Commit 2035f8a3 authored by Silvan Mosberger's avatar Silvan Mosberger
Browse files

lib.fileset.fileFilter: Don't run predicate unnecessarily 

Before:

    nix-repl> fileset.trace (fileset.fileFilter (file: builtins.trace file.name false) ./default.nix)
    trace: README.md
    trace: benchmark.sh
    trace: default.nix
    trace: internal.nix
    trace: mock-splitRoot.nix
    trace: tests.sh

After:

    nix-repl> fileset.trace (fileset.fileFilter (file: builtins.trace file.name false) ./default.nix)
    trace: default.nix
parent e1d83317

lib/fileset/internal.nix

+23 −16
Original line number Diff line number Diff line
@@ -732,29 +732,36 @@ rec { 
  # Type: ({ name, type, ... } -> Bool) -> FileSet -> FileSet

  _fileFilter = predicate: fileset:

    let

      # Check the predicate for a path and a filesetTree, returning a new filesetTree

      # Type: Path -> filesetTree -> filesetTree

      recurse = path: tree:

        mapAttrs (name: subtree:

          if isAttrs subtree || subtree == "directory" then

            recurse (path + "/${name}") subtree

          else if

      # Check the predicate for a single file

      # Type: String -> String -> filesetTree

      fromFile = name: type:

        if

          predicate {

              inherit name;

              type = subtree;

            inherit name type;

            # To ensure forwards compatibility with more arguments being added in the future,

            # adding an attribute which can't be deconstructed :)

            "lib.fileset.fileFilter: The predicate function passed as the first argument must be able to handle extra attributes for future compatibility. If you're using `{ name, file }:`, use `{ name, file, ... }:` instead." = null;

          }

        then

            subtree

          type

        else

          null;



      # Check the predicate for all files in a directory

      # Type: Path -> filesetTree

      fromDir = path: tree:

        mapAttrs (name: subtree:

          if isAttrs subtree || subtree == "directory" then

            fromDir (path + "/${name}") subtree

          else if subtree == null then

            null

          else

            fromFile name subtree

        ) (_directoryEntries path tree);

    in

    if fileset._internalIsEmptyWithoutBase then

      _emptyWithoutBase

    else

      _create fileset._internalBase

        (recurse fileset._internalBase fileset._internalTree);

        (fromDir fileset._internalBase fileset._internalTree);

}

lib/fileset/tests.sh

+20 −0
Original line number Diff line number Diff line
@@ -857,6 +857,26 @@ checkFileset 'union ./c/a (fileFilter (file: assert file.name != "a"; true) ./.) 
# but here we need to use ./c

checkFileset 'union (fileFilter (file: assert file.name != "a"; true) ./.) ./c'



# Also lazy, the filter isn't called on a filtered out path

tree=(

    [a]=1

    [b]=0

    [c]=0

)

checkFileset 'fileFilter (file: assert file.name != "c"; file.name == "a") (difference ./. ./c)'



# Make sure single files are filtered correctly

tree=(

    [a]=1

    [b]=0

)

checkFileset 'fileFilter (file: assert file.name == "a"; true) ./a'

tree=(

    [a]=0

    [b]=0

)

checkFileset 'fileFilter (file: assert file.name == "a"; false) ./a'



## Tracing



# The second trace argument is returned