diff options
Diffstat (limited to 'lib')
| -rw-r--r-- | lib/attrsets.nix | 115 | ||||
| -rw-r--r-- | lib/default.nix | 5 | ||||
| -rw-r--r-- | lib/lists.nix | 17 | ||||
| -rw-r--r-- | lib/tests/misc.nix | 152 |
4 files changed, 277 insertions, 12 deletions
diff --git a/lib/attrsets.nix b/lib/attrsets.nix index c0d3ede73d0..516fdd8d33f 100644 --- a/lib/attrsets.nix +++ b/lib/attrsets.nix @@ -4,8 +4,8 @@ let inherit (builtins) head tail length; inherit (lib.trivial) id; - inherit (lib.strings) concatStringsSep sanitizeDerivationName; - inherit (lib.lists) foldr foldl' concatMap concatLists elemAt all; + inherit (lib.strings) concatStringsSep concatMapStringsSep escapeNixIdentifier sanitizeDerivationName; + inherit (lib.lists) foldr foldl' concatMap concatLists elemAt all partition groupBy take foldl; in rec { @@ -78,6 +78,103 @@ rec { in attrByPath attrPath (abort errorMsg); + /* Update or set specific paths of an attribute set. + + Takes a list of updates to apply and an attribute set to apply them to, + and returns the attribute set with the updates applied. Updates are + represented as { path = ...; update = ...; } values, where `path` is a + list of strings representing the attribute path that should be updated, + and `update` is a function that takes the old value at that attribute path + as an argument and returns the new + value it should be. + + Properties: + - Updates to deeper attribute paths are applied before updates to more + shallow attribute paths + - Multiple updates to the same attribute path are applied in the order + they appear in the update list + - If any but the last `path` element leads into a value that is not an + attribute set, an error is thrown + - If there is an update for an attribute path that doesn't exist, + accessing the argument in the update function causes an error, but + intermediate attribute sets are implicitly created as needed + + Example: + updateManyAttrsByPath [ + { + path = [ "a" "b" ]; + update = old: { d = old.c; }; + } + { + path = [ "a" "b" "c" ]; + update = old: old + 1; + } + { + path = [ "x" "y" ]; + update = old: "xy"; + } + ] { a.b.c = 0; } + => { a = { b = { d = 1; }; }; x = { y = "xy"; }; } + */ + updateManyAttrsByPath = let + # When recursing into attributes, instead of updating the `path` of each + # update using `tail`, which needs to allocate an entirely new list, + # we just pass a prefix length to use and make sure to only look at the + # path without the prefix length, so that we can reuse the original list + # entries. + go = prefixLength: hasValue: value: updates: + let + # Splits updates into ones on this level (split.right) + # And ones on levels further down (split.wrong) + split = partition (el: length el.path == prefixLength) updates; + + # Groups updates on further down levels into the attributes they modify + nested = groupBy (el: elemAt el.path prefixLength) split.wrong; + + # Applies only nested modification to the input value + withNestedMods = + # Return the value directly if we don't have any nested modifications + if split.wrong == [] then + if hasValue then value + else + # Throw an error if there is no value. This `head` call here is + # safe, but only in this branch since `go` could only be called + # with `hasValue == false` for nested updates, in which case + # it's also always called with at least one update + let updatePath = (head split.right).path; in + throw + ( "updateManyAttrsByPath: Path '${showAttrPath updatePath}' does " + + "not exist in the given value, but the first update to this " + + "path tries to access the existing value.") + else + # If there are nested modifications, try to apply them to the value + if ! hasValue then + # But if we don't have a value, just use an empty attribute set + # as the value, but simplify the code a bit + mapAttrs (name: go (prefixLength + 1) false null) nested + else if isAttrs value then + # If we do have a value and it's an attribute set, override it + # with the nested modifications + value // + mapAttrs (name: go (prefixLength + 1) (value ? ${name}) value.${name}) nested + else + # However if it's not an attribute set, we can't apply the nested + # modifications, throw an error + let updatePath = (head split.wrong).path; in + throw + ( "updateManyAttrsByPath: Path '${showAttrPath updatePath}' needs to " + + "be updated, but path '${showAttrPath (take prefixLength updatePath)}' " + + "of the given value is not an attribute set, so we can't " + + "update an attribute inside of it."); + + # We get the final result by applying all the updates on this level + # after having applied all the nested updates + # We use foldl instead of foldl' so that in case of multiple updates, + # intermediate values aren't evaluated if not needed + in foldl (acc: el: el.update acc) withNestedMods split.right; + + in updates: value: go 0 true value updates; + /* Return the specified attributes from a set. Example: @@ -477,6 +574,20 @@ rec { overrideExisting = old: new: mapAttrs (name: value: new.${name} or value) old; + /* Turns a list of strings into a human-readable description of those + strings represented as an attribute path. The result of this function is + not intended to be machine-readable. + + Example: + showAttrPath [ "foo" "10" "bar" ] + => "foo.\"10\".bar" + showAttrPath [] + => "<root attribute path>" + */ + showAttrPath = path: + if path == [] then "<root attribute path>" + else concatMapStringsSep "." escapeNixIdentifier path; + /* Get a package output. If no output is found, fallback to `.out` and then to the default. diff --git a/lib/default.nix b/lib/default.nix index 3fead03a463..f8ab51c6579 100644 --- a/lib/default.nix +++ b/lib/default.nix @@ -78,9 +78,10 @@ let mapAttrs' mapAttrsToList mapAttrsRecursive mapAttrsRecursiveCond genAttrs isDerivation toDerivation optionalAttrs zipAttrsWithNames zipAttrsWith zipAttrs recursiveUpdateUntil - recursiveUpdate matchAttrs overrideExisting getOutput getBin + recursiveUpdate matchAttrs overrideExisting showAttrPath getOutput getBin getLib getDev getMan chooseDevOutputs zipWithNames zip - recurseIntoAttrs dontRecurseIntoAttrs cartesianProductOfSets; + recurseIntoAttrs dontRecurseIntoAttrs cartesianProductOfSets + updateManyAttrsByPath; inherit (self.lists) singleton forEach foldr fold foldl foldl' imap0 imap1 concatMap flatten remove findSingle findFirst any all count optional optionals toList range partition zipListsWith zipLists diff --git a/lib/lists.nix b/lib/lists.nix index 1dbff7668d7..a030280c8dc 100644 --- a/lib/lists.nix +++ b/lib/lists.nix @@ -4,6 +4,7 @@ let inherit (lib.strings) toInt; inherit (lib.trivial) compare min; + inherit (lib.attrsets) mapAttrs; in rec { @@ -340,15 +341,15 @@ rec { groupBy' builtins.add 0 (x: boolToString (x > 2)) [ 5 1 2 3 4 ] => { true = 12; false = 3; } */ - groupBy' = op: nul: pred: lst: - foldl' (r: e: - let - key = pred e; - in - r // { ${key} = op (r.${key} or nul) e; } - ) {} lst; + groupBy' = op: nul: pred: lst: mapAttrs (name: foldl op nul) (groupBy pred lst); - groupBy = groupBy' (sum: e: sum ++ [e]) []; + groupBy = builtins.groupBy or ( + pred: foldl' (r: e: + let + key = pred e; + in + r // { ${key} = (r.${key} or []) ++ [e]; } + ) {}); /* Merges two lists of the same size together. If the sizes aren't the same the merging stops at the shortest. How both lists are merged is defined diff --git a/lib/tests/misc.nix b/lib/tests/misc.nix index 5fa95828df6..27111903139 100644 --- a/lib/tests/misc.nix +++ b/lib/tests/misc.nix @@ -761,4 +761,156 @@ runTests { { a = 3; b = 30; c = 300; } ]; }; + + # The example from the showAttrPath documentation + testShowAttrPathExample = { + expr = showAttrPath [ "foo" "10" "bar" ]; + expected = "foo.\"10\".bar"; + }; + + testShowAttrPathEmpty = { + expr = showAttrPath []; + expected = "<root attribute path>"; + }; + + testShowAttrPathVarious = { + expr = showAttrPath [ + "." + "foo" + "2" + "a2-b" + "_bc'de" + ]; + expected = ''".".foo."2".a2-b._bc'de''; + }; + + testGroupBy = { + expr = groupBy (n: toString (mod n 5)) (range 0 16); + expected = { + "0" = [ 0 5 10 15 ]; + "1" = [ 1 6 11 16 ]; + "2" = [ 2 7 12 ]; + "3" = [ 3 8 13 ]; + "4" = [ 4 9 14 ]; + }; + }; + + testGroupBy' = { + expr = groupBy' builtins.add 0 (x: boolToString (x > 2)) [ 5 1 2 3 4 ]; + expected = { false = 3; true = 12; }; + }; + + # The example from the updateManyAttrsByPath documentation + testUpdateManyAttrsByPathExample = { + expr = updateManyAttrsByPath [ + { + path = [ "a" "b" ]; + update = old: { d = old.c; }; + } + { + path = [ "a" "b" "c" ]; + update = old: old + 1; + } + { + path = [ "x" "y" ]; + update = old: "xy"; + } + ] { a.b.c = 0; }; + expected = { a = { b = { d = 1; }; }; x = { y = "xy"; }; }; + }; + + # If there are no updates, the value is passed through + testUpdateManyAttrsByPathNone = { + expr = updateManyAttrsByPath [] "something"; + expected = "something"; + }; + + # A single update to the root path is just like applying the function directly + testUpdateManyAttrsByPathSingleIncrement = { + expr = updateManyAttrsByPath [ + { + path = [ ]; + update = old: old + 1; + } + ] 0; + expected = 1; + }; + + # Multiple updates can be applied are done in order + testUpdateManyAttrsByPathMultipleIncrements = { + expr = updateManyAttrsByPath [ + { + path = [ ]; + update = old: old + "a"; + } + { + path = [ ]; + update = old: old + "b"; + } + { + path = [ ]; + update = old: old + "c"; + } + ] ""; + expected = "abc"; + }; + + # If an update doesn't use the value, all previous updates are not evaluated + testUpdateManyAttrsByPathLazy = { + expr = updateManyAttrsByPath [ + { + path = [ ]; + update = old: old + throw "nope"; + } + { + path = [ ]; + update = old: "untainted"; + } + ] (throw "start"); + expected = "untainted"; + }; + + # Deeply nested attributes can be updated without affecting others + testUpdateManyAttrsByPathDeep = { + expr = updateManyAttrsByPath [ + { + path = [ "a" "b" "c" ]; + update = old: old + 1; + } + ] { + a.b.c = 0; + + a.b.z = 0; + a.y.z = 0; + x.y.z = 0; + }; + expected = { + a.b.c = 1; + + a.b.z = 0; + a.y.z = 0; + x.y.z = 0; + }; + }; + + # Nested attributes are updated first + testUpdateManyAttrsByPathNestedBeforehand = { + expr = updateManyAttrsByPath [ + { + path = [ "a" ]; + update = old: old // { x = old.b; }; + } + { + path = [ "a" "b" ]; + update = old: old + 1; + } + ] { + a.b = 0; + }; + expected = { + a.b = 1; + a.x = 1; + }; + }; + } |