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Last active Jul 13, 2021
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Report for runtime dependencies of a derivation
# These are some helpers for figuring out the derivations attributes of runtime
# dependencies of a derivation, in particular the function `runtimeReport`. At
# the bottom of the file you can see it used on `hello`. Spoiler: glibc is a
# runtime dependency.
# For more info see
#
# https://nmattia.com/posts/2019-10-08-runtime-dependencies.html
# Let's call these "imports". They're functions used throughout the code.
# Nothing interesting here.
with rec
{ pkgs = import <nixpkgs> {};
inherit (pkgs)
closureInfo
runCommandNoCC
writeText
jq
;
inherit (pkgs.lib)
concatLists
concatMap
concatStringsSep
filter
isAttrs
isDerivation
isList
isString
mapAttrsToList
;
inherit (builtins)
genericClosure
hasAttr
toJSON
typeOf
unsafeDiscardStringContext
;
};
let
# Create a "runtime report" of the runtime dependencies of `drv`. A "runtime
# report" is made up of smaller "dependency reports". A "dependency report" is
# a string describing the dependency, made from the dependency's derivation
# attributes. Here we use `mkReport` to make the report of any particular
# dependency.
#
# NOTE: we use the following terms:
#
# * "buildtime" to mean basically any derivation involved in the build of
# `drv`.
# * "buildtime-only" for the "buildtime" dependencies that _are not_
# referenced anymore by `drv`'s store entry.
# * "runtime" for the rest.
#
# The "runtime report" is created in two steps:
#
# * Generate reports for all the _buildtime_ dependencies with
# `buildtimeReports`.
# * Filter out the reports for buildtime-only dependencies.
#
# Most of the "buildtime" reports won't even be used, because most buildtime
# dependencies are buildtime-only dependencies. However Nix does not give us a
# way of retrieving the derivation attributes of runtime dependencies, but we
# can twist its arm to:
#
# * Give us the store paths of runtime dependencies (see `cinfo`).
# * Give us the derivation attributes of all the buildtime dependencies (see
# `buildtimeDerivations`).
#
# Here's the hack: `buildtimeReports` tags the reports with the (expected)
# store path of the "buildtime" dependency, which we cross check against the
# list of runtime store paths. If it's a match, we keep it. Otherwise, we
# discard it.
runtimeReport = drv:
runCommandNoCC "${drv.name}-report" { buildInputs = [ jq ]; }
# XXX: This is to avoid IFD
''
(
echo " ---------------------------------"
echo " | OFFICIAL REPORT |"
echo " | requested by: the lawyers |"
echo " | written by: yours truly |"
echo " | TOP SECRET - TOP SECRET |"
echo " ---------------------------------"
echo
echo "runtime dependencies of ${drv.name}:"
cat ${buildtimeReports drv} |\
jq -r --slurpfile runtime ${cinfo drv} \
' # First, we strip away (path-)duplicates.
unique_by(.path)
# Then we map over each build-time derivation and use `select()`
# to keep only the ones that show up in $runtime
| map( # this little beauty checks if "obj.path" is in "runtime"
select(. as $obj | $runtime | any(.[] | . == $obj.path))
| .report)
| .[]'
) > $out
'';
# Creates reports for all of `drv`'s buildtime dependencies. Each element in
# the list has two fields:
#
# * path = "/nix/store/..."
# * report = "some report based on the dependency's derivation attributes"
buildtimeReports = drv: writeText "${drv.name}-runtime" ( toJSON (
map (obj:
# unsafe: optimization to avoid downloading unused deps
{ # XXX: we discard the context of the dependencies' store paths because
# they're only ever used for lookup. This matters when fetching a
# prebuilt final report -- there's no point downloading all of `drv`'s
# buildtime dependencies.
path = unsafeDiscardStringContext obj.key;
report = mkReport obj.drv;
}
)
(buildtimeDerivations drv) # the heavy lifting is done somewhere else
));
# Returns a list of all of `drv0`'s inputs, a.k.a. buildtime dependencies.
# Elements in the list has two fields:
#
# * key: the store path of the input.
# * drv: the actual derivation object.
#
# There are no guarantees that this will find _all_ inputs, but it works well
# enough in practice.
#
buildtimeDerivations = drv0:
let
# We include all the outputs because they each have different outPaths
drvOutputs = drv:
# XXX: some derivations, like stdenv, don't have "outputs"
if hasAttr "outputs" drv
then map (output: drv.${output}) drv.outputs
else [ drv ];
# Recurse into the derivation attributes to find new derivations
drvDeps = attrs:
mapAttrsToList (k: v:
if isDerivation v then (drvOutputs v)
else if isList v
then concatMap drvOutputs (filter isDerivation v)
else []
) attrs;
in
# Walk through the whole DAG of dependencies, using the `outPath` as an
# index for the elements.
let wrap = drv: { key = drv.outPath ; inherit drv; }; in genericClosure
{ startSet = map wrap (drvOutputs drv0) ;
operator = obj: map wrap
( concatLists (drvDeps obj.drv.drvAttrs) ) ;
};
# make a report. Would could also output a json object and process everything
# later on.
mkReport = drv:
let
license =
if hasAttr "meta" drv && hasAttr "license" drv.meta then
if isList drv.meta.license then
concatStringsSep ", " (
map renderLicense drv.meta.license)
else renderLicense drv.meta.license
else "no license";
maintainer =
if hasAttr "meta" drv && hasAttr "maintainers" drv.meta
then concatStringsSep ", " (map (m: m.name) drv.meta.maintainers)
else "nobody";
in " - ${drv.name} (${license}) maintained by ${maintainer}";
# Basically pretty prints a license
renderLicense = license:
if isAttrs license then license.shortName
else if isString license then license
else abort "no idea how to handle license of type ${typeOf license}";
# This is a wrapper around nixpkgs' `closureInfo`. It produces a JSON file
# containing a list of the store paths of `drv`'s runtime dependencies.
cinfo = drv: runCommandNoCC "${drv.name}-cinfo"
{ buildInputs = [ jq ]; }
# NOTE: we avoid IFD here as well
''
cat ${closureInfo { rootPaths = [ drv ]; }}/store-paths |\
grep -v "^$" |\
jq -R -s -c 'split("\n")' |\
jq -c 'map(select( length > 0 ))' > $out
'';
in runtimeReport pkgs.hello
@CMCDragonkai

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@CMCDragonkai CMCDragonkai commented Aug 11, 2020

Is it possible to extend this to also do things like:

  1. Get a report on all dependencies in the closure.
  2. Get a report on only build dependencies (non-runtime dependencies)
  3. Get a report only on immediate dependencies?
  4. Dependencies that our "program" links to vs packages that only contain executables.
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@CMCDragonkai CMCDragonkai commented Aug 11, 2020

Also what does your XXX mean here? What are you using this notation for in your comments?

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Owner Author

@nmattia nmattia commented Aug 11, 2020

  1. What do you mean of all dependencies? Build time + runtime?
  2. Yes, that's what buildTimeReports does (although maybe you want to filter out the runtime ones?)
  3. Yes, should be straightforward. Instead of traversing the entire DAG, stop at 1-hop from the root.
  4. It's a heads up

Hope that helps!

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@CMCDragonkai CMCDragonkai commented Aug 11, 2020

Dependencies of the entire closure. But I realized you already do that. So only the immediate dependencies means stopping 1 hop from the root.

Right so what about running buildTimeReports and filtering out all the runtime ones...

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@CMCDragonkai CMCDragonkai commented Aug 11, 2020

Could this be turned into an opensource program that we package into nixpkgs? It would be really useful. It could also produce JSON for further analysis.

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