# From home-manager: https://github.com/nix-community/home-manager/blob/master/modules/lib/dag.nix # A generalization of Nixpkgs's `strings-with-deps.nix`. # # The main differences from the Nixpkgs version are # # - not specific to strings, i.e., any payload is OK, # # - the addition of the function `entryBefore` indicating a "wanted # by" relationship. {lib}: let inherit (builtins) isAttrs attrValues attrNames elem all head tail length toJSON isString; inherit (lib.attrsets) filterAttrs mapAttrs; inherit (lib.lists) toposort; inherit (lib.nvim.dag) empty isEntry entryBetween entryAfter entriesBetween entryAnywhere topoSort; in { empty = {}; isEntry = e: e ? data && e ? after && e ? before; isDag = dag: isAttrs dag && all isEntry (attrValues dag); /* Takes an attribute set containing entries built by entryAnywhere, entryAfter, and entryBefore to a topologically sorted list of entries. Internally this function uses the `toposort` function in `<nixpkgs/lib/lists.nix>` and its value is accordingly. Specifically, the result on success is { result = [ { name = ?; data = ?; } … ] } For example nix-repl> topoSort { a = entryAnywhere "1"; b = entryAfter [ "a" "c" ] "2"; c = entryBefore [ "d" ] "3"; d = entryBefore [ "e" ] "4"; e = entryAnywhere "5"; } == { result = [ { data = "1"; name = "a"; } { data = "3"; name = "c"; } { data = "2"; name = "b"; } { data = "4"; name = "d"; } { data = "5"; name = "e"; } ]; } true And the result on error is { cycle = [ { after = ?; name = ?; data = ? } … ]; loops = [ { after = ?; name = ?; data = ? } … ]; } For example nix-repl> topoSort { a = entryAnywhere "1"; b = entryAfter [ "a" "c" ] "2"; c = entryAfter [ "d" ] "3"; d = entryAfter [ "b" ] "4"; e = entryAnywhere "5"; } == { cycle = [ { after = [ "a" "c" ]; data = "2"; name = "b"; } { after = [ "d" ]; data = "3"; name = "c"; } { after = [ "b" ]; data = "4"; name = "d"; } ]; loops = [ { after = [ "a" "c" ]; data = "2"; name = "b"; } ]; } true */ topoSort = dag: let dagBefore = dag: name: attrNames (filterAttrs (_n: v: elem name v.before) dag); normalizedDag = mapAttrs (n: v: { name = n; inherit (v) data; after = v.after ++ dagBefore dag n; }) dag; before = a: b: elem a.name b.after; sorted = toposort before (attrValues normalizedDag); in if sorted ? result then { result = map (v: {inherit (v) name data;}) sorted.result; } else sorted; # Applies a function to each element of the given DAG. map = f: mapAttrs (n: v: v // {data = f n v.data;}); entryBetween = before: after: data: {inherit data before after;}; # Create a DAG entry with no particular dependency information. entryAnywhere = entryBetween [] []; entryAfter = entryBetween []; entryBefore = before: entryBetween before []; # Given a list of entries, this function places them in order within the DAG. # Each entry is labeled "${tag}-${entry index}" and other DAG entries can be # added with 'before' or 'after' referring these indexed entries. # # The entries as a whole can be given a relation to other DAG nodes. All # generated nodes are then placed before or after those dependencies. entriesBetween = tag: let go = i: before: after: entries: let name = "${tag}-${toString i}"; in if entries == [] then empty else if length entries == 1 then { "${name}" = entryBetween before after (head entries); } else { "${name}" = entryAfter after (head entries); } // go (i + 1) before [name] (tail entries); in go 0; entriesAnywhere = tag: entriesBetween tag [] []; entriesAfter = tag: entriesBetween tag []; entriesBefore = tag: before: entriesBetween tag before []; # mkLuarcSection and mkVimrcSection take a section DAG # and return a string containing a comment to identify # the section, and the data contained within the section # # all operations are done without any modifications # to the inputted section data mkLuarcSection = section: '' -- SECTION: ${section.name} ${section.data} ''; resolveDag = { name, dag, mapResult, }: let # When the value is a string, default it to dag.entryAnywhere finalDag = mapAttrs (_: value: if isString value then entryAnywhere value else value) dag; sortedDag = topoSort finalDag; result = if sortedDag ? result then mapResult sortedDag.result else abort ("Dependency cycle in ${name}: " + toJSON sortedDag); in result; }