Improve package datafile handlers

* Add new attributes to the DatafileHandler class for a datasource type
  and the supported operating systems
* Add and test new validate() method to validate DatafileHandler
  collection correctness
* Apply minor refactorings and code formatting

Signed-off-by: Philippe Ombredanne <pombredanne@nexb.com>

Author: pombredanne

src/packagedcode/__init__.py

@@ -7,8 +7,6 @@
 # See https://aboutcode.org for more information about nexB OSS projects.
 #
 
-import attr
-
 from commoncode.system import on_linux
 from packagedcode import about
 from packagedcode import alpine
@@ -254,6 +252,7 @@
     ]
 )
 
+# registry of all handler classes keyed by datasource_id
 HANDLER_BY_DATASOURCE_ID = {handler.datasource_id: handler for handler in ALL_DATAFILE_HANDLERS}
 
 
@@ -263,8 +262,8 @@ class UnknownPackageDatasource(Exception):
 
 def get_package_handler(package_data):
     """
-    Return the DatafileHandler class that corresponds to a ``package_data``
-    PackageData object. Raise a UnknownPackageDatasource error if the
+    Return the DatafileHandler class that for a ``package_data``
+    PackageData class datasource_id. Raise a UnknownPackageDatasource error if the
     DatafileHandler is not found.
     """
     ppc = HANDLER_BY_DATASOURCE_ID.get(package_data.datasource_id)

src/packagedcode/alpine.py

@@ -58,6 +58,7 @@ def get_license_detections_and_expression(package):
 
 class AlpineInstalledDatabaseHandler(models.DatafileHandler):
     datasource_id = 'alpine_installed_db'
+    datasource_type = 'sys'
     path_patterns = ('*lib/apk/db/installed',)
     default_package_type = 'alpine'
     description = 'Alpine Linux installed package database'

src/packagedcode/debian.py

@@ -223,6 +223,7 @@ def assign_package_to_resources(cls, package, resource, codebase, package_adder)
 
 class DebianInstalledStatusDatabaseHandler(models.DatafileHandler):
     datasource_id = 'debian_installed_status_db'
+    datasource_type = 'sys'
     default_package_type = 'deb'
     path_patterns = ('*var/lib/dpkg/status',)
     description = 'Debian installed packages database'
@@ -391,6 +392,7 @@ def assemble(cls, package_data, resource, codebase, package_adder):
 
 class DebianDistrolessInstalledDatabaseHandler(models.DatafileHandler):
     datasource_id = 'debian_distroless_installed_db'
+    datasource_type = 'sys'
     default_package_type = 'deb'
     path_patterns = ('*var/lib/dpkg/status.d/*',)
     description = 'Debian distroless installed database'
@@ -474,6 +476,7 @@ class DebianInstalledFilelistHandler(models.DatafileHandler):
     # seen in installed rootfs in:
     #  - /var/lib/dpkg/info/<package name>.list
     datasource_id = 'debian_installed_files_list'
+    datasource_type = 'sys'
     default_package_type = 'deb'
     path_patterns = (
         '*var/lib/dpkg/info/*.list',
@@ -499,6 +502,7 @@ class DebianInstalledMd5sumFilelistHandler(models.DatafileHandler):
     #  - /var/lib/dpkg/info/<package name>.md5sums
     #  - /var/lib/dpkg/info/<package name:arch>.md5sums
     datasource_id = 'debian_installed_md5sums'
+    datasource_type = 'sys'
     default_package_type = 'deb'
     path_patterns = (
         '*var/lib/dpkg/info/*.md5sums',

src/packagedcode/maven.py

@@ -55,6 +55,7 @@
 there is no pom.properties check if there are side-by-side artifacts
 """
 
+
 class MavenBasePackageHandler(models.DatafileHandler):
 
     @classmethod
@@ -71,7 +72,7 @@ def assemble(cls, package_data, resource, codebase, package_adder=models.add_to_
         datafile_path = resource.path
 
         # This order is important as we want pom.xml to be used for package
-        # creation and then to update from MANIFEST later 
+        # creation and then to update from MANIFEST later
         manifest_path_pattern = '*/META-INF/MANIFEST.MF'
         nested_pom_xml_path_pattern = '*/META-INF/maven/**/pom.xml'
         datafile_name_patterns = (nested_pom_xml_path_pattern, manifest_path_pattern)
@@ -103,7 +104,7 @@ def assemble(cls, package_data, resource, codebase, package_adder=models.add_to_
             return
 
         if manifests and pom_xmls:
-            #raise Exception(resource.path, meta_inf_resource, datafile_name_patterns, package_adder)
+            # raise Exception(resource.path, meta_inf_resource, datafile_name_patterns, package_adder)
             parent_resource = meta_inf_resource.parent(codebase)
             if not parent_resource:
                 parent_resource = meta_inf_resource
@@ -272,7 +273,7 @@ def assign_package_to_resources(cls, package, resource, codebase, package_adder)
             for child in root.walk(codebase):
                 if 'pom.xml' in child.path:
                     number_poms += 1
-            
+
             if number_poms > 1:
                 root = resource
             else:
@@ -315,7 +316,7 @@ def parse(cls, location, package_only=False):
             if TRACE:
                 logger.debug(f'MavenPomPropertiesHandler.parse: properties: {properties!r}')
             if properties:
-                yield from cls.parse_pom_properties(properties=properties, package_only=package_only) 
+                yield from cls.parse_pom_properties(properties=properties, package_only=package_only)
 
     @classmethod
     def parse_pom_properties(cls, properties, package_only=False):
@@ -1308,11 +1309,14 @@ def _parse(
     )
     return MavenPackageData.from_data(package_data, package_only)
 
+
 class MavenPackageData(models.PackageData):
 
     datasource_id = 'maven_pom'
 
+    @classmethod
     def get_license_detections_for_extracted_license_statement(
+        cls,
         extracted_license,
         try_as_expression=True,
         approximate=True,
@@ -1321,16 +1325,16 @@ def get_license_detections_for_extracted_license_statement(
         from packagedcode.licensing import get_normalized_license_detections
         from packagedcode.licensing import get_license_detections_for_extracted_license_statement
 
-        if not MavenPackageData.check_extracted_license_statement_structure(extracted_license):
+        if not cls.check_extracted_license_statement_structure(extracted_license):
             return get_normalized_license_detections(
                 extracted_license=extracted_license,
                 try_as_expression=try_as_expression,
                 approximate=approximate,
                 expression_symbols=expression_symbols,
             )
-        
+
         new_extracted_license = extracted_license.copy()
-        
+
         for license_entry in new_extracted_license:
             license_entry.pop("distribution")
             if not license_entry.get("name"):
@@ -1349,8 +1353,8 @@ def get_license_detections_for_extracted_license_statement(
             expression_symbols=expression_symbols,
         )
 
-
-    def check_extracted_license_statement_structure(extracted_license):
+    @classmethod
+    def check_extracted_license_statement_structure(cls, extracted_license):
 
         is_list_of_mappings = False
         if not isinstance(extracted_license, list):
@@ -1362,7 +1366,7 @@ def check_extracted_license_statement_structure(extracted_license):
             if not isinstance(extracted_license_item, dict):
                 is_list_of_mappings = False
                 break
-        
+
         return is_list_of_mappings
 
 

src/packagedcode/models.py

@@ -7,29 +7,30 @@
 # See https://aboutcode.org for more information about nexB OSS projects.
 #
 
+import logging
 import os
 import uuid
-from fnmatch import fnmatchcase
-import logging
 import sys
 
+from fnmatch import fnmatchcase
+
 import attr
-from packageurl import normalize_qualifiers
-from packageurl import PackageURL
 import saneyaml
 
 from commoncode import filetype
+from commoncode.fileutils import as_posixpath
 from commoncode.datautils import choices
 from commoncode.datautils import Boolean
 from commoncode.datautils import Date
 from commoncode.datautils import Integer
 from commoncode.datautils import List
 from commoncode.datautils import Mapping
 from commoncode.datautils import String
-from commoncode.fileutils import as_posixpath
 from commoncode.resource import Resource
 from license_expression import combine_expressions
 from license_expression import Licensing
+from packageurl import normalize_qualifiers
+from packageurl import PackageURL
 
 try:
     from typecode import contenttype
@@ -41,6 +42,7 @@
 except ImportError:
     licensing = None
 
+# FIXME: what if licensing is not importable?
 from packagedcode.licensing import get_declared_license_expression_spdx
 
 """
@@ -963,7 +965,7 @@ def get_license_detections_and_expression(self):
             return [], None
 
         if self.datasource_id:
-            default_relation_license=get_default_relation_license(
+            default_relation_license = get_default_relation_license(
                 datasource_id=self.datasource_id,
             )
         else:
@@ -1017,12 +1019,11 @@ def add_to_package(package_uid, resource, codebase):
 
 class DatafileHandler:
     """
-    A base handler class to handle any package manifests, lockfiles and data
-    files. Each subclass handles a package datafile format to parse datafiles
-    and assemble Package and Depdencies from these:
+    A base handler class to handle any package manifest, lockfile, package database
+    and related data files. Each subclass handles a package datafile format to parse
+    datafiles and assemble Package and Dependencies from these:
 
     - parses a datafile format and yields package data.
-
     - assembles this datafile package data in top-level packages and dependencies
     - assigns package files to their package
     """
@@ -1033,6 +1034,16 @@ class DatafileHandler:
     # can only contain ASCII letters, digits and underscore. Must be lowercase
     datasource_id = None
 
+    # style of package data processed by this handler, either app for application package like npm,
+    # sys for system packages like rpm, or info for informational data file that provides hints but
+    # is not a package manifest, like with a README file
+    # possible values are app, sys and info
+    datasource_type = 'app'
+
+    # tuple of specifically supported operating systems. If None or empty, all platforms are supported
+    # possible values are win, mac, linux, freebsd
+    supported_oses = tuple()
+
     # Sequence of known fnmatch-style case-insensitive glob patterns (e.g., Unix
     # shell style patterns) that apply on the whole POSIX path for package
     # datafiles recognized and parsed by this parser. See fnmatch.fnmatch().
@@ -1053,7 +1064,7 @@ class DatafileHandler:
     # Informational: Default primary language for this parser.
     default_primary_language = None
 
-    # If the datafilehandler contains only resolved dependencies
+    # If the handler is for a lockfile that contains locked/pinned, pre-resolved dependencies
     is_lockfile = False
 
     # Informational: Description of this parser
@@ -1062,7 +1073,9 @@ class DatafileHandler:
     # Informational: URL that documents this file format
     documentation_url = None
 
-    # Default Relation between license elements detected in an `extracted_license_statement`
+    # Default license expression relation between the license detected in an
+    # `extracted_license_statement` for this data file.
+    # This may vary for each data file based on conventions and specifications.
     default_relation_license = None
 
     @classmethod
@@ -1491,11 +1504,44 @@ def get_top_level_resources(cls, manifest_resource, codebase):
         """
         pass
 
+    @classmethod
+    def validate(cls):
+        """
+        Validate this class.
+        Raise ImproperlyConfiguredDatafileHandler exception on errors.
+        """
+
+        did = cls.datasource_id
+        if not did:
+            raise ImproperlyConfiguredDatafileHandler(
+                f'The handler {cls!r} has an empty datasource_id {did!r}.')
+
+        DATASOURCE_TYPES = 'app', 'sys', 'info',
+        dfs = cls.datasource_type
+        if dfs not in DATASOURCE_TYPES:
+            raise ImproperlyConfiguredDatafileHandler(
+                f'The handler {did!r} : {cls!r} has an invalid '
+                f'datasource_type: {dfs!r}: must be one of {DATASOURCE_TYPES!r}.'
+            )
+
+        oses = 'linux', 'win', 'max', 'freebsd',
+        soses = cls.supported_oses
+        if soses and not all(s in oses for s in soses):
+            raise ImproperlyConfiguredDatafileHandler(
+                f'The handler {cls.datasource_id!r} : {cls!r} has invalid '
+                f'supported_oses: {soses!r}: must be empty or among {oses!r}'
+            )
+
+
+class ImproperlyConfiguredDatafileHandler(Exception):
+    """ScanCode Package Datafile Handler is not properly configured"""
+    pass
+
 
 class NonAssemblableDatafileHandler(DatafileHandler):
     """
-    A handler that has no default implmentation for the assemble method, e.g.,
-    it will not alone trigger the creation of a top-level Pacakge.
+    A handler with a default implementation of an assemble method doing nothing, e.g.,
+    it will not alone trigger the creation of a top-level Package.
     """
 
     @classmethod
@@ -1528,8 +1574,8 @@ def build_purl(mapping):
     subpath = mapping.get('subpath')
     return PackageURL(
         type=ptype,
-        name=name,
         namespace=namespace,
+        name=name,
         version=version,
         qualifiers=qualifiers,
         subpath=subpath,
@@ -1601,10 +1647,10 @@ def from_package_data(cls, package_data, datafile_path, package_only=False):
                     license_match['from_file'] = datafile_path
 
         package = cls.from_dict(package_data_mapping)
-        
+
         if not package.package_uid:
             package.package_uid = build_package_uid(package.purl)
-        
+
         if not package_only:
             package.populate_license_fields()
             package.populate_holder_field()
@@ -1763,7 +1809,7 @@ def refresh_license_expressions(self, default_relation='AND'):
             self.declared_license_expression_spdx = get_declared_license_expression_spdx(
                 declared_license_expression=self.declared_license_expression,
             )
-        
+
         if self.other_license_detections:
             self.other_license_expression = str(combine_expressions(
                 expressions=[

src/packagedcode/msi.py

@@ -195,6 +195,7 @@ class MsiInstallerHandler(models.DatafileHandler):
     default_package_type = 'msi'
     description = 'Microsoft MSI installer'
     documentation_url = 'https://docs.microsoft.com/en-us/windows/win32/msi/windows-installer-portal'
+    supported_oses = ('linux',)
 
     @classmethod
     def parse(cls, location, package_only=False):

src/packagedcode/pypi.py

@@ -1093,7 +1093,7 @@ def parse(cls, location, package_only=False):
                         package_only=package_only,
                     )
 
-
+# FIXME: this is NOT used
 class PypiSdistArchiveHandler(models.DatafileHandler):
     datasource_id = 'pypi_sdist'
     path_patterns = ('*.tar.gz', '*.tar.bz2', '*.zip',)