Test: Fix failfast for for loops (#58695)

Author: IanButterworth

stdlib/Test/src/Test.jl

@@ -1726,6 +1726,10 @@ end
 trigger_test_failure_break(@nospecialize(err)) =
     ccall(:jl_test_failure_breakpoint, Cvoid, (Any,), err)
 
+is_failfast_error(err::FailFastError) = true
+is_failfast_error(err::LoadError) = is_failfast_error(err.error) # handle `include` barrier
+is_failfast_error(err) = false
+
 """
 Generate the code for an `@testset` with a `let` argument.
 """
@@ -1837,7 +1841,7 @@ function testset_beginend_call(args, tests, source)
             # something in the test block threw an error. Count that as an
             # error in this test set
             trigger_test_failure_break(err)
-            if err isa FailFastError
+            if is_failfast_error(err)
                 get_testset_depth() > 1 ? rethrow() : failfast_print()
             else
                 record(ts, Error(:nontest_error, Expr(:tuple), err, Base.current_exceptions(), $(QuoteNode(source))))
@@ -1925,7 +1929,9 @@ function testset_forloop(args, testloop, source)
             # Something in the test block threw an error. Count that as an
             # error in this test set
             trigger_test_failure_break(err)
-            if !isa(err, FailFastError)
+            if is_failfast_error(err)
+                get_testset_depth() > 1 ? rethrow() : failfast_print()
+            else
                 record(ts, Error(:nontest_error, Expr(:tuple), err, Base.current_exceptions(), $(QuoteNode(source))))
             end
         end

stdlib/Test/test/runtests.jl

@@ -1394,7 +1394,7 @@ end
             @test occursin(expected, result)
         end
     end
-    @testset "failfast" begin
+    @testset "failfast begin-end" begin
         expected = r"""
         Test Summary: \| Fail  Total +Time
         Foo           \|    1      1  \s*\d*\.\ds
@@ -1419,6 +1419,32 @@ end
             @test occursin(expected, result)
         end
     end
+    @testset "failfast for-loop" begin
+        expected = r"""
+        Test Summary: \| Fail  Total +Time
+        Foo           \|    1      1  \s*\d*\.\ds
+          1           \|    1      1  \s*\d*\.\ds
+        """
+        mktemp() do f, _
+            write(f,
+            """
+            using Test
+
+            @testset "Foo" failfast=true begin
+                @testset "\$x" for x in 1:2
+                    @test false
+                end
+                @testset "Bar" begin
+                    @test false
+                    @test true
+                end
+            end
+            """)
+            cmd    = `$(Base.julia_cmd()) --startup-file=no --color=no $f`
+            result = read(pipeline(ignorestatus(cmd), stderr=devnull), String)
+            @test occursin(expected, result)
+        end
+    end
     @testset "failfast passes to child testsets" begin
         expected = r"""
         Test Summary: \| Fail  Total +Time