add basetag property

Signed-off-by: Tim van Katwijk <timvankatwijk@hotmail.com>

Author: tim-vk

dockerfile_parse/parser.py

@@ -401,7 +401,7 @@ def parent_images(self, parents):
             lines[instr['startline']:instr['endline']+1] = [instr['content']]
 
         self.lines = lines
-
+    
     @property
     def is_multistage(self):
         return len(self.parent_images) > 1
@@ -428,6 +428,21 @@ def baseimage(self, new_image):
             raise RuntimeError('No stage defined to set base image on')
         images[-1] = new_image
         self.parent_images = images
+    
+    @property
+    def basetag(self):
+        """
+        :return: tag of base image, i.e. tag of base image
+        """
+        _, tag = tag_from(self.baseimage)
+        return tag
+    
+    @basetag.setter
+    def basetag(self, new_tag):
+        """
+        only change the tag of the final stage FROM instruction
+        """
+        self.baseimage = tag_to(self.basetag, new_tag)
 
     @property
     def cmd(self):
@@ -917,7 +932,7 @@ def tag_to(image, new_tag):
 
     bare, _ = tag_from(image)
     return ":".join(filter(None, [bare.strip() if bare else None, new_tag.strip() if new_tag else None]))
-
+    
 def _endline(line):
     """
     Make sure the line ends with a single newline.

tests/test_parser.py

@@ -315,11 +315,22 @@ def test_get_baseimg_from_df(self, dfparser):
                           "LABEL a b\n"]
         assert dfparser.baseimage == 'fedora:latest'
 
+    def test_get_basetag_from_df(self,dfparser):
+        dfparser.lines = ["From fedora:latest\n",
+                          "LABEL a b\n"]
+        assert dfparser.basetag == 'latest'
+        
     def test_get_baseimg_from_arg(self, dfparser):
         dfparser.lines = ["ARG BASE=fedora:latest\n",
                           "FROM $BASE\n",
                           "LABEL a b\n"]
         assert dfparser.baseimage == 'fedora:latest'
+        
+    def test_get_basetag_from_arg(self, dfparser):
+        dfparser.lines = ["ARG BASE=fedora:latest\n",
+                          "FROM $BASE\n",
+                          "LABEL a b\n"]
+        assert dfparser.basetag == 'latest'
 
     def test_get_baseimg_from_build_arg(self, tmpdir):
         tmpdir_path = str(tmpdir.realpath())
@@ -331,6 +342,16 @@ def test_get_baseimg_from_build_arg(self, tmpdir):
         assert dfp.baseimage == 'fedora:latest'
         assert not dfp.args
 
+    def test_get_basetag_from_build_arg(self, tmpdir):
+        tmpdir_path = str(tmpdir.realpath())
+        b_args = {"BASE": "fedora:latest"}
+        dfp = DockerfileParser(tmpdir_path, env_replace=True, build_args=b_args)
+        dfp.lines = ["ARG BASE=centos:latest\n",
+                     "FROM $BASE\n",
+                     "LABEL a b\n"]
+        assert dfp.basetag == 'latest'
+        assert not dfp.args
+        
     def test_set_no_baseimage(self, dfparser):
         dfparser.lines = []
         with pytest.raises(RuntimeError):
@@ -556,6 +577,7 @@ def test_tag_to(self, from_image, from_tag, expect):
         result = tag_to(from_image, from_tag)
         assert result == expect
 
+        
     @pytest.mark.parametrize(('tag', 'expect'), [
         (
             "Tag",
@@ -617,8 +639,9 @@ def test_parent_images_missing_from(self, dfparser):
         assert dfparser.content.count('FROM') == 4
 
     def test_modify_instruction(self, dfparser):
-        FROM = ('ubuntu', 'fedora:❤')
+        FROM = ('ubuntu', 'fedora:theBest')
         CMD = ('old❤cmd', 'new❤command')
+        TAG = ('theBest', 'newtag')
         df_content = dedent("""\
             FROM {0}
             CMD {1}""").format(FROM[0], CMD[0])
@@ -628,6 +651,10 @@ def test_modify_instruction(self, dfparser):
         assert dfparser.baseimage == FROM[0]
         dfparser.baseimage = FROM[1]
         assert dfparser.baseimage == FROM[1]
+        
+        assert dfparser.basetag == TAG[0]
+        dfparser.basetag = TAG[1]
+        assert dfparser.basetag == TAG[1]
 
         assert dfparser.cmd == CMD[0]
         dfparser.cmd = CMD[1]