Try fixing the non-stdlib tests via refactor

In JuliaLang/julia#53922 it was revealed that
simply gating the supposition-requiring test behind an if statement was
insufficient when a macro is involved in the branch not taken.

To try to make this approach work, the current conditional
fuzzer-running code was refactored to make the the macro and other code
requiring Supposition be nicely contained in a file that's only loaded
when NON_STDLIB_TESTS is true. Put another way, we've hoisted the
conditional running from an "is the code run?" if-branch to a
file-loading if-branch.

Author: tecosaur

test/runtests.jl

@@ -7,7 +7,12 @@ using StyledStrings: StyledStrings, Legacy, SimpleColor, FACES, Face,
 using .StyledMarkup: MalformedStylingMacro
 using Base: AnnotatedString, AnnotatedChar, AnnotatedIOBuffer, annotations
 
-include("maybefuzz.jl") # For use in the "Styled Markup" testset
+const NON_STDLIB_TESTS = Main == @__MODULE__
+if NON_STDLIB_TESTS
+    include("styfuzz.jl") # For use in the "Styled Markup" testset
+else
+    styfuzz() = nothing
+end
 
 # For output testing
 
@@ -424,7 +429,7 @@ end
 end
 
 # Markup fuzzing!
-maybefuzz()
+styfuzz()
 
 @testset "AnnotatedIOBuffer" begin
     aio = AnnotatedIOBuffer()

test/maybefuzz.jl renamed to test/styfuzz.jl

@@ -1,6 +1,6 @@
 # This file is a part of Julia. License is MIT: https://julialang.org/license
 
-const NON_STDLIB_TESTS = Main == @__MODULE__
+# *Not* run as part of the Julia central stdlib testsuite
 
 const IS_CI = lowercase(get(ENV, "CI", "no")) in ("true", "t", "1", "yes", "y")
 const PARSER_FILE = joinpath("src", "styledmarkup.jl")
@@ -22,24 +22,18 @@ function hasparserdiverged()
     !success(Cmd(`git diff --quiet --diff-filter=M $upstream -- $PARSER_FILE`, dir=PROJECT_DIR))
 end
 
-if NON_STDLIB_TESTS
-    using Supposition
-    include("fuzz.jl")
-    using .Fuzzer
-end
+using Supposition
+include("fuzz.jl")
+using .Fuzzer
 
-if NON_STDLIB_TESTS
-    function maybefuzz()
-        isstyled(s) = StyledStrings.styled(s) isa Base.AnnotatedString
-        max_examples = if hasparserdiverged()
-            ifelse(IS_CI, 5_000, 10_000)
-        else
-            1_000
-        end
-        @testset "Fuzz ($max_examples)" begin
-            @check max_examples = max_examples isstyled(Fuzzer.content)
-        end
+function styfuzz()
+    isstyled(s) = StyledStrings.styled(s) isa Base.AnnotatedString
+    max_examples = if hasparserdiverged()
+        ifelse(IS_CI, 5_000, 10_000)
+    else
+        1_000
+    end
+    @testset "Fuzz ($max_examples)" begin
+        @check max_examples = max_examples isstyled(Fuzzer.content)
     end
-else
-    maybefuzz() = nothing
 end