Get rid of the LockfileContent class (pantsbuild#18305)

This is a step towards greater unification of user and tool lockfiles.

LockfileContent existed primarily to carry the default lockfile content
for tools, as read from a resource. This led to a lot of 
`Lockfile | LockfileContent` type signatures and
subsequent type-testing on the receiving end. 

Instead, the Lockfile class now takes an URL instead of a path (with
path-like URLs still supported), and we introduce a 
`resource://package/path` URL to represent lockfiles embedded in 
the Pants binary as a resource.

src/python/pants/backend/python/goals/export.py

@@ -266,8 +266,8 @@ async def export_virtualenv_for_resolve(
     if lockfile_path:
         # It's a user resolve.
         lockfile = Lockfile(
-            file_path=lockfile_path,
-            file_path_description_of_origin=f"the resolve `{resolve}`",
+            url=lockfile_path,
+            url_description_of_origin=f"the resolve `{resolve}`",
             resolve_name=resolve,
         )
 

src/python/pants/backend/python/subsystems/python_tool_base.py

@@ -3,7 +3,6 @@
 
 from __future__ import annotations
 
-import importlib.resources
 from typing import ClassVar, Iterable, Sequence
 
 from pants.backend.python.target_types import ConsoleScript, EntryPoint, MainSpecification
@@ -14,12 +13,11 @@
     LoadedLockfile,
     LoadedLockfileRequest,
     Lockfile,
-    LockfileContent,
     PexRequirements,
 )
 from pants.core.goals.generate_lockfiles import DEFAULT_TOOL_LOCKFILE, NO_TOOL_LOCKFILE
 from pants.core.util_rules.lockfile_metadata import calculate_invalidation_digest
-from pants.engine.fs import Digest, FileContent
+from pants.engine.fs import Digest
 from pants.engine.internals.selectors import Get
 from pants.engine.rules import rule_helper
 from pants.option.errors import OptionsError
@@ -152,24 +150,21 @@ def pex_requirements(
 
         hex_digest = calculate_invalidation_digest(requirements)
 
-        lockfile: LockfileContent | Lockfile
         if self.lockfile == DEFAULT_TOOL_LOCKFILE:
             assert self.default_lockfile_resource is not None
-            lockfile = LockfileContent(
-                file_content=FileContent(
-                    f"{self.options_scope}_default.lock",
-                    importlib.resources.read_binary(*self.default_lockfile_resource),
-                ),
-                lockfile_hex_digest=hex_digest,
-                resolve_name=self.options_scope,
-            )
+            pkg, path = self.default_lockfile_resource
+            url = f"resource://{pkg}/{path}"
+            origin = f"The built-in default lockfile for {self.options_scope}"
         else:
-            lockfile = Lockfile(
-                file_path=self.lockfile,
-                file_path_description_of_origin=f"the option `[{self.options_scope}].lockfile`",
-                lockfile_hex_digest=hex_digest,
-                resolve_name=self.options_scope,
-            )
+            url = self.lockfile
+            origin = f"the option `[{self.options_scope}].lockfile`"
+
+        lockfile = Lockfile(
+            url=url,
+            url_description_of_origin=origin,
+            lockfile_hex_digest=hex_digest,
+            resolve_name=self.options_scope,
+        )
         return EntireLockfile(lockfile, complete_req_strings=tuple(requirements))
 
     @property

src/python/pants/backend/python/typecheck/mypy/subsystem.py

@@ -221,8 +221,8 @@ def extra_type_stubs_pex_request(
             requirements = PexRequirements(self.extra_type_stubs)
         else:
             tool_lockfile = Lockfile(
-                file_path=self.extra_type_stubs_lockfile,
-                file_path_description_of_origin=(
+                url=self.extra_type_stubs_lockfile,
+                url_description_of_origin=(
                     f"the option `[{self.options_scope}].extra_type_stubs_lockfile`"
                 ),
                 lockfile_hex_digest=calculate_invalidation_digest(self.extra_type_stubs),

src/python/pants/backend/python/util_rules/lockfile_diff.py

@@ -20,7 +20,7 @@
     LoadedLockfile,
     LoadedLockfileRequest,
     Lockfile,
-    LockfileContent,
+    strip_comments_from_pex_json_lockfile,
 )
 from pants.base.exceptions import EngineError
 from pants.core.goals.generate_lockfiles import LockfileDiff, LockfilePackages, PackageName
@@ -72,42 +72,43 @@ def _pex_lockfile_requirements(
 
 
 @rule_helper
-async def _parse_lockfile(lockfile: Lockfile | LockfileContent) -> FrozenDict[str, Any] | None:
+async def _parse_lockfile(lockfile: Lockfile) -> FrozenDict[str, Any] | None:
     try:
         loaded = await Get(
             LoadedLockfile,
             LoadedLockfileRequest(lockfile),
         )
         fc = await Get(DigestContents, Digest, loaded.lockfile_digest)
-        parsed_lockfile = json.loads(fc[0].content)
-        return FrozenDict.deep_freeze(parsed_lockfile)
+        parsed = await _parse_lockfile_content(next(iter(fc)).content, lockfile.url)
+        return parsed
     except EngineError:
         # May fail in case the file doesn't exist, which is expected when parsing the "old" lockfile
         # the first time a new lockfile is generated.
         return None
+
+
+@rule_helper
+async def _parse_lockfile_content(content: bytes, url: str) -> FrozenDict[str, Any] | None:
+    try:
+        parsed_lockfile = json.loads(content)
+        return FrozenDict.deep_freeze(parsed_lockfile)
     except json.JSONDecodeError as e:
-        file_path = (
-            lockfile.file_path if isinstance(lockfile, Lockfile) else lockfile.file_content.path
-        )
-        logger.debug(f"{file_path}: Failed to parse lockfile contents: {e}")
+        logger.debug(f"{url}: Failed to parse lockfile contents: {e}")
         return None
 
 
 @rule_helper
 async def _generate_python_lockfile_diff(
     digest: Digest, resolve_name: str, path: str
 ) -> LockfileDiff:
-    new_content = await Get(DigestContents, Digest, digest)
-    new = await _parse_lockfile(
-        LockfileContent(
-            file_content=next(c for c in new_content if c.path == path),
-            resolve_name=resolve_name,
-        )
-    )
+    new_digest_contents = await Get(DigestContents, Digest, digest)
+    new_content = next(c for c in new_digest_contents if c.path == path).content
+    new_content = strip_comments_from_pex_json_lockfile(new_content)
+    new = await _parse_lockfile_content(new_content, path)
     old = await _parse_lockfile(
         Lockfile(
-            file_path=path,
-            file_path_description_of_origin="generated lockfile",
+            url=path,
+            url_description_of_origin="existing lockfile",
             resolve_name=resolve_name,
         )
     )

src/python/pants/backend/python/util_rules/pex.py

@@ -37,7 +37,6 @@
     EntireLockfile,
     LoadedLockfile,
     LoadedLockfileRequest,
-    Lockfile,
 )
 from pants.backend.python.util_rules.pex_requirements import (
     PexRequirements as PexRequirements,  # Explicit re-export.
@@ -617,10 +616,7 @@ def _build_pex_description(request: PexRequest) -> str:
 
     if isinstance(request.requirements, EntireLockfile):
         lockfile = request.requirements.lockfile
-        if isinstance(lockfile, Lockfile):
-            desc_suffix = f"from {lockfile.file_path}"
-        else:
-            desc_suffix = f"from {lockfile.file_content.path}"
+        desc_suffix = f"from {lockfile.url}"
     else:
         if not request.requirements.req_strings:
             return f"Building {request.output_filename}"

src/python/pants/backend/python/util_rules/pex_from_targets.py

@@ -279,8 +279,8 @@ def maybe_get_resolve(t: Target) -> str | None:
     return ChosenPythonResolve(
         name=chosen_resolve,
         lockfile=Lockfile(
-            file_path=python_setup.resolves[chosen_resolve],
-            file_path_description_of_origin=(
+            url=python_setup.resolves[chosen_resolve],
+            url_description_of_origin=(
                 f"the resolve `{chosen_resolve}` (from `[python].resolves`)"
             ),
             resolve_name=chosen_resolve,
@@ -568,7 +568,7 @@ async def get_repository_pex(
         PexRequest(
             description=softwrap(
                 f"""
-                Installing {chosen_resolve.lockfile.file_path} for the resolve
+                Installing {chosen_resolve.lockfile.url} for the resolve
                 `{chosen_resolve.name}`
                 """
             ),