/stylemacro.jl

@@ -84,9 +84,11 @@ inheritval = whitespace, ':'?, symbol ;
 ```
 """
 macro styled_str(raw_content::String)
-    #------------------
-    # Helper functions
-    #------------------
+    # First undo the transforms of the parser, (assuming the input was entered
+    # with single `styled""` markers so this transform is unambiguously
+    # reversible and not as `@styled_str "."` or `styled"""."""`), since the
+    # `unescape_string` transforms will be a superset of those transforms
+    raw_content = Base.escape_raw_string(raw_content)
 
     # If this were a module, I'd define the following struct.
 
@@ -128,6 +130,10 @@ macro styled_str(raw_content::String)
          "grey", "gray", "bright_black", "bright_red", "bright_green", "bright_yellow",
          "bright_blue", "bright_magenta", "bright_cyan", "bright_white")
 
+    #------------------
+    # Helper functions
+    #------------------
+
     function styerr!(state, message, position::Union{Nothing, Int}=nothing, hint::String="around here")
         if !isnothing(position) && position < 0
             position = prevind(

test/runtests.jl

@@ -207,6 +207,14 @@ end
             @macroexpand styled"{(foreground=$color):val}"
     end
 
+    # Trailing (and non-trailing) Backslashes
+    @test String(styled"\\") == "\\"
+    @test String(styled"\\\\") == "\\\\"
+    @test String(styled"\\\\\\") == "\\\\\\"
+    @test String(styled".\\") == ".\\"
+    @test String(styled".\\\\") == ".\\\\"
+    @test String(styled".\\\\\\") == ".\\\\\\"
+
     # newlines
     normal = "abc\
               def"