lib: split merge out of the toplevel
This commit is contained in:
@@ -1,11 +1,16 @@
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{ lib, ... }@moduleArgs:
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rec {
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let
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sane-lib = rec {
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feeds = import ./feeds.nix moduleArgs;
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fs = import ./fs.nix moduleArgs;
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merge = import ./merge.nix ({ inherit sane-lib; } // moduleArgs);
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path = import ./path.nix moduleArgs;
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types = import ./types.nix moduleArgs;
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# re-exports
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inherit (merge) mergeTopLevel mkTypedMerge;
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# like `builtins.listToAttrs` but any duplicated `name` throws error on access.
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# Type: listToDisjointAttrs :: [{ name :: String, value :: Any }] -> AttrSet
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listToDisjointAttrs = l: flattenAttrsets (builtins.map nameValueToAttrs l);
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@@ -46,6 +51,10 @@ rec {
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mapToAttrs = f: list: listToDisjointAttrs (builtins.map f list);
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# flatten a nested AttrSet into a list of { path = [String]; value } items.
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# the output contains only non-attr leafs.
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# so e.g. { a.b = 1; } -> [ { path = ["a" "b"]; value = 1; } ]
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# but e.g. { a.b = {}; } -> []
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#
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# Type: flattenAttrs :: AttrSet[AttrSet|Any] -> [{ path :: String, value :: Any }]
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flattenAttrs = flattenAttrs' [];
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flattenAttrs' = path: value: if builtins.isAttrs value then (
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@@ -59,100 +68,5 @@ rec {
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inherit path value;
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}
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];
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# like `mkMerge`, but tries to do normal attribute merging by default and only creates `mkMerge`
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# entries at the highest point where paths overlap between items.
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mergeTopLevel = l:
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if builtins.length l == 0 then
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lib.mkMerge []
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else if builtins.length l == 1 then
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lib.head l
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else if builtins.all isAttrsNotMerge l then
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# merge each toplevel attribute
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lib.zipAttrsWith (_name: mergeTopLevel) l
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else
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lib.mkMerge l;
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# tests that `i` is a normal attrs, and not something make with `lib.mkMerge`.
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isAttrsNotMerge = i: builtins.isAttrs i && i._type or "" != "merge";
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# type-checked `lib.mkMerge`, intended to be usable at the top of a file.
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# `take` is a function which defines a spec enforced against every item to be merged.
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# for example:
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# take = f: { x = f.x; y.z = f.y.z; };
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# - the output is guaranteed to have an `x` attribute and a `y.z` attribute and nothing else.
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# - each output is a `lib.mkMerge` of the corresponding paths across the input lists.
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# - if an item in the input list defines an attr not captured by `f`, this function will throw.
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#
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# Type: mkTypedMerge :: (Attrs -> Attrs) -> [Attrs] -> Attrs
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mkTypedMerge = take: l:
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let
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pathsToMerge = findTerminalPaths take [];
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merged = builtins.map (p: lib.setAttrByPath p (mergeAtPath p l)) pathsToMerge;
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in
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assert builtins.all (i: assertTakesEveryAttr take i []) l;
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flattenAttrsets merged;
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# `take` is as in mkTypedMerge. this function queries which items `take` is interested in.
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# for example:
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# take = f: { x = f.x; y.z = f.y.z; };
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# - for `path == []` we return the toplevel attr names: [ "x" "y"]
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# - for `path == [ "y" ]` we return [ "z" ]
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# - for `path == [ "x" ]` or `path == [ "y" "z" ]` we return []
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#
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# Type: findSubNames :: (Attrs -> Attrs) -> [String] -> [String]
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findSubNames = take: path:
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let
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# define the current path, but nothing more.
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curLevel = lib.setAttrByPath path {};
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# `take` will either set:
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# - { $path = path } => { $path = {} };
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# - { $path.next = path.next } => { $path = { next = ?; } }
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# so, index $path into the output of `take`,
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# and if it has any attrs that means we're interested in those too.
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nextLevel = lib.getAttrFromPath path (take curLevel);
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in
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builtins.attrNames nextLevel;
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# computes a list of all terminal paths that `take` is interested in,
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# where each path is a list of attr names to descend to reach that terminal.
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# Type: findTerminalPaths :: (Attrs -> Attrs) -> [String] -> [[String]]
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findTerminalPaths = take: path:
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let
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subNames = findSubNames take path;
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in if subNames == [] then
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[ path ]
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else
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let
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terminalsPerChild = builtins.map (name: findTerminalPaths take (path ++ [name])) subNames;
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in
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lib.concatLists terminalsPerChild;
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# merges all present values for the provided path
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# Type: mergeAtPath :: [String] -> [Attrs] -> (lib.mkMerge)
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mergeAtPath = path: l:
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let
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itemsToMerge = builtins.filter (lib.hasAttrByPath path) l;
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in lib.mkMerge (builtins.map (lib.getAttrFromPath path) itemsToMerge);
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# throw if `item` includes any data not wanted by `take`.
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# this is recursive: `path` tracks the current location being checked.
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assertTakesEveryAttr = take: item: path:
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let
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takesSubNames = findSubNames take path;
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itemSubNames = findSubNames (_: item) path;
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unexpectedNames = lib.subtractLists takesSubNames itemSubNames;
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takesEverySubAttr = builtins.all (name: assertTakesEveryAttr take item (path ++ [name])) itemSubNames;
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in
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if takesSubNames == [] then
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# this happens when the user takes this whole subtree: i.e. *all* subnames are accepted.
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true
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else if unexpectedNames != [] then
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let
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p = lib.concatStringsSep "." (path ++ lib.sublist 0 1 unexpectedNames);
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in
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throw ''unexpected entry: ${p}''
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else
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takesEverySubAttr;
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}
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};
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in sane-lib
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99
modules/lib/merge.nix
Normal file
99
modules/lib/merge.nix
Normal file
@@ -0,0 +1,99 @@
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{ lib, sane-lib, ... }:
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rec {
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# like `mkMerge`, but tries to do normal attribute merging by default and only creates `mkMerge`
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# entries at the highest point where paths overlap between items.
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mergeTopLevel = l:
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if builtins.length l == 0 then
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lib.mkMerge []
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else if builtins.length l == 1 then
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lib.head l
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else if builtins.all isAttrsNotMerge l then
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# merge each toplevel attribute
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lib.zipAttrsWith (_name: mergeTopLevel) l
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else
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lib.mkMerge l;
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# tests that `i` is a normal attrs, and not something make with `lib.mkMerge`.
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isAttrsNotMerge = i: builtins.isAttrs i && i._type or "" != "merge";
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# type-checked `lib.mkMerge`, intended to be usable at the top of a file.
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# `take` is a function which defines a spec enforced against every item to be merged.
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# for example:
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# take = f: { x = f.x; y.z = f.y.z; };
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# - the output is guaranteed to have an `x` attribute and a `y.z` attribute and nothing else.
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# - each output is a `lib.mkMerge` of the corresponding paths across the input lists.
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# - if an item in the input list defines an attr not captured by `f`, this function will throw.
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#
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# Type: mkTypedMerge :: (Attrs -> Attrs) -> [Attrs] -> Attrs
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mkTypedMerge = take: l:
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let
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pathsToMerge = findTerminalPaths take [];
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merged = builtins.map (p: lib.setAttrByPath p (mergeAtPath p l)) pathsToMerge;
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in
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assert builtins.all (i: assertTakesEveryAttr take i []) l;
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sane-lib.flattenAttrsets merged;
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# `take` is as in mkTypedMerge. this function queries which items `take` is interested in.
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# for example:
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# take = f: { x = f.x; y.z = f.y.z; };
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# - for `path == []` we return the toplevel attr names: [ "x" "y"]
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# - for `path == [ "y" ]` we return [ "z" ]
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# - for `path == [ "x" ]` or `path == [ "y" "z" ]` we return []
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#
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# Type: findSubNames :: (Attrs -> Attrs) -> [String] -> [String]
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findSubNames = take: path:
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let
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# define the current path, but nothing more.
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curLevel = lib.setAttrByPath path {};
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# `take` will either set:
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# - { $path = path } => { $path = {} };
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# - { $path.next = path.next } => { $path = { next = ?; } }
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# so, index $path into the output of `take`,
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# and if it has any attrs that means we're interested in those too.
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nextLevel = lib.getAttrFromPath path (take curLevel);
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in
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builtins.attrNames nextLevel;
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# computes a list of all terminal paths that `take` is interested in,
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# where each path is a list of attr names to descend to reach that terminal.
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# Type: findTerminalPaths :: (Attrs -> Attrs) -> [String] -> [[String]]
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findTerminalPaths = take: path:
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let
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subNames = findSubNames take path;
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in if subNames == [] then
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[ path ]
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else
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let
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terminalsPerChild = builtins.map (name: findTerminalPaths take (path ++ [name])) subNames;
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in
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lib.concatLists terminalsPerChild;
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# merges all present values for the provided path
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# Type: mergeAtPath :: [String] -> [Attrs] -> (lib.mkMerge)
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mergeAtPath = path: l:
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let
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itemsToMerge = builtins.filter (lib.hasAttrByPath path) l;
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in lib.mkMerge (builtins.map (lib.getAttrFromPath path) itemsToMerge);
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# throw if `item` includes any data not wanted by `take`.
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# this is recursive: `path` tracks the current location being checked.
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assertTakesEveryAttr = take: item: path:
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let
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takesSubNames = findSubNames take path;
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itemSubNames = findSubNames (_: item) path;
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unexpectedNames = lib.subtractLists takesSubNames itemSubNames;
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takesEverySubAttr = builtins.all (name: assertTakesEveryAttr take item (path ++ [name])) itemSubNames;
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in
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if takesSubNames == [] then
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# this happens when the user takes this whole subtree: i.e. *all* subnames are accepted.
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true
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else if unexpectedNames != [] then
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let
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p = lib.concatStringsSep "." (path ++ lib.sublist 0 1 unexpectedNames);
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in
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throw ''unexpected entry: ${p}''
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else
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takesEverySubAttr;
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}
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Reference in New Issue
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