Draft version of analyze multistage dockerfile

1. In tern\analyze\docker\dockerfile.py, add function
split_multistage_dockerfile_by_stage() to split by stage.

2. In tern\analyze\docker\run.py， add function
build_multistage(), this is a draft version for building and analyzing
multistage dockerfile.

Works towards tern-tools#612.

Signed-off-by: WangJL <hazard15020@gmail.com>

tern/analyze/docker/dockerfile.py

@@ -377,6 +377,38 @@ def get_multistage_image_dockerfiles(dfobj_multi):
     return file_path_list
 
 
+def split_multistage_dockerfile_by_stage(dfobj_multi):
+    file_path_list = []
+    structure = []
+    file_idx = 0
+    from_lines = check_multistage_dockerfile(dfobj_multi)
+    # Pop the first FROM
+    from_lines.pop(0)
+    for idx in range(len(dfobj_multi.structure)):
+        if idx in from_lines:
+            if structure:
+                file_path = dfobj_multi.filepath + '_stage_%d' % (file_idx)
+                # we make a new dir for the dockerfile of each stage.
+                if not os.path.isdir(file_path):
+                    os.mkdir(file_path)
+                file_path += '/Dockerfile'
+                file_idx += 1
+                write_dockerfile_by_structure(file_path, structure)
+                file_path_list.append(file_path)
+                structure.clear()
+        structure.append(dfobj_multi.structure[idx])
+    if structure:
+        file_path = dfobj_multi.filepath + '_stage_%d' % (file_idx)
+        # we make a new dir for the dockerfile of each stage.
+        if not os.path.isdir(file_path):
+            os.mkdir(file_path)
+        file_path += '/Dockerfile'
+        file_idx += 1
+        write_dockerfile_by_structure(file_path, structure)
+        file_path_list.append(file_path)
+    return file_path_list
+
+
 def write_dockerfile_by_structure(file_name, structure):
     """Given a dockerfile name and its structure, write the content into the
     dockerfile."""

tern/analyze/docker/run.py

@@ -181,3 +181,38 @@ def execute_dockerfile(args):  # noqa C901,R0912
     if args.name == 'report':
         if not args.keep_wd:
             report.clean_working_dir()
+
+
+def build_multistage(dockerfile_path, args):
+    """Given a multistage dockerfile, first get the dockerfiles for each
+    stage and then build the dockerfiles.
+    TO DO:
+    1. Add image analyze
+    2. Clean the temp dockerfiles"""
+    dfobj_multi = dockerfile.get_dockerfile_obj(dockerfile_path)
+    file_path_list = dockerfile.get_multistage_image_dockerfiles(dfobj_multi)
+    stage_list = dockerfile.split_multistage_dockerfile_by_stage(dfobj_multi)
+    print(file_path_list)
+    print(stage_list)
+    for idx, dfile in enumerate(file_path_list):
+        args.output_file = '/home/vagrant/output_%d.html' % (idx)
+        dfobj = dockerfile.get_dockerfile_obj(dfile)
+        stageobj = dockerfile.get_dockerfile_obj(stage_list[idx])
+        # expand potential ARG values so base image tag is correct
+        dockerfile.expand_arg(dfobj)
+        dockerfile.expand_vars(dfobj)
+        report.setup(dfobj=dfobj)
+        # attempt to build the image
+        logger.debug('Building Docker image...')
+        # placeholder to check if we can analyze the full image
+        build, _ = dhelper.is_build()
+        print(build)
+        # TO DO: Add image analyze here to analyze each image.
+        if build:
+            # attempt to get built image metadata
+            image_tag_string = dhelper.get_dockerfile_image_tag()
+            print(image_tag_string)
+            full_image = report.load_full_image(image_tag_string)
+            analyze(full_image, args, False, stageobj)
+            container.remove_image(full_image.repotag)
+            report.report_out(args, full_image)