refactor(pypi): move absolute_url to whl_library

With this PR we move the processing of the `index_url` to the
`whl_library` as a preparatory step for easier `facts` implementation.
The motivation is many-fold:
1. Do not have too much duplication in the facts file by potentially
   naturally eliminating the `index_url` prefix from the `whls` if it
   appears like so on the index contents.
2. Avoid doing `envsubst` too early and have logic that has to deal with
   it.
3. Make the cache just return fact values from the lock file in the
   future instead of needing to change to an absolute URL and do
   envsubst on it.
4. We should have a better performance because we should be doing way
   fewer calls to make the URL absolute during parsing of the index.
5. With the `index_url` passed to the `whl_library`, we can help out the
   `purl` construction as what has been discussed in bazel-contrib#3531 about wheels
   from non-public indexes.

Summary:
- Attempt to put the `index_url` in the fewest structs possible.
- Extract the `urllib` utilities file for manipulation of the URLs.
- Simplify tests testing the `absolute_url` logic.

Work towards bazel-contrib#2731

Author: aignas

python/private/pypi/BUILD.bazel

@@ -418,13 +418,19 @@ bzl_library(
     srcs = ["simpleapi_download.bzl"],
     deps = [
         ":parse_simpleapi_html_bzl",
+        ":urllib_bzl",
         "//python/private:auth_bzl",
         "//python/private:normalize_name_bzl",
         "//python/private:text_util_bzl",
         "@bazel_features//:features",
     ],
 )
 
+bzl_library(
+    name = "urllib_bzl",
+    srcs = ["urllib.bzl"],
+)
+
 bzl_library(
     name = "version_from_filename_bzl",
     srcs = ["version_from_filename.bzl"],
@@ -474,6 +480,7 @@ bzl_library(
         ":patch_whl_bzl",
         ":pep508_requirement_bzl",
         ":pypi_repo_utils_bzl",
+        ":urllib_bzl",
         ":whl_extract_bzl",
         ":whl_metadata_bzl",
         ":whl_target_platforms_bzl",

python/private/pypi/hub_builder.bzl

@@ -599,6 +599,7 @@ def _create_whl_repos(
         for src in whl.srcs:
             repo = _whl_repo(
                 src = src,
+                index_url = whl.index_url,
                 whl_library_args = whl_library_args,
                 download_only = pip_attr.download_only,
                 netrc = self._config.netrc or pip_attr.netrc,
@@ -678,6 +679,7 @@ def _whl_repo(
         *,
         src,
         whl_library_args,
+        index_url,
         is_multiple_versions,
         download_only,
         netrc,
@@ -731,6 +733,8 @@ def _whl_repo(
         args["netrc"] = netrc
     if auth_patterns:
         args["auth_patterns"] = auth_patterns
+    if index_url:
+        args["index_url"] = index_url
 
     args["urls"] = [src.url]
     args["sha256"] = src.sha256

python/private/pypi/parse_requirements.bzl

@@ -188,10 +188,11 @@ def parse_requirements(
             for p in r.target_platforms:
                 requirement_target_platforms[p] = None
 
+        pkg_sources = index_urls.get(name)
         package_srcs = _package_srcs(
             name = name,
             reqs = reqs,
-            index_urls = index_urls,
+            pkg_sources = pkg_sources,
             platforms = platforms,
             extract_url_srcs = extract_url_srcs,
             logger = logger,
@@ -216,6 +217,7 @@ def parse_requirements(
             name = normalize_name(name),
             is_exposed = len(requirement_target_platforms) == len(requirements),
             is_multiple_versions = len(reqs.values()) > 1,
+            index_url = pkg_sources.index_url if pkg_sources else "",
             srcs = package_srcs,
         )
         ret.append(item)
@@ -234,7 +236,7 @@ def _package_srcs(
         *,
         name,
         reqs,
-        index_urls,
+        pkg_sources,
         platforms,
         logger,
         extract_url_srcs):
@@ -253,7 +255,7 @@ def _package_srcs(
             dist, can_fallback = _add_dists(
                 requirement = r,
                 target_platform = platforms.get(target_platform),
-                index_urls = index_urls.get(name),
+                index_urls = pkg_sources,
                 logger = logger,
             )
             logger.debug(lambda: "The whl dist is: {}".format(dist.filename if dist else dist))

python/private/pypi/parse_simpleapi_html.bzl

@@ -18,11 +18,10 @@ Parse SimpleAPI HTML in Starlark.
 
 load(":version_from_filename.bzl", "version_from_filename")
 
-def parse_simpleapi_html(*, url, content):
+def parse_simpleapi_html(*, content):
     """Get the package URLs for given shas by parsing the Simple API HTML.
 
     Args:
-        url(str): The URL that the HTML content can be downloaded from.
         content(str): The Simple API HTML content.
 
     Returns:
@@ -57,7 +56,6 @@ def parse_simpleapi_html(*, url, content):
     sha256s_by_version = {}
     for line in lines[1:]:
         dist_url, _, tail = line.partition("#sha256=")
-        dist_url = _absolute_url(url, dist_url)
 
         sha256, _, tail = tail.partition("\"")
 
@@ -87,7 +85,7 @@ def parse_simpleapi_html(*, url, content):
                 url = dist_url,
                 sha256 = sha256,
                 metadata_sha256 = metadata_sha256,
-                metadata_url = _absolute_url(url, metadata_url) if metadata_url else "",
+                metadata_url = metadata_url,
                 yanked = yanked,
             )
         else:
@@ -106,47 +104,3 @@ def parse_simpleapi_html(*, url, content):
         whls = whls,
         sha256s_by_version = sha256s_by_version,
     )
-
-def _get_root_directory(url):
-    scheme_end = url.find("://")
-    if scheme_end == -1:
-        fail("Invalid URL format")
-
-    scheme = url[:scheme_end]
-    host_end = url.find("/", scheme_end + 3)
-    if host_end == -1:
-        host_end = len(url)
-    host = url[scheme_end + 3:host_end]
-
-    return "{}://{}".format(scheme, host)
-
-def _is_downloadable(url):
-    """Checks if the URL would be accepted by the Bazel downloader.
-
-    This is based on Bazel's HttpUtils::isUrlSupportedByDownloader
-    """
-    return url.startswith("http://") or url.startswith("https://") or url.startswith("file://")
-
-def _absolute_url(index_url, candidate):
-    if candidate == "":
-        return candidate
-
-    if _is_downloadable(candidate):
-        return candidate
-
-    if candidate.startswith("/"):
-        # absolute path
-        root_directory = _get_root_directory(index_url)
-        return "{}{}".format(root_directory, candidate)
-
-    if candidate.startswith(".."):
-        # relative path with up references
-        candidate_parts = candidate.split("..")
-        last = candidate_parts[-1]
-        for _ in range(len(candidate_parts) - 1):
-            index_url, _, _ = index_url.rstrip("/").rpartition("/")
-
-        return "{}/{}".format(index_url, last.strip("/"))
-
-    # relative path without up-references
-    return "{}/{}".format(index_url.rstrip("/"), candidate)

python/private/pypi/pypi_cache.bzl

@@ -9,7 +9,11 @@ In the future the same will be used to:
 """
 
 def pypi_cache(store = None):
-    """The cache for PyPI index queries."""
+    """The cache for PyPI index queries.
+
+    Currently the key is of the following structure:
+    (url, real_url)
+    """
 
     # buildifier: disable=uninitialized
     self = struct(
@@ -29,6 +33,10 @@ def _pypi_cache_setdefault(self, key, parsed_result):
         key: {type}`str` The cache key, can be any string.
         parsed_result: {type}`struct` The result of `parse_simpleapi_html` function.
 
+    index_url and distribution is used to write to the MODULE.bazel.lock file as facts
+    real_index_url and distribution is used to write to in-memory cache to ensure that there are
+    no duplicate calls to the PyPI indexes
+
     Returns:
         The `parse_result`.
     """

python/private/pypi/simpleapi_download.bzl

@@ -22,6 +22,7 @@ load("//python/private:envsubst.bzl", "envsubst")
 load("//python/private:normalize_name.bzl", "normalize_name")
 load("//python/private:text_util.bzl", "render")
 load(":parse_simpleapi_html.bzl", "parse_simpleapi_html")
+load(":urllib.bzl", "urllib")
 
 def simpleapi_download(
         ctx,
@@ -92,13 +93,14 @@ def simpleapi_download(
         sources = [pkg for pkg in attr.sources if pkg not in found_on_index]
         for pkg in sources:
             pkg_normalized = normalize_name(pkg)
+            url = urllib.strip_empty_path_segments("{index_url}/{distribution}/".format(
+                index_url = index_url_overrides.get(pkg_normalized, index_url).rstrip("/"),
+                distribution = pkg,
+            ))
             result = read_simpleapi(
                 ctx = ctx,
-                url = "{}/{}/".format(
-                    index_url_overrides.get(pkg_normalized, index_url).rstrip("/"),
-                    pkg,
-                ),
                 attr = attr,
+                url = url,
                 cache = cache,
                 get_auth = get_auth,
                 **download_kwargs
@@ -108,9 +110,10 @@ def simpleapi_download(
                 async_downloads[pkg] = struct(
                     pkg_normalized = pkg_normalized,
                     wait = result.wait,
+                    url = url,
                 )
             elif result.success:
-                contents[pkg_normalized] = result.output
+                contents[pkg_normalized] = _with_index_url(url, result.output)
                 found_on_index[pkg] = index_url
 
         if not async_downloads:
@@ -122,7 +125,7 @@ def simpleapi_download(
             result = download.wait()
 
             if result.success:
-                contents[download.pkg_normalized] = result.output
+                contents[download.pkg_normalized] = _with_index_url(download.url, result.output)
                 found_on_index[pkg] = index_url
 
     failed_sources = [pkg for pkg in attr.sources if pkg not in found_on_index]
@@ -168,14 +171,14 @@ def _read_simpleapi(ctx, url, attr, cache, get_auth = None, **download_kwargs):
 
     Args:
         ctx: The module_ctx or repository_ctx.
-        url: str, the url parameter that can be passed to ctx.download.
+        url: {type}`str`, the url parameter that can be passed to ctx.download.
         attr: The attribute that contains necessary info for downloading. The
           following attributes must be present:
-           * envsubst: The envsubst values for performing substitutions in the URL.
-           * netrc: The netrc parameter for ctx.download, see http_file for docs.
+           * envsubst: {type}`dict[str, str]` for performing substitutions in the URL.
+           * netrc: The netrc parameter for ctx.download, see {obj}`http_file` for docs.
            * auth_patterns: The auth_patterns parameter for ctx.download, see
-               http_file for docs.
-        cache: A dict for storing the results.
+               {obj}`http_file` for docs.
+        cache: {type}`struct` the `pypi_cache` instance.
         get_auth: A function to get auth information. Used in tests.
         **download_kwargs: Any extra params to ctx.download.
             Note that output and auth will be passed for you.
@@ -189,9 +192,9 @@ def _read_simpleapi(ctx, url, attr, cache, get_auth = None, **download_kwargs):
     # them to ctx.download if we want to correctly handle the relative URLs.
     # TODO: Add a test that env subbed index urls do not leak into the lock file.
 
-    real_url = strip_empty_path_segments(envsubst(url, attr.envsubst, ctx.getenv))
+    real_url = urllib.strip_empty_path_segments(envsubst(url, attr.envsubst, ctx.getenv))
 
-    cache_key = real_url
+    cache_key = (url, real_url)
     cached_result = cache.get(cache_key)
     if cached_result:
         return struct(success = True, output = cached_result)
@@ -225,41 +228,43 @@ def _read_simpleapi(ctx, url, attr, cache, get_auth = None, **download_kwargs):
     if download_kwargs.get("block") == False:
         # Simulate the same API as ctx.download has
         return struct(
-            wait = lambda: _read_index_result(ctx, download.wait(), output, real_url, cache, cache_key),
+            wait = lambda: _read_index_result(
+                ctx,
+                result = download.wait(),
+                output = output,
+                cache = cache,
+                cache_key = cache_key,
+            ),
         )
 
-    return _read_index_result(ctx, download, output, real_url, cache, cache_key)
-
-def strip_empty_path_segments(url):
-    """Removes empty path segments from a URL. Does nothing for urls with no scheme.
-
-    Public only for testing.
-
-    Args:
-        url: The url to remove empty path segments from
-
-    Returns:
-        The url with empty path segments removed and any trailing slash preserved.
-        If the url had no scheme it is returned unchanged.
-    """
-    scheme, _, rest = url.partition("://")
-    if rest == "":
-        return url
-    stripped = "/".join([p for p in rest.split("/") if p])
-    if url.endswith("/"):
-        return "{}://{}/".format(scheme, stripped)
-    else:
-        return "{}://{}".format(scheme, stripped)
+    return _read_index_result(
+        ctx,
+        result = download,
+        output = output,
+        cache = cache,
+        cache_key = cache_key,
+    )
 
-def _read_index_result(ctx, result, output, url, cache, cache_key):
+def _read_index_result(ctx, *, result, output, cache, cache_key):
     if not result.success:
         return struct(success = False)
 
     content = ctx.read(output)
 
-    output = parse_simpleapi_html(url = url, content = content)
+    output = parse_simpleapi_html(content = content)
     if output:
         cache.setdefault(cache_key, output)
-        return struct(success = True, output = output, cache_key = cache_key)
+        return struct(success = True, output = output)
     else:
         return struct(success = False)
+
+def _with_index_url(index_url, values):
+    if not values:
+        return values
+
+    return struct(
+        sdists = values.sdists,
+        whls = values.whls,
+        sha256s_by_version = values.sha256s_by_version,
+        index_url = index_url,
+    )