create_foot can accept a tuple of one element. (@feet ) returns an em…

…pty vector of StockAndFlow0

src/Syntax.jl

@@ -951,8 +951,10 @@ Create a foot with S => N syntax, where S is stock, N is sum variable.
 ```
 """
 macro foot(block::Expr)
-    Base.remove_linenums!(block)
-    return create_foot(block)
+    escaped_block = Expr(:quote, block)
+    quote 
+        create_foot($(escaped_block))
+    end
 end
 
 
@@ -976,14 +978,23 @@ end
 """
 macro feet(block::Expr)
     Base.remove_linenums!(block)
-    @match block begin
-        quote
-          $((block...))
-        end => map(create_foot, block) # also matches empty
-        Expr(e, _...) => [create_foot(block)] # this also matches the above, so it's necessary this comes second.
+    escaped_block = Expr(:quote, block)
+    quote
+        inner_block = $escaped_block
+        @match inner_block begin
+            quote
+              $((inner_block...))
+            end => map(create_foot, inner_block) # also matches empty
+            Expr(e, _...) => [create_foot(inner_block)] # this also matches the above, so it's necessary this comes second.
+        end
     end
 end
 
+macro feet()
+    quote
+        Vector{StockAndFlow0}()
+    end
+end
 
 """
     create_foot(block :: Expr)
@@ -1004,10 +1015,9 @@ multiple_links = @foot A => B, A => B # will have two links from A to B.
 """
 function create_foot(block::Expr)
     @match block.head begin
-
         :tuple => begin
             if isempty(block.args) # case for create_foot(:())
-                error("Cannot create foot with no arguments.")
+                error("Cannot create foot with zero arguments.")
             end
             foot_s = Vector{Symbol}()
             foot_sv = Vector{Symbol}()

test/Syntax.jl

@@ -2,7 +2,7 @@ using Base: is_unary_and_binary_operator
 using Test
 using StockFlow
 using StockFlow.Syntax
-using StockFlow.Syntax: is_binop_or_unary, sum_variables, infix_expression_to_binops, fnone_value_or_vector, extract_function_name_and_args_expr, is_recursive_dyvar, create_foot, apply_flags, substitute_symbols
+using StockFlow.Syntax: is_binop_or_unary, sum_variables, infix_expression_to_binops, fnone_value_or_vector, extract_function_name_and_args_expr, is_recursive_dyvar, create_foot, apply_flags, substitute_symbols, DSLArgument
 
 @testset "Stratification DSL" begin
     include("syntax/Stratification.jl")
@@ -296,16 +296,14 @@ end
 end
 
 @testset "foot syntax disallows invalid feet" begin # note, @feet calls create_foot for each line, so this should apply to both @foot and @feet
-    @test_throws Exception create_foot(:(A => B => C)) # Invalid syntax for second argument of foot: B => C
-    @test_throws Exception create_foot(:(oooo2 + f => C)) # Invalid syntax for first argument of foot: oooo2 + f
-    @test_throws Exception create_foot(:(A + B)) # Invalid syntax function for foot: +
-    @test_throws Exception create_foot(:(=>)) # no method matching create_foot(::Symbol)
-    @test_throws Exception create_foot(:(=>(A, B, C, D)))
-    @test_throws Exception create_foot(:())
-    @test_throws Exception create_foot(:(([]) => ()))
-
-    @test_throws Exception create_foot(:(A => B, P => Q, C))
-    @test_throws Exception create_foot(:(() => E, () => (K,)))
+    @test_throws ErrorException @foot A => B => C # Invalid syntax for second argument of foot: B => C
+    @test_throws ErrorException @foot oooo2 + f => C # Invalid syntax for first argument of foot: oooo2 + f
+    @test_throws ErrorException @foot A + B # Invalid syntax function for foot: +
+    @test_throws ErrorException @foot =>(A, B, C, D)
+    @test_throws ErrorException @foot ()
+    @test_throws ErrorException @foot ([]) => ()
+    @test_throws MethodError @foot A => B, P => Q, C # Issue here is it tries calling match_foot_format with a symbol
+    @test_throws ErrorException @foot () => E, () => (K,)
 
 end
 
@@ -344,12 +342,13 @@ end
         foot(:J, (:K, :Q), (:J => :K, :J => :Q))
     ]
 
+    @test (@feet ) == Vector{StockAndFlow0}();
 end
 
 @testset "feet syntax fails on invalid feet" begin # mostly to check that an exception is thrown even if some of the feet are valid.
-    @test_throws Exception @eval @feet A => B => C # eval required so the errors occur at runtime, rather than at compilation
-    @test_throws Exception @eval @feet begin A => B; =>(D,E,F) end
-    @test_throws Exception @eval @feet begin A => B; 1 => 2; end
+    @test_throws ErrorException @feet A => B => C 
+    @test_throws ErrorException @feet begin A => B; =>(D,E,F) end
+    @test_throws ErrorException @feet begin A => B; 1 => 2; end
 end
 
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