Prefactor: Move get_hash from docker backend to strutil (Cherry-p…

…ick of #18715) (#18738)

Prefactor for #18708

src/python/pants/backend/docker/util_rules/docker_build_context.py

@@ -21,7 +21,7 @@
     DockerBuildEnvironmentError,
     DockerBuildEnvironmentRequest,
 )
-from pants.backend.docker.utils import get_hash, suggest_renames
+from pants.backend.docker.utils import suggest_renames
 from pants.backend.docker.value_interpolation import DockerBuildArgsInterpolationValue
 from pants.backend.shell.target_types import ShellSourceField
 from pants.core.goals.package import BuiltPackage, EnvironmentAwarePackageRequest, PackageFieldSet
@@ -44,7 +44,7 @@
 )
 from pants.engine.unions import UnionRule
 from pants.util.meta import classproperty
-from pants.util.strutil import softwrap
+from pants.util.strutil import softwrap, stable_hash
 from pants.util.value_interpolation import InterpolationContext, InterpolationValue
 
 logger = logging.getLogger(__name__)
@@ -130,7 +130,7 @@ def create(
         # Data from Pants.
         interpolation_context["pants"] = {
             # Present hash for all inputs that can be used for image tagging.
-            "hash": get_hash((build_args, build_env, snapshot.digest)).hexdigest(),
+            "hash": stable_hash((build_args, build_env, snapshot.digest)).hexdigest(),
         }
 
         # Base image tags values for all stages (as parsed from the Dockerfile instructions).

src/python/pants/backend/docker/util_rules/docker_build_context_test.py

@@ -155,7 +155,7 @@ def test_pants_hash(rule_runner: RuleRunner) -> None:
                 "stage0": "latest",
             },
             "build_args": {},
-            "pants": {"hash": "fd19488a9b08a0184432762cab85f1370904d09bafd9df1a2f8a94614b2b7eb6"},
+            "pants": {"hash": "87e90685c07ac302bbff8f9d846b4015621255f741008485fd3ce72253ce54f4"},
         },
     )
 

src/python/pants/backend/docker/utils.py

@@ -4,14 +4,9 @@
 from __future__ import annotations
 
 import difflib
-import hashlib
-import json
 import os.path
-from collections import abc
-from dataclasses import asdict, is_dataclass
 from fnmatch import fnmatch
-from functools import partial
-from typing import Any, Callable, Iterable, Iterator, Sequence, TypeVar
+from typing import Callable, Iterable, Iterator, Sequence, TypeVar
 
 from pants.help.maybe_color import MaybeColor
 from pants.util.ordered_set import FrozenOrderedSet
@@ -169,30 +164,3 @@ def format_rename_suggestion(src_path: str, dst_path: str, *, colors: bool) -> s
     rem = color.maybe_red(src_path)
     add = color.maybe_green(dst_path)
     return f"{rem} => {add}"
-
-
-class JsonEncoder(json.JSONEncoder):
-    """Allow us to serialize everything, with a fallback on `str()` in case of any esoteric
-    types."""
-
-    def default(self, o):
-        """Return a serializable object for o."""
-        if is_dataclass(o):
-            return asdict(o)
-        if isinstance(o, abc.Mapping):
-            return dict(o)
-        if isinstance(o, abc.Sequence):
-            return list(o)
-        try:
-            return super().default(o)
-        except TypeError:
-            return str(o)
-
-
-json_dumps = partial(
-    json.dumps, indent=None, separators=(",", ":"), sort_keys=True, cls=JsonEncoder
-)
-
-
-def get_hash(value: Any, *, name: str = "sha256") -> hashlib._Hash:
-    return hashlib.new(name, json_dumps(value).encode("utf-8"))

src/python/pants/backend/docker/utils_test.py

@@ -3,12 +3,9 @@
 
 from __future__ import annotations
 
-from dataclasses import dataclass
-
 import pytest
 
-from pants.backend.docker.utils import format_rename_suggestion, get_hash, suggest_renames
-from pants.util.frozendict import FrozenDict
+from pants.backend.docker.utils import format_rename_suggestion, suggest_renames
 
 
 @pytest.mark.parametrize(
@@ -171,19 +168,3 @@ def test_suggest_renames(
 def test_format_rename_suggestion(src: str, dst: str) -> None:
     actual = format_rename_suggestion(src, dst, colors=False)
     assert actual == f"{src} => {dst}"
-
-
-def test_hash() -> None:
-    @dataclass(frozen=True)
-    class Data:
-        mapping: FrozenDict[str, str]
-
-    data = Data(
-        FrozenDict(
-            {alpha: alpha.lower() for alpha in [chr(a) for a in range(ord("A"), ord("Z") + 1)]}
-        )
-    )
-    assert (
-        get_hash(data).hexdigest()
-        == "e4da3c55de6ce98ddcbd5b854ff01f5c8b47fdcb2e10ddd5176505e39a332730"
-    )

src/python/pants/notes/2.16.x.md

@@ -2,6 +2,7 @@
 
 ## What's New
 
+
 ### BUILD files
 
 The new `env` function in BUILD files allows access to environment variables in BUILD files.
@@ -14,6 +15,11 @@ the same syntax as target selectors.
 
 ### Backends
 
+#### Docker
+
+The [`{pants.hash}`](https://www.pantsbuild.org/docs/tagging-docker-images#string-interpolation-using-placeholder-values)
+generation code was changed such that the generated hash for the same input will be different in pants 2.16.
+
 #### Python
 
 The Python backend added or improved support for various tools including:

src/python/pants/util/strutil.py

@@ -3,13 +3,20 @@
 
 from __future__ import annotations
 
+import dataclasses
+import hashlib
+import json
 import re
 import shlex
 import textwrap
-from typing import Callable, Iterable, TypeVar
+from collections import abc
+from typing import Any, Callable, Iterable, TypeVar
 
 from typing_extensions import ParamSpec
 
+from pants.engine.internals.native_engine import Digest
+from pants.util.ordered_set import FrozenOrderedSet, OrderedSet
+
 
 def ensure_binary(text_or_binary: bytes | str) -> bytes:
     if isinstance(text_or_binary, bytes):
@@ -335,3 +342,39 @@ def wrapper(func: Callable[P, R]) -> Callable[P, R]:
         return func
 
     return wrapper
+
+
+class _JsonEncoder(json.JSONEncoder):
+    """Allow us to serialize everything, with a fallback on `str()` in case of any esoteric
+    types."""
+
+    def default(self, o):
+        """Return a serializable object for o."""
+        if isinstance(o, abc.Mapping):
+            return dict(o)
+        if isinstance(o, (abc.Sequence, OrderedSet, FrozenOrderedSet)):
+            return list(o)
+
+        # NB: A quick way to embed the type in the hash so that two objects with the same data but
+        # different types produce different hashes.
+        classname = o.__class__.__name__
+        if dataclasses.is_dataclass(o):
+            return {"__class__.__name__": classname, **dataclasses.asdict(o)}
+        if isinstance(o, (Digest,)):
+            return {"__class__.__name__": classname, "fingerprint": o.fingerprint}
+        return super().default(o)
+
+
+def stable_hash(value: Any, *, name: str = "sha256") -> hashlib._Hash:
+    """Attempts to return a stable hash of the value stable across processes.
+
+    "Stable" here means that if `value` is equivalent in multiple invocations (across multiple
+    processes), it should produce the same hash. To that end, what values are accepted are limited
+    in scope.
+    """
+    return hashlib.new(
+        name,
+        json.dumps(
+            value, indent=None, separators=(",", ":"), sort_keys=True, cls=_JsonEncoder
+        ).encode("utf-8"),
+    )

src/python/pants/util/strutil_test.py

@@ -2,10 +2,12 @@
 # Licensed under the Apache License, Version 2.0 (see LICENSE).
 
 import textwrap
+from dataclasses import dataclass
 from textwrap import dedent
 
 import pytest
 
+from pants.util.frozendict import FrozenDict
 from pants.util.strutil import (
     bullet_list,
     comma_separated_list,
@@ -18,6 +20,7 @@
     path_safe,
     pluralize,
     softwrap,
+    stable_hash,
     strip_prefix,
     strip_v2_chroot_path,
 )
@@ -397,3 +400,19 @@ def show_why_this_is_needed() -> None:
 
     with pytest.raises(AssertionError):
         assert show_why_this_is_needed.__doc__ == "calc 1 + 1 = 2"
+
+
+def test_stable_hash() -> None:
+    @dataclass(frozen=True)
+    class Data:
+        mapping: FrozenDict[str, str]
+
+    data = Data(
+        FrozenDict(
+            {alpha: alpha.lower() for alpha in [chr(a) for a in range(ord("A"), ord("Z") + 1)]}
+        )
+    )
+    assert (
+        stable_hash(data).hexdigest()
+        == "1f2a0caa2588274fa99dc7397c1687dbbe6159be0de646a37ba7af241ecf1add"
+    )