support --platform parameter in image_from

Signed-off-by: Tim van Katwijk <[email protected]>

Author: tim-vk

dockerfile_parse/parser.py

@@ -869,10 +869,12 @@ def image_from(from_value):
     :param from_value: string like "image:tag" or "image:tag AS name"
     :return: tuple of the image and stage name, e.g. ("image:tag", None)
     """
-    regex = re.compile(r"""(?xi)     # readable, case-insensitive regex
-        \s*                          # ignore leading whitespace
-        (?P<image> \S+ )             # image and optional tag
-        (?:                          # optional "AS name" clause for stage
+    regex = re.compile(r"""(?xi)        # readable, case-insensitive regex
+        \s*                             # ignore leading whitespace
+        (?P<platform> --platform=\S+)?  # optional platform parameter
+        \s*                             # more whitespaces
+        (?P<image> \S+ )                # image and optional tag
+        (?:                             # optional "AS name" clause for stage
             \s+ AS \s+
             (?P<name> \S+ )
         )?

tests/test_parser.py

@@ -312,6 +312,12 @@ def test_get_baseimg_from_df(self, dfparser):
         dfparser.lines = ["From fedora:latest\n",
                           "LABEL a b\n"]
         assert dfparser.baseimage == 'fedora:latest'
+        
+
+    def test_get_baseimg_from_df_with_platform(self, dfparser):
+        dfparser.lines = ["From --platform=linux/amd64 fedora:latest\n",
+                          "LABEL a b\n"]
+        assert dfparser.baseimage == 'fedora:latest'
 
     def test_get_baseimg_from_arg(self, dfparser):
         dfparser.lines = ["ARG BASE=fedora:latest\n",