Fix spaces around assignment in for-loop specifications

`for`-loop nodes are of kind K"=" even when using `in`. This patch fixes
the predicate for `spaces_around_assignments` to include K"in" as an
option. Note that when using `in` spaces are required, but the pass
is still useful to remove spaces when there are more than one.

src/runestone.jl

@@ -283,5 +283,8 @@ function spaces_around_assignments(ctx::Context, node::JuliaSyntax.GreenNode)
     if !(is_assignment(node) && !JuliaSyntax.is_trivia(node))
         return nothing
     end
-    return spaces_around_x(ctx, node, is_assignment)
+    # for-loop nodes are of kind K"=" even when `in` is used so we need to
+    # include K"in" in the predicate too.
+    is_x = x -> is_assignment(x) || JuliaSyntax.kind(x) === K"in"
+    return spaces_around_x(ctx, node, is_x)
 end

test/runtests.jl

@@ -136,4 +136,9 @@ end
     @test format_string("a =+ c") == "a = + c"
     # Short form function definitions
     @test format_string("sin(π)=cos(pi)") == "sin(π) = cos(pi)"
+    # For loop nodes are assignment, even when using `in`
+    @test format_string("for i=1:10\nend\n") == "for i = 1 : 10\nend\n"
+    @test format_string("for i  =1:10\nend\n") == "for i = 1 : 10\nend\n"
+    @test format_string("for i  =  1:10\nend\n") == "for i = 1 : 10\nend\n"
+    @test format_string("for i  in  1:10\nend\n") == "for i in 1 : 10\nend\n"
 end