fix: Ignore .aws-sam in sam build cache checksum

samcli/lib/build/build_strategy.py

@@ -214,7 +214,7 @@ def build_single_function_definition(self, build_definition: FunctionBuildDefini
             return self._delegate_build_strategy.build_single_function_definition(build_definition)
 
         code_dir = str(pathlib.Path(self._base_dir, cast(str, build_definition.codeuri)).resolve())
-        source_md5 = dir_checksum(code_dir)
+        source_md5 = dir_checksum(code_dir, ignore_list=[".aws-sam"])
         cache_function_dir = pathlib.Path(self._cache_dir, build_definition.uuid)
         function_build_results = {}
 
@@ -253,7 +253,7 @@ def build_single_layer_definition(self, layer_definition: LayerBuildDefinition)
         Builds single layer definition with caching
         """
         code_dir = str(pathlib.Path(self._base_dir, cast(str, layer_definition.codeuri)).resolve())
-        source_md5 = dir_checksum(code_dir)
+        source_md5 = dir_checksum(code_dir, ignore_list=[".aws-sam"])
         cache_function_dir = pathlib.Path(self._cache_dir, layer_definition.uuid)
         layer_build_result = {}
 

samcli/lib/utils/hash.py

@@ -3,6 +3,7 @@
 """
 import os
 import hashlib
+from typing import List, Optional
 
 BLOCK_SIZE = 4096
 
@@ -37,25 +38,32 @@ def file_checksum(file_name: str) -> str:
         return md5.hexdigest()
 
 
-def dir_checksum(directory: str, followlinks: bool = True) -> str:
+def dir_checksum(directory: str, followlinks: bool = True, ignore_list: Optional[List[str]] = None) -> str:
     """
 
     Parameters
     ----------
     directory : A directory with an absolute path
     followlinks: Follow symbolic links through the given directory
+    ignore_list: The list of file/directory names to ignore in checksum
 
     Returns
     -------
     md5 checksum of the directory.
 
     """
+    ignore_set = set(ignore_list or [])
     md5_dir = hashlib.md5()
     files = list()
     # Walk through given directory and find all directories and files.
-    for dirpath, _, filenames in os.walk(directory, followlinks=followlinks):
+    for dirpath, dirnames, filenames in os.walk(directory, followlinks=followlinks):
+        # > When topdown is True, the caller can modify the dirnames list in-place
+        # > (perhaps using del or slice assignment) and walk() will only recurse
+        # > into the subdirectories whose names remain in dirnames
+        # > https://docs.python.org/library/os.html#os.walk
+        dirnames[:] = [dirname for dirname in dirnames if dirname not in ignore_set]
         # Go through every file in the directory and sub-directory.
-        for filepath in [os.path.join(dirpath, filename) for filename in filenames]:
+        for filepath in [os.path.join(dirpath, filename) for filename in filenames if filename not in ignore_set]:
             # Look at filename and contents.
             # Encode file's checksum to be utf-8 and bytes.
             files.append(filepath)

tests/unit/lib/utils/test_hash.py

@@ -40,11 +40,11 @@ def test_dir_hash_independent_of_file_order(self):
             mockwalk.return_value = [
                 (
                     self.temp_dir,
-                    (),
-                    (
+                    [],
+                    [
                         file1.name,
                         file2.name,
-                    ),
+                    ],
                 ),
             ]
             dir_checksums["first"] = dir_checksum(self.temp_dir)
@@ -53,11 +53,11 @@ def test_dir_hash_independent_of_file_order(self):
             mockwalk.return_value = [
                 (
                     self.temp_dir,
-                    (),
-                    (
+                    [],
+                    [
                         file2.name,
                         file1.name,
-                    ),
+                    ],
                 ),
             ]
             dir_checksums["second"] = dir_checksum(self.temp_dir)
@@ -73,6 +73,27 @@ def test_dir_hash_same_contents_diff_file_per_directory(self):
         checksum_after = dir_checksum(os.path.dirname(_file.name))
         self.assertNotEqual(checksum_before, checksum_after)
 
+    def test_dir_hash_with_ignore_list(self):
+        _file = tempfile.NamedTemporaryFile(delete=False, dir=self.temp_dir)
+        _file.write(b"Testfile")
+        _file.close()
+
+        dir_path = os.path.dirname(_file.name)
+        checksum_before = dir_checksum(dir_path)
+
+        # add a file to .aws-sam/
+        aws_sam_dir_path = os.path.join(dir_path, ".aws-sam")
+        os.mkdir(aws_sam_dir_path)
+        _new_file = tempfile.NamedTemporaryFile(delete=False, dir=aws_sam_dir_path)
+        _new_file.write(b"dummy")
+        _new_file.close()
+
+        checksum_after = dir_checksum(os.path.dirname(_file.name))
+        self.assertNotEqual(checksum_before, checksum_after)
+
+        checksum_after_with_ignore_list = dir_checksum(os.path.dirname(_file.name), ignore_list=[".aws-sam"])
+        self.assertEqual(checksum_before, checksum_after_with_ignore_list)
+
     def test_dir_cyclic_links(self):
         _file = tempfile.NamedTemporaryFile(delete=False, dir=self.temp_dir)
         _file.write(b"Testfile")