fs.Digest is declared in Rust

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

@@ -7,7 +7,14 @@
 import pytest
 
 from pants.backend.python.goals.coverage_py import CoverageSubsystem, create_coverage_config
-from pants.engine.fs import CreateDigest, Digest, DigestContents, FileContent, PathGlobs
+from pants.engine.fs import (
+    EMPTY_DIGEST,
+    CreateDigest,
+    Digest,
+    DigestContents,
+    FileContent,
+    PathGlobs,
+)
 from pants.testutil.option_util import create_subsystem
 from pants.testutil.rule_runner import MockGet, run_rule_with_mocks
 
@@ -22,7 +29,7 @@ def mock_handle_config(request: CreateDigest) -> Digest:
         assert isinstance(request[0], FileContent)
         assert request[0].is_executable is False
         resolved_config.append(request[0].content.decode())
-        return Digest("jerry", 30)
+        return EMPTY_DIGEST
 
     def mock_read_config(_: PathGlobs) -> DigestContents:
         # This shouldn't be called if no config file provided.
@@ -37,7 +44,7 @@ def mock_read_config(_: PathGlobs) -> DigestContents:
     ]
 
     result = run_rule_with_mocks(create_coverage_config, rule_args=[coverage], mock_gets=mock_gets)
-    assert result.digest.fingerprint == "jerry"
+    assert result.digest.fingerprint == EMPTY_DIGEST.fingerprint
     assert len(resolved_config) == 1
     return resolved_config[0]
 

src/python/pants/core/goals/fmt_test.py

@@ -272,9 +272,10 @@ def test_streaming_output_skip() -> None:
 
 
 def test_streaming_output_changed() -> None:
+    changed_digest = Digest(EMPTY_DIGEST.fingerprint, 2)
     result = FmtResult(
         input=EMPTY_DIGEST,
-        output=Digest("abc", 10),
+        output=changed_digest,
         stdout="stdout",
         stderr="stderr",
         formatter_name="formatter",

src/python/pants/engine/fs.py

@@ -6,6 +6,7 @@
 from typing import TYPE_CHECKING, Iterable, Optional, Tuple, Union
 
 from pants.engine.collection import Collection
+from pants.engine.internals.native_engine import PyDigest
 from pants.engine.rules import QueryRule, side_effecting
 from pants.option.global_options import GlobMatchErrorBehavior as GlobMatchErrorBehavior
 from pants.util.meta import frozen_after_init
@@ -14,16 +15,12 @@
     from pants.engine.internals.scheduler import SchedulerSession
 
 
-@dataclass(frozen=True)
-class Digest:
-    """A Digest is a lightweight reference to a set of files known about by the engine.
-
-    You can use `await Get(Snapshot, Digest)` to set the file names referred to, or use `await
-    Get(DigestContents, Digest)` to see the actual file content.
-    """
+"""A Digest is a lightweight reference to a set of files known about by the engine.
 
-    fingerprint: str
-    serialized_bytes_length: int
+You can use `await Get(Snapshot, Digest)` to set the file names referred to, or use `await
+Get(DigestContents, Digest)` to see the actual file content.
+"""
+Digest = PyDigest
 
 
 @dataclass(frozen=True)

src/python/pants/engine/internals/BUILD

@@ -23,7 +23,10 @@ python_integration_tests(
 
 python_library(
   name='native',
-  sources=['native.py'],
+  sources=[
+    'native.py',
+    'native_engine.pyi',
+  ],
   dependencies=[
     ':native_engine',
   ],

src/python/pants/engine/internals/native.py

@@ -10,7 +10,7 @@
 from pants.base.exiter import ExitCode
 from pants.engine.fs import PathGlobs
 from pants.engine.internals import native_engine
-from pants.engine.internals.native_engine import (  # type: ignore[import]
+from pants.engine.internals.native_engine import (
     PyExecutionRequest,
     PyExecutionStrategyOptions,
     PyExecutor,
@@ -71,18 +71,18 @@ def generator_send(
             if isinstance(res, Get):
                 # Get.
                 return PyGeneratorResponseGet(
-                    res.output_type,
-                    res.input_type,
-                    res.input,
+                    product=res.output_type,
+                    declared_subject=res.input_type,
+                    subject=res.input,
                 )
             elif type(res) in (tuple, list):
                 # GetMulti.
                 return PyGeneratorResponseGetMulti(
-                    tuple(
+                    gets=tuple(
                         PyGeneratorResponseGet(
-                            get.output_type,
-                            get.input_type,
-                            get.input,
+                            product=get.output_type,
+                            declared_subject=get.input_type,
+                            subject=get.input,
                         )
                         for get in res
                     )
@@ -94,7 +94,7 @@ def generator_send(
                 raise
             # This was a `return` from a coroutine, as opposed to a `StopIteration` raised
             # by calling `next()` on an empty iterator.
-            return PyGeneratorResponseBreak(e.value)
+            return PyGeneratorResponseBreak(val=e.value)
 
 
 class RawFdRunner(Protocol):
@@ -211,11 +211,11 @@ def new_session(
         session_values: SessionValues,
     ) -> PySession:
         return PySession(
-            scheduler,
-            dynamic_ui,
-            build_id,
-            should_report_workunits,
-            session_values,
+            scheduler=scheduler,
+            should_render_ui=dynamic_ui,
+            build_id=build_id,
+            should_report_workunits=should_report_workunits,
+            session_values=session_values,
         )
 
     def new_scheduler(
@@ -266,20 +266,23 @@ def new_scheduler(
             local_enable_nailgun=execution_options.process_execution_local_enable_nailgun,
         )
 
-        return self.lib.scheduler_create(
-            self._executor,
-            tasks,
-            types,
-            # Project tree.
-            build_root,
-            local_store_dir,
-            local_execution_root_dir,
-            named_caches_dir,
-            ca_certs_path,
-            ignore_patterns,
-            use_gitignore,
-            remoting_options,
-            exec_stategy_opts,
+        return cast(
+            PyScheduler,
+            self.lib.scheduler_create(
+                self._executor,
+                tasks,
+                types,
+                # Project tree.
+                build_root,
+                local_store_dir,
+                local_execution_root_dir,
+                named_caches_dir,
+                ca_certs_path,
+                ignore_patterns,
+                use_gitignore,
+                remoting_options,
+                exec_stategy_opts,
+            ),
         )
 
     def set_panic_handler(self):

src/python/pants/engine/internals/native_engine.pyi

@@ -0,0 +1,48 @@
+from typing import Any
+
+# TODO: black and flake8 disagree about the content of this file:
+#   see https://github.com/psf/black/issues/1548
+# flake8: noqa: E302
+
+class PyDigest:
+    def __init__(self, fingerprint: str, serialized_bytes_length: int) -> None: ...
+    @property
+    def fingerprint(self) -> str: ...
+    @property
+    def serialized_bytes_length(self) -> int: ...
+
+class PyExecutionRequest:
+    def __init__(self, **kwargs: Any) -> None: ...
+
+class PyExecutionStrategyOptions:
+    def __init__(self, **kwargs: Any) -> None: ...
+
+class PyExecutor:
+    def __init__(self, **kwargs: Any) -> None: ...
+
+class PyGeneratorResponseBreak:
+    def __init__(self, **kwargs: Any) -> None: ...
+
+class PyGeneratorResponseGet:
+    def __init__(self, **kwargs: Any) -> None: ...
+
+class PyGeneratorResponseGetMulti:
+    def __init__(self, **kwargs: Any) -> None: ...
+
+class PyNailgunServer:
+    def __init__(self, **kwargs: Any) -> None: ...
+
+class PyRemotingOptions:
+    def __init__(self, **kwargs: Any) -> None: ...
+
+class PyScheduler:
+    def __init__(self, **kwargs: Any) -> None: ...
+
+class PySession:
+    def __init__(self, **kwargs: Any) -> None: ...
+
+class PyTasks:
+    def __init__(self, **kwargs: Any) -> None: ...
+
+class PyTypes:
+    def __init__(self, **kwargs: Any) -> None: ...

src/python/pants/engine/internals/scheduler.py

@@ -30,7 +30,7 @@
     RemovePrefix,
     Snapshot,
 )
-from pants.engine.internals.native_engine import PyTypes  # type: ignore[import]
+from pants.engine.internals.native_engine import PyTypes
 from pants.engine.internals.nodes import Return, Throw
 from pants.engine.internals.selectors import Params
 from pants.engine.internals.session import SessionValues
@@ -130,7 +130,6 @@ def __init__(
         tasks = self._register_rules(rule_index, union_membership)
 
         types = PyTypes(
-            directory_digest=Digest,
             file_digest=FileDigest,
             snapshot=Snapshot,
             paths=Paths,

src/python/pants/engine/process_test.py

@@ -7,7 +7,15 @@
 
 import pytest
 
-from pants.engine.fs import CreateDigest, Digest, DigestContents, FileContent, PathGlobs, Snapshot
+from pants.engine.fs import (
+    EMPTY_DIGEST,
+    CreateDigest,
+    Digest,
+    DigestContents,
+    FileContent,
+    PathGlobs,
+    Snapshot,
+)
 from pants.engine.internals.scheduler import ExecutionError
 from pants.engine.process import (
     BinaryPathRequest,
@@ -451,7 +459,7 @@ def test_non_fallible_failing_command_raises(self):
 
 
 def test_running_interactive_process_in_workspace_cannot_have_input_files() -> None:
-    mock_digest = Digest("fake", 1)
+    mock_digest = Digest(EMPTY_DIGEST.fingerprint, 1)
     with pytest.raises(ValueError):
         InteractiveProcess(argv=["/bin/echo"], input_digest=mock_digest, run_in_workspace=True)
 

src/rust/engine/hashing/Cargo.toml

@@ -6,6 +6,7 @@ authors = [ "Pants Build <[email protected]>" ]
 publish = false
 
 [dependencies]
+byteorder = "1.3"
 digest = "0.9"
 generic-array = "0.14"
 hex = "0.3.1"

src/rust/engine/hashing/src/lib.rs

@@ -27,6 +27,7 @@
 // Arc<Mutex> can be more clear than needing to grok Orderings:
 #![allow(clippy::mutex_atomic)]
 
+use byteorder::ByteOrder;
 use digest::consts::U32;
 use generic_array::GenericArray;
 use serde::de::{MapAccess, Visitor};
@@ -85,6 +86,14 @@ impl Fingerprint {
     }
     s
   }
+
+  ///
+  /// Using the fact that a Fingerprint is computed using a strong hash function, computes a strong
+  /// but short hash value from a prefix.
+  ///
+  pub fn prefix_hash(&self) -> u64 {
+    byteorder::BigEndian::read_u64(&self.0)
+  }
 }
 
 impl fmt::Display for Fingerprint {