Add documentation for --prefer-source option

Signed-off-by: Tushar Goel <tushar.goel.dav@gmail.com>

Author: TG1999

CHANGELOG.rst

@@ -5,7 +5,8 @@ Changelog
 v0.9.1
 ------
 
-- Add --prefer-source option.
+- Add --prefer-source option, to prefer source packages over binary ones
+  if no source distribution is available then binary distributions are used.
 
 
 v0.9.0

docs/source/dependencies-design.rst

@@ -223,6 +223,9 @@ repositories.
    PyPI "simple" API. Both the "simple" API and the PyPI JSON
    "warehouse-style" API are supported.
 
+- ``--prefer-source``: when set, prefer source distribution instead 
+  of binary distribution. In case there is no source distribution
+  available, the tool should provide binary distribution. 
 
 Strategy and error processing:
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

src/python_inspector/package_data.py

@@ -33,6 +33,8 @@ def get_pypi_data_from_purl(
     ``purl`` is a package-url of pypi type
     ``environment`` is a `Environment` object defaulting Python version 3.8 and linux OS
     ``repos`` is a list of `PypiSimpleRepository` objects
+    ``prefer_source`` is a boolean value to prefer source distribution over wheel,
+    if no source distribution is available then wheel is used
     """
     purl = PackageURL.from_string(purl)
     name = purl.name
@@ -53,7 +55,18 @@ def get_pypi_data_from_purl(
     bug_tracking_url = get_pypi_bugtracker_url(project_urls)
     python_version = get_python_version_from_env_tag(python_version=environment.python_version)
     valid_distribution_urls = []
-    if not prefer_source:
+
+    valid_distribution_urls.append(
+        get_sdist_download_url(
+            purl=purl,
+            repos=repos,
+            python_version=python_version,
+        )
+    )
+
+    # if prefer_source is True then only source distribution is used
+    # in case of no source distribution available then wheel is used
+    if not valid_distribution_urls or not prefer_source:
         valid_distribution_urls.extend(
             list(
                 get_wheel_download_urls(
@@ -64,13 +77,7 @@ def get_pypi_data_from_purl(
                 )
             )
         )
-    valid_distribution_urls.append(
-        get_sdist_download_url(
-            purl=purl,
-            repos=repos,
-            python_version=python_version,
-        )
-    )
+
     urls = response.get("urls") or []
     for url in urls:
         dist_url = url.get("url")

src/python_inspector/resolve_cli.py

@@ -154,7 +154,8 @@ def print_version(ctx, param, value):
 @click.option(
     "--prefer-source",
     is_flag=True,
-    help="Prefer source distributions over binary distributions.",
+    help="Prefer source distributions over binary distributions"
+    " if no source distribution is available then binary distributions are used",
 )
 @click.option(
     "--verbose",
@@ -203,6 +204,7 @@ def resolve_dependencies(
     to PyPI.org.
 
     Provide source distributions over binary distributions with the --prefer-source
+    option. If no source distribution is available then binary distributions are used.
 
     Error and progress are printed to stderr.
 

src/python_inspector/utils_pypi.py

@@ -336,7 +336,7 @@ def download_sdist(
     fetched_sdist_filename = None
 
     for repo in repos:
-        sdist = get_valid_sdist(repo, name, version, python_version=DEFAULT_PYTHON_VERSION)
+        sdist = get_valid_sdist(repo, name, version, python_version=python_version)
         if not sdist:
             if TRACE_DEEP:
                 print(f"    download_sdist: No valid sdist for {name}=={version}")