5 files changed, 51 insertions, 10 deletions
diff --git a/atk16_asm/asm_pass0.py b/atk16_asm/asm_pass0.py
index bda16a4..35bfff2 100644
--- a/atk16_asm/asm_pass0.py
+++ b/atk16_asm/asm_pass0.py
@@ -16,10 +16,15 @@ class Result0:
   lines: list[Result0Line]
 
 InsertAtDataSegment = Callable[[str, list[str], str, int], None]
+IncludeModule = Callable[[str], None]
+
+def pass_0(lines: list[str], file_name: str,
+           insert_at_data_segment: InsertAtDataSegment | None = None,
+           include_module: IncludeModule | None = None) -> Result0:
 
-def pass_0(lines: list[str], file_name: str, insert_at_data_segment: InsertAtDataSegment | None = None) -> Result0:
   file_name = file_name if file_name.endswith(".atk16") else file_name + ".atk16"
   result_lines: list[Result0Line] = []
+  included_module_abs_paths: list[str] = []
 
   if not insert_at_data_segment:
     def _insert_at_data_segment(label: str, values: list[str], context_file_name: str, context_line_num: int):
@@ -71,6 +76,26 @@ def pass_0(lines: list[str], file_name: str, insert_at_data_segment: InsertAtDat
 
     insert_at_data_segment = _insert_at_data_segment
 
+  if not include_module:
+    def _include_module(module_abs_path: str):
+      if module_abs_path in included_module_abs_paths:
+        return
+
+      with open(module_abs_path, "r") as f:
+        incl_lines = f.readlines()
+
+      incl_result0 = pass_0(incl_lines, asm_file_name, insert_at_data_segment)
+      for incl_line in incl_result0.lines:
+        result_lines.append(Result0Line(
+          src_file=incl_line.src_file,
+          line_num=incl_line.line_num,
+          line=incl_line.line
+        ))
+
+      included_module_abs_paths.append(module_abs_path)
+
+    include_module = _include_module
+
   for (line_num, line) in enumerate(lines):
     line_num += 1 # line numbers are 1-based
 
@@ -106,16 +131,8 @@ def pass_0(lines: list[str], file_name: str, insert_at_data_segment: InsertAtDat
           path = asm_file_name
         else:
           path = os.path.join(os.path.dirname(file_name), asm_file_name)
-        with open(path, "r") as f:
-          incl_lines = f.readlines()
 
-        incl_result0 = pass_0(incl_lines, asm_file_name, insert_at_data_segment)
-        for incl_line in incl_result0.lines:
-          result_lines.append(Result0Line(
-            src_file=incl_line.src_file,
-            line_num=incl_line.line_num,
-            line=incl_line.line
-          ))
+        include_module(path)
 
       case _:
         result_lines.append(Result0Line(
diff --git a/atk16_ast_walking_compiler/sample_py/test_py_src.py b/atk16_ast_walking_compiler/sample_py/sample_py_src.py
index 619d22e..619d22e 100644
--- a/atk16_ast_walking_compiler/sample_py/test_py_src.py
+++ b/atk16_ast_walking_compiler/sample_py/sample_py_src.py
diff --git a/test/e2e/include_idempotency/p1.atk16 b/test/e2e/include_idempotency/p1.atk16
new file mode 100644
index 0000000..f9f6363
--- /dev/null
+++ b/test/e2e/include_idempotency/p1.atk16
@@ -0,0 +1,4 @@
+@include %bootstrap
+
+@label main
+  hlt
diff --git a/test/e2e/include_idempotency/p2.atk16 b/test/e2e/include_idempotency/p2.atk16
new file mode 100644
index 0000000..c6d46b9
--- /dev/null
+++ b/test/e2e/include_idempotency/p2.atk16
@@ -0,0 +1,6 @@
+@include %bootstrap
+@include %bootstrap
+@include %bootstrap
+
+@label main
+  hlt
diff --git a/test/e2e/include_idempotency/test_include_idempotent.py b/test/e2e/include_idempotency/test_include_idempotent.py
new file mode 100644
index 0000000..e7b4fc8
--- /dev/null
+++ b/test/e2e/include_idempotency/test_include_idempotent.py
@@ -0,0 +1,14 @@
+import os.path
+from test.utils import assemble_and_run_until_halted
+
+def test_include_idempotent():
+  machine1 = assemble_and_run_until_halted(
+    os.path.join(os.path.dirname(__file__), "p1.atk16")
+  )
+
+  machine2 = assemble_and_run_until_halted(
+    os.path.join(os.path.dirname(__file__), "p2.atk16")
+  )
+
+  for i in range(len(machine1.rom.memory)):
+    assert machine1.rom.memory[i] == machine2.rom.memory[i]