Add test to track how many times a patcher is run. Used to detect if …

…patching phases is erroneously applying the patcher multiple times.

test/patch/patch_count_test.go

@@ -0,0 +1,61 @@
+package patch_test
+
+import (
+	"testing"
+
+	"github.com/expr-lang/expr/internal/testify/require"
+
+	"github.com/expr-lang/expr"
+	"github.com/expr-lang/expr/ast"
+	"github.com/expr-lang/expr/test/mock"
+)
+
+// This patcher tracks how many nodes it patches which can 
+// be used to verify if it was run too many times or not at all
+type countingPatcher struct {
+	PatchCount int
+}
+
+func (c *countingPatcher) Visit(node *ast.Node) {
+	switch (*node).(type) {
+	case *ast.IntegerNode:
+		c.PatchCount++
+	}
+}
+
+// Test over a simple expression
+func TestPatch_Count(t *testing.T) {
+	patcher := countingPatcher{}
+
+	_, err := expr.Compile(
+		`5 + 5`,
+		expr.Env(mock.Env{}),
+		expr.Patch(&patcher),
+	)
+	require.NoError(t, err)
+
+	require.Equal(t, 2, patcher.PatchCount, "Patcher run an unexpected number of times during compile")
+}
+
+// Test with operator overloading
+func TestPatchOperator_Count(t *testing.T) {
+	patcher := countingPatcher{}
+
+	_, err := expr.Compile(
+		`5 + 5`,
+		expr.Env(mock.Env{}),
+		expr.Patch(&patcher),
+		expr.Operator("+", "_intAdd"),
+		expr.Function(
+			"_intAdd",
+			func(params ...any) (any, error) {
+				return params[0].(int) + params[1].(int), nil
+			},
+			new(func(int, int) int),
+		),
+	)
+
+	require.NoError(t, err)
+
+	require.Equal(t, 2, patcher.PatchCount, "Patcher run an unexpected number of times during compile")
+}