fs.py

# Copyright 2020 Pants project contributors (see CONTRIBUTORS.md).
# Licensed under the Apache License, Version 2.0 (see LICENSE).

from dataclasses import dataclass
from enum import Enum
from typing import TYPE_CHECKING, Iterable, Optional, Tuple

from pants.engine.collection import Collection
from pants.engine.rules import RootRule, side_effecting
from pants.util.meta import frozen_after_init

if TYPE_CHECKING:
    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.
    """

    fingerprint: str
    serialized_bytes_length: int


@dataclass(frozen=True)
class Snapshot:
    """A Snapshot is a collection of sorted file paths and dir paths fingerprinted by their
    names/content.

    You can lift a `Digest` to a `Snapshot` with `await Get(Snapshot, Digest, my_digest)`.
    """

    digest: Digest
    files: Tuple[str, ...]
    dirs: Tuple[str, ...]


@dataclass(frozen=True)
class FileContent:
    """The content of a file."""

    path: str
    content: bytes
    is_executable: bool = False

    def __repr__(self) -> str:
        return (
            f"FileContent(path={self.path}, content=(len:{len(self.content)}), "
            f"is_executable={self.is_executable})"
        )


class DigestContents(Collection[FileContent]):
    """The file contents of a Digest."""


class CreateDigest(Collection[FileContent]):
    """A request to create a Digest with the input FileContent values.

    This does _not_ actually materialize the digest to the build root. You must use
    `engine.fs.Workspace` in a `@goal_rule` to save the resulting digest to disk.
    """


class GlobMatchErrorBehavior(Enum):
    """Describe the action to perform when matching globs in BUILD files to source files.

    NB: this object is interpreted from within Snapshot::lift_path_globs() -- that method will need to
    be aware of any changes to this object's definition.
    """

    ignore = "ignore"
    warn = "warn"
    error = "error"


class GlobExpansionConjunction(Enum):
    """Describe whether to require that only some or all glob strings match in a target's sources.

    NB: this object is interpreted from within Snapshot::lift_path_globs() -- that method will need to
    be aware of any changes to this object's definition.
    """

    any_match = "any_match"
    all_match = "all_match"


@frozen_after_init
@dataclass(unsafe_hash=True)
class PathGlobs:
    globs: Tuple[str, ...]
    glob_match_error_behavior: GlobMatchErrorBehavior
    conjunction: GlobExpansionConjunction
    description_of_origin: str

    def __init__(
        self,
        globs: Iterable[str],
        glob_match_error_behavior: GlobMatchErrorBehavior = GlobMatchErrorBehavior.ignore,
        conjunction: GlobExpansionConjunction = GlobExpansionConjunction.any_match,
        description_of_origin: Optional[str] = None,
    ) -> None:
        """A request to find files given a set of globs.

        The syntax supported is roughly Git's glob syntax. Use `*` for globs, `**` for recursive
        globs, and `!` for ignores.

        :param globs: globs to match, e.g. `foo.txt` or `**/*.txt`. To exclude something, prefix it
            with `!`, e.g. `!ignore.py`.
        :param glob_match_error_behavior: whether to warn or error upon match failures
        :param conjunction: whether all `globs` must match or only at least one must match
        :param description_of_origin: a human-friendly description of where this PathGlobs request
            is coming from, used to improve the error message for unmatched globs. For example,
            this might be the text string "the option `--isort-config`".
        """

        # NB: this object is interpreted from within Snapshot::lift_path_globs() -- that method
        # will need to be aware of any changes to this object's definition.
        self.globs = tuple(sorted(globs))
        self.glob_match_error_behavior = glob_match_error_behavior
        self.conjunction = conjunction
        self.description_of_origin = description_of_origin or ""
        self.__post_init__()

    def __post_init__(self) -> None:
        if self.glob_match_error_behavior == GlobMatchErrorBehavior.ignore:
            if self.description_of_origin:
                raise ValueError(
                    "You provided a `description_of_origin` value when `glob_match_error_behavior` "
                    "is set to `ignore`. The `ignore` value means that the engine will never "
                    "generate an error when the globs are generated, so `description_of_origin` "
                    "won't end up ever being used. Please either change "
                    "`glob_match_error_behavior` to `warn` or `error`, or remove "
                    "`description_of_origin`."
                )
        else:
            if not self.description_of_origin:
                raise ValueError(
                    "Please provide a `description_of_origin` so that the error message is more "
                    "helpful to users when their globs fail to match."
                )


@dataclass(frozen=True)
class PathGlobsAndRoot:
    """A set of PathGlobs to capture relative to some root (which may exist outside of the
    buildroot).

    If the `digest_hint` is set, it must be the Digest that we would expect to get if we were to
    expand and Digest the globs. The hint is an optimization that allows for bypassing filesystem
    operations in cases where the expected Digest is known, and the content for the Digest is
    already stored.
    """

    path_globs: PathGlobs
    root: str
    digest_hint: Optional[Digest] = None


@dataclass(frozen=True)
class DigestSubset:
    """A request to get a subset of a digest.

    Example:

        result = await Get(Digest, DigestSubset(original_digest, PathGlobs(["subdir1", "f.txt"]))
    """

    digest: Digest
    globs: PathGlobs


@dataclass(unsafe_hash=True)
class MergeDigests:
    digests: Tuple[Digest, ...]

    def __init__(self, digests: Iterable[Digest]) -> None:
        """A request to merge several digests into one single digest.

        This will fail if there are any conflicting changes, such as two digests having the same
        file but with different content.

        Example:

            result = await Get(Digest, MergeDigests([digest1, digest2])
        """
        self.digests = tuple(digests)


@dataclass(frozen=True)
class RemovePrefix:
    """A request to remove the specified prefix path from every file and directory in the digest.

    This will fail if there are any files or directories in the original input digest without the
    specified digest.

    Example:

        result = await Get(Digest, RemovePrefix(input_digest, "my_dir")
    """

    digest: Digest
    prefix: str


@dataclass(frozen=True)
class AddPrefix:
    """A request to add the specified prefix path to every file and directory in the digest.

    Example:

        result = await Get(Digest, AddPrefix(input_digest, "my_dir")
    """

    digest: Digest
    prefix: str


@dataclass(frozen=True)
class DownloadFile:
    """Download an asset via a GET request.

    To compute the `expected_digest`, manually download the file, then run `shasum -a 256` to
    compute the fingerprint and `wc -c` to compute the expected length of the downloaded file in
    bytes.
    """

    url: str
    expected_digest: Digest


@side_effecting
@dataclass(frozen=True)
class Workspace:
    """A handle for operations that mutate the local filesystem."""

    _scheduler: "SchedulerSession"

    def write_digest(self, digest: Digest, *, path_prefix: Optional[str] = None) -> None:
        """Write a digest to disk, relative to the build root.

        You should not use this in a `for` loop due to slow performance. Instead, call `await
        Get(Digest, MergeDigests)` beforehand.
        """
        self._scheduler.write_digest(digest, path_prefix=path_prefix)


_EMPTY_FINGERPRINT = "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855"
EMPTY_DIGEST = Digest(fingerprint=_EMPTY_FINGERPRINT, serialized_bytes_length=0)
EMPTY_SNAPSHOT = Snapshot(EMPTY_DIGEST, files=(), dirs=())


@dataclass(frozen=True)
class SourcesSnapshot:
    """Sources matched by command line specs.

    `@goal_rule`s may request this when they only need source files to operate and do not need any
    target information. This allows running on files with no owning targets.
    """

    snapshot: Snapshot


def rules():
    return [
        RootRule(Workspace),
        RootRule(CreateDigest),
        RootRule(Digest),
        RootRule(MergeDigests),
        RootRule(PathGlobs),
        RootRule(RemovePrefix),
        RootRule(AddPrefix),
        RootRule(DownloadFile),
        RootRule(DigestSubset),
    ]