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Diffstat (limited to 'nix/dependency-analyzer/default.nix')
| -rw-r--r-- | nix/dependency-analyzer/default.nix | 258 |
1 files changed, 258 insertions, 0 deletions
diff --git a/nix/dependency-analyzer/default.nix b/nix/dependency-analyzer/default.nix new file mode 100644 index 000000000000..54ff72912ea8 --- /dev/null +++ b/nix/dependency-analyzer/default.nix @@ -0,0 +1,258 @@ +{ lib, depot, pkgs, ... }: + +let + inherit (builtins) unsafeDiscardStringContext appendContext; + + # + # Utilities + # + + # Determine all paths a derivation depends on, i.e. input derivations and + # files imported into the Nix store. + # + # Implementation for Nix < 2.6 is quite hacky at the moment. + # + # Type: str -> [str] + # + # TODO(sterni): clean this up and expose it + directDrvDeps = + if lib.versionAtLeast builtins.nixVersion "2.6" + then + # Since https://github.com/NixOS/nix/pull/1643, Nix apparently »preserves + # string context« through a readFile invocation. This has the side effect + # that it becomes possible to query the actual references a store path has. + # Not a 100% sure this is intended, but _very_ convenient for us here. + drvPath: + # if the passed path is not a derivation we can't necessarily get its + # dependencies, since it may not be representable as a Nix string due to + # NUL bytes, e.g. compressed patch files imported into the Nix store. + if builtins.match "^.+\\.drv$" drvPath == null + then [ ] + else builtins.attrNames (builtins.getContext (builtins.readFile drvPath)) + else + # For Nix < 2.6 we have to rely on HACK, namely grepping for quoted store + # path references in the file. In the future this should be replaced by + # a proper derivation parser. + drvPath: builtins.concatLists ( + builtins.filter builtins.isList ( + builtins.split + "\"(${lib.escapeRegex builtins.storeDir}/[[:alnum:]+._?=-]+.drv)\"" + (builtins.readFile drvPath) + ) + ); + + # Maps a list of derivation to the list of corresponding `drvPath`s. + # + # Type: [drv] -> [str] + drvsToPaths = drvs: + builtins.map (drv: builtins.unsafeDiscardOutputDependency drv.drvPath) drvs; + + # + # Calculate map of direct derivation dependencies + # + + # Create the dependency map entry for a given `drvPath` which mainly includes + # a list of other `drvPath`s it depends on. Additionally we store whether the + # derivation is `known`, i.e. part of the initial list of derivations we start + # generating the map from + # + # Type: bool -> string -> set + drvEntry = known: drvPath: + let + # key may not refer to a store path, … + key = unsafeDiscardStringContext drvPath; + # but we must read from the .drv file. + path = builtins.unsafeDiscardOutputDependency drvPath; + in + { + inherit key; + # trick so we can call listToAttrs directly on the result of genericClosure + name = key; + value = { + deps = directDrvDeps path; + inherit known; + }; + }; + + # Create an attribute set that maps every derivation in the combined + # dependency closure of the list of input derivation paths to every of their + # direct dependencies. Additionally every entry will have set their `known` + # attribute to `true` if it is in the list of input derivation paths. + # + # Type: [str] -> set + plainDrvDepMap = drvPaths: + builtins.listToAttrs ( + builtins.genericClosure { + startSet = builtins.map (drvEntry true) drvPaths; + operator = { value, ... }: builtins.map (drvEntry false) value.deps; + } + ); + + # + # Calculate closest known dependencies in the dependency map + # + + inherit (depot.nix.stateMonad) + after + bind + for_ + get + getAttr + run + setAttr + pure + ; + + # This is an action in stateMonad which expects the (initial) state to have + # been produced by `plainDrvDepMap`. Given a `drvPath`, it calculates a + # `knownDeps` list which holds the `drvPath`s of the closest derivation marked + # as `known` along every edge. This list is inserted into the dependency map + # for `drvPath` and every other derivation in its dependecy closure (unless + # the information was already present). This means that the known dependency + # information for a derivation never has to be recalculated, as long as they + # are part of the same stateful computation. + # + # The upshot is that after calling `insertKnownDeps drvPath`, + # `fmap (builtins.getAttr "knownDeps") (getAttr drvPath)` will always succeed. + # + # Type: str -> stateMonad drvDepMap null + insertKnownDeps = drvPathWithContext: + let + # We no longer need to read from the store, so context is irrelevant, but + # we need to check for attr names which requires the absence of context. + drvPath = unsafeDiscardStringContext drvPathWithContext; + in + bind get (initDepMap: + # Get the dependency map's state before we've done anything to obtain the + # entry we'll be manipulating later as well as its dependencies. + let + entryPoint = initDepMap.${drvPath}; + + # We don't need to recurse if our direct dependencies either have their + # knownDeps list already populated or are known dependencies themselves. + depsPrecalculated = + builtins.partition + (dep: + initDepMap.${dep}.known + || initDepMap.${dep} ? knownDeps + ) + entryPoint.deps; + + # If a direct dependency is known, it goes right to our known dependency + # list. If it is unknown, we can copy its knownDeps list into our own. + initiallyKnownDeps = + builtins.concatLists ( + builtins.map + (dep: + if initDepMap.${dep}.known + then [ dep ] + else initDepMap.${dep}.knownDeps + ) + depsPrecalculated.right + ); + in + + # If the information was already calculated before, we can exit right away + if entryPoint ? knownDeps + then pure null + else + after + # For all unknown direct dependencies which don't have a `knownDeps` + # list, we call ourselves recursively to populate it. Since this is + # done sequentially in the state monad, we avoid recalculating the + # list for the same derivation multiple times. + (for_ + depsPrecalculated.wrong + insertKnownDeps) + # After this we can obtain the updated dependency map which will have + # a `knownDeps` list for all our direct dependencies and update the + # entry for the input `drvPath`. + (bind + get + (populatedDepMap: + (setAttr drvPath (entryPoint // { + knownDeps = + lib.unique ( + initiallyKnownDeps + ++ builtins.concatLists ( + builtins.map + (dep: populatedDepMap.${dep}.knownDeps) + depsPrecalculated.wrong + ) + ); + })))) + ); + + # This function puts it all together and is exposed via `__functor`. + # + # For a list of `drvPath`s, calculate an attribute set which maps every + # `drvPath` to a set of the following form: + # + # { + # known = true /* if it is in the list of input derivation paths */; + # deps = [ + # /* list of derivation paths it depends on directly */ + # ]; + # knownDeps = [ + # /* list of the closest derivation paths marked as known this + # derivation depends on. + # */ + # ]; + # } + knownDrvDepMap = knownDrvPaths: + run + (plainDrvDepMap knownDrvPaths) + (after + (for_ + knownDrvPaths + insertKnownDeps) + get); + + # + # Other things based on knownDrvDepMap + # + + # Create a SVG visualizing `knownDrvDepMap`. Nodes are identified by derivation + # name, so multiple entries can be collapsed if they have the same name. + # + # Type: [drv] -> drv + knownDependencyGraph = name: drvs: + let + justName = drvPath: + builtins.substring + (builtins.stringLength builtins.storeDir + 1 + 32 + 1) + (builtins.stringLength drvPath) + (unsafeDiscardStringContext drvPath); + + gv = pkgs.writeText "${name}-dependency-analysis.gv" '' + digraph depot { + ${ + (lib.concatStringsSep "\n" + (lib.mapAttrsToList (name: value: + if !value.known then "" + else lib.concatMapStringsSep "\n" + (knownDep: " \"${justName name}\" -> \"${justName knownDep}\"") + value.knownDeps + ) + (depot.nix.dependency-analyzer ( + drvsToPaths drvs + )))) + } + } + ''; + in + + pkgs.runCommand "${name}-dependency-analysis.svg" + { + nativeBuildInputs = [ + pkgs.buildPackages.graphviz + ]; + } + "dot -Tsvg < ${gv} > $out"; +in + +{ + __functor = _: knownDrvDepMap; + + inherit knownDependencyGraph plainDrvDepMap drvsToPaths; +} |