From 5e3e6fecf3498f2544bb5927e51a9e6ce39ff43b Mon Sep 17 00:00:00 2001
From: Timothy DeHerrera <tim@nrdxp.dev>
Date: Wed, 28 Dec 2022 20:53:43 -0700
Subject: [PATCH] nix-store: implement --query --uncached

Resolves #3946 by providing an efficient means of querying cache status
of the passed paths.

For every path passed, it will be returned on standard output only if it
is not available in any of the configured substituters.
---
 doc/manual/src/command-ref/nix-store.md | 16 +++++++++++-
 src/nix-store/nix-store.cc              | 34 +++++++++++++++++++++++--
 2 files changed, 47 insertions(+), 3 deletions(-)

diff --git a/doc/manual/src/command-ref/nix-store.md b/doc/manual/src/command-ref/nix-store.md
index b712a74635ee..e6dcb4c86f36 100644
--- a/doc/manual/src/command-ref/nix-store.md
+++ b/doc/manual/src/command-ref/nix-store.md
@@ -281,7 +281,7 @@ error: cannot delete path `/nix/store/zq0h41l75vlb4z45kzgjjmsjxvcv1qk7-mesa-6.4'
   {`--outputs` | `--requisites` | `-R` | `--references` |
   `--referrers` | `--referrers-closure` | `--deriver` | `-d` |
   `--graph` | `--tree` | `--binding` *name* | `-b` *name* | `--hash` |
-  `--size` | `--roots`}
+  `--size` | `--roots` | `--uncached` | `-U`}
   [`--use-output`] [`-u`] [`--force-realise`] [`-f`]
   *paths…*
 
@@ -397,6 +397,10 @@ symlink.
     Prints the garbage collector roots that point, directly or
     indirectly, at the store paths *paths*.
 
+  - `--uncached`; `-U`\
+    Outputs a list of the store paths *paths* which are not available in
+    any configured caches.
+
 ## Examples
 
 Print the closure (runtime dependencies) of the `svn` program in the
@@ -435,6 +439,16 @@ $ nix-store -q --tree $(nix-store -qd $(which svn))
 ...
 ```
 
+Show uncached build & runtime dependencies:
+
+```console
+$ drv=$(nix-store -qd $(which svn))
+$ nix-store -qU $(nix-store -qR --include-outputs $drv)
+/nix/store/5mbglq5ldqld8sj57273aljwkfvj22mc-subversion-1.1.4
+/nix/store/9lz9yc6zgmc0vlqmn2ipcpkjlmbi51vv-glibc-2.3.4
+...
+```
+
 Show all paths that depend on the same OpenSSL library as `svn`:
 
 ```console
diff --git a/src/nix-store/nix-store.cc b/src/nix-store/nix-store.cc
index 3bbefedbe07d..27e93024ad8b 100644
--- a/src/nix-store/nix-store.cc
+++ b/src/nix-store/nix-store.cc
@@ -15,6 +15,8 @@
 #include "graphml.hh"
 #include "legacy.hh"
 #include "path-with-outputs.hh"
+#include "filetransfer.hh"
+#include "thread-pool.hh"
 
 #include <iostream>
 #include <algorithm>
@@ -24,6 +26,8 @@
 #include <sys/stat.h>
 #include <fcntl.h>
 
+#include <nlohmann/json.hpp>
+
 
 namespace nix_store {
 
@@ -276,7 +280,7 @@ static void opQuery(Strings opFlags, Strings opArgs)
     enum QueryType
         { qDefault, qOutputs, qRequisites, qReferences, qReferrers
         , qReferrersClosure, qDeriver, qBinding, qHash, qSize
-        , qTree, qGraph, qGraphML, qResolve, qRoots };
+        , qTree, qGraph, qGraphML, qResolve, qRoots, qUncached };
     QueryType query = qDefault;
     bool useOutput = false;
     bool includeOutputs = false;
@@ -300,6 +304,7 @@ static void opQuery(Strings opFlags, Strings opArgs)
         }
         else if (i == "--hash") query = qHash;
         else if (i == "--size") query = qSize;
+        else if (i == "--uncached" || i == "-U") query = qUncached;
         else if (i == "--tree") query = qTree;
         else if (i == "--graph") query = qGraph;
         else if (i == "--graphml") query = qGraphML;
@@ -364,6 +369,32 @@ static void opQuery(Strings opFlags, Strings opArgs)
             }
             break;
 
+        case qUncached: {
+            if (opArgs.empty()) throw UsageError("no paths passed");
+
+            ThreadPool pool(fileTransferSettings.httpConnections);
+
+            std::function<void(StorePath)> queryPath;
+            queryPath = [&](const StorePath & req) {
+                SubstitutablePathInfos infos;
+                store->querySubstitutablePathInfos({{req, std::nullopt}}, infos);
+
+                if (infos.empty()) {
+                    cout << store->printStorePath(req) << '\n';
+                }
+            };
+
+            for (auto & i : opArgs) {
+                auto path = store->followLinksToStorePath(i);
+
+                pool.enqueue(std::bind(queryPath, path));
+            }
+
+            pool.process();
+
+            break;
+        }
+
         case qBinding:
             for (auto & i : opArgs) {
                 auto path = useDeriver(store->followLinksToStorePath(i));
@@ -680,7 +711,6 @@ static void opExport(Strings opFlags, Strings opArgs)
     sink.flush();
 }
 
-
 static void opImport(Strings opFlags, Strings opArgs)
 {
     for (auto & i : opFlags)