diff options
Diffstat (limited to 'lib/fileset/internal.nix')
| -rw-r--r-- | lib/fileset/internal.nix | 69 |
1 files changed, 56 insertions, 13 deletions
diff --git a/lib/fileset/internal.nix b/lib/fileset/internal.nix index 2c329edb390d6..b3dbc5b33dc3f 100644 --- a/lib/fileset/internal.nix +++ b/lib/fileset/internal.nix @@ -28,6 +28,7 @@ let drop elemAt filter + findFirst findFirstIndex foldl' head @@ -64,7 +65,7 @@ rec { # - Increment this version # - Add an additional migration function below # - Update the description of the internal representation in ./README.md - _currentVersion = 2; + _currentVersion = 3; # Migrations between versions. The 0th element converts from v0 to v1, and so on migrations = [ @@ -89,8 +90,34 @@ rec { _internalVersion = 2; } ) + + # Convert v2 into v3: filesetTree's now have a representation for an empty file set without a base path + ( + filesetV2: + filesetV2 // { + # All v1 file sets are not the new empty file set + _internalIsEmptyWithoutBase = false; + _internalVersion = 3; + } + ) ]; + _noEvalMessage = '' + lib.fileset: Directly evaluating a file set is not supported. Use `lib.fileset.toSource` to turn it into a usable source instead.''; + + # The empty file set without a base path + _emptyWithoutBase = { + _type = "fileset"; + + _internalVersion = _currentVersion; + + # The one and only! + _internalIsEmptyWithoutBase = true; + + # Double __ to make it be evaluated and ordered first + __noEval = throw _noEvalMessage; + }; + # Create a fileset, see ./README.md#fileset # Type: path -> filesetTree -> fileset _create = base: tree: @@ -103,14 +130,15 @@ rec { _type = "fileset"; _internalVersion = _currentVersion; + + _internalIsEmptyWithoutBase = false; _internalBase = base; _internalBaseRoot = parts.root; _internalBaseComponents = components parts.subpath; _internalTree = tree; # Double __ to make it be evaluated and ordered first - __noEval = throw '' - lib.fileset: Directly evaluating a file set is not supported. Use `lib.fileset.toSource` to turn it into a usable source instead.''; + __noEval = throw _noEvalMessage; }; # Coerce a value to a fileset, erroring when the value cannot be coerced. @@ -155,14 +183,20 @@ rec { _coerce "${functionContext}: ${context}" value ) list; - firstBaseRoot = (head filesets)._internalBaseRoot; + # Find the first value with a base, there may be none! + firstWithBase = findFirst (fileset: ! fileset._internalIsEmptyWithoutBase) null filesets; + # This value is only accessed if first != null + firstBaseRoot = firstWithBase._internalBaseRoot; # Finds the first element with a filesystem root different than the first element, if any differentIndex = findFirstIndex (fileset: - firstBaseRoot != fileset._internalBaseRoot + # The empty value without a base doesn't have a base path + ! fileset._internalIsEmptyWithoutBase + && firstBaseRoot != fileset._internalBaseRoot ) null filesets; in - if differentIndex != null then + # Only evaluates `differentIndex` if there are any elements with a base + if firstWithBase != null && differentIndex != null then throw '' ${functionContext}: Filesystem roots are not the same: ${(head list).context}: root "${toString firstBaseRoot}" @@ -311,7 +345,7 @@ rec { # Special case because the code below assumes that the _internalBase is always included in the result # which shouldn't be done when we have no files at all in the base # This also forces the tree before returning the filter, leads to earlier error messages - if tree == null then + if fileset._internalIsEmptyWithoutBase || tree == null then empty else nonEmpty; @@ -321,7 +355,12 @@ rec { # Type: [ Fileset ] -> Fileset _unionMany = filesets: let - first = head filesets; + # All filesets that have a base, aka not the ones that are the empty value without a base + filesetsWithBase = filter (fileset: ! fileset._internalIsEmptyWithoutBase) filesets; + + # The first fileset that has a base. + # This value is only accessed if there are at all. + firstWithBase = head filesetsWithBase; # To be able to union filesetTree's together, they need to have the same base path. # Base paths can be unioned by taking their common prefix, @@ -332,14 +371,14 @@ rec { # so this cannot cause a stack overflow due to a build-up of unevaluated thunks. commonBaseComponents = foldl' (components: el: commonPrefix components el._internalBaseComponents) - first._internalBaseComponents + firstWithBase._internalBaseComponents # We could also not do the `tail` here to avoid a list allocation, # but then we'd have to pay for a potentially expensive # but unnecessary `commonPrefix` call - (tail filesets); + (tail filesetsWithBase); # The common base path assembled from a filesystem root and the common components - commonBase = append first._internalBaseRoot (join commonBaseComponents); + commonBase = append firstWithBase._internalBaseRoot (join commonBaseComponents); # A list of filesetTree's that all have the same base path # This is achieved by nesting the trees into the components they have over the common base path @@ -351,14 +390,18 @@ rec { setAttrByPath (drop (length commonBaseComponents) fileset._internalBaseComponents) fileset._internalTree - ) filesets; + ) filesetsWithBase; # Folds all trees together into a single one using _unionTree # We do not use a fold here because it would cause a thunk build-up # which could cause a stack overflow for a large number of trees resultTree = _unionTrees trees; in - _create commonBase resultTree; + # If there's no values with a base, we have no files + if filesetsWithBase == [ ] then + _emptyWithoutBase + else + _create commonBase resultTree; # The union of multiple filesetTree's with the same base path. # Later elements are only evaluated if necessary. |