fix(build): Fix module changes not getting picked up

Previously, we left out the dependency of the QSTR header on modules.h. This was done to prevent rebuilds of the entire MicroPython sources whenever a Pycardium module is changed. This leads to issues where QSTRs got out of sync and weird errors like the following could happen:

import foo_module

Exception: No module `abc_def` (a different string than expected)

Attempt to fix this by only updating the QSTR header when the module-header actually changes. For this, a few workarounds are needed:

• Replace symlinks with actual copied files so timestamps change on updates.
• Add a hack so meson picks up on the dependency of the file in genhdr/

Co-authored-by: dx dequis@dequis.org

---

@schneider: Please test whether this works on your system as well ;)

lib/micropython/gen-modules.py

@@ -3,6 +3,8 @@
 
 import sys
 import os
+import tempfile
+import shutil
 
 
 def main():
@@ -16,23 +18,41 @@ def main():
         modules |= makemoduledefs.find_module_registrations(source)
 
     stdout = sys.stdout
-    with open(sys.argv[2], "w") as f:
-        sys.stdout = f
+    with tempfile.TemporaryFile("w+") as temp:
+        sys.stdout = temp
         makemoduledefs.generate_module_table_header(sorted(modules))
-    sys.stdout = stdout
+        sys.stdout = stdout
+
+        # Read contents of existing file and compare
+        try:
+            with open(sys.argv[2], "r") as f:
+                old_content = f.read()
+        except FileNotFoundError:
+            old_content = ""
+
+        temp.seek(0)
+        new_content = temp.read()
+
+        if new_content == old_content:
+            # If both file contain the same content, exit early
+            sys.exit(0)
 
-    try:
-        os.mkdir(os.path.dirname(sys.argv[2]) + "/genhdr")
-    except FileExistsError:
-        pass
-
-    linkname = os.path.dirname(sys.argv[2]) + "/genhdr/" + os.path.basename(sys.argv[2])
-    if os.path.exists(linkname):
-        os.unlink(linkname)
-    os.symlink(
-        "../" + os.path.basename(sys.argv[2]),
-        linkname,
-    )
+        with open(sys.argv[2], "w") as f:
+            f.write(new_content)
+
+        try:
+            os.mkdir(os.path.dirname(sys.argv[2]) + "/genhdr")
+        except FileExistsError:
+            pass
+
+        linkname = (
+            os.path.dirname(sys.argv[2]) + "/genhdr/" + os.path.basename(sys.argv[2])
+        )
+        if os.path.exists(linkname):
+            os.unlink(linkname)
+        shutil.copy(sys.argv[2], linkname)
+
+    sys.stdout = stdout
 
 
 if __name__ == "__main__":