Merge pull request #7594 from nrdxp/paths-from-stdin

feat: read installable paths from stdin

doc/manual/src/command-ref/nix-store.md

@@ -54,6 +54,11 @@ have an effect.
     created by sequentially numbering symlinks beyond the first one
     (e.g., `foo`, `foo-2`, `foo-3`, and so on).
 
+  - <span id="opt-stdin">[`--stdin`](#opt-stdin)</span>
+
+    Read *paths…* from the standard input.
+    Useful for chaining nix-store commands.
+
 # Operation `--realise`
 
 ## Synopsis

doc/manual/src/release-notes/rl-next.md

@@ -1,5 +1,9 @@
 # Release X.Y (202?-??-??)
 
+* Commands which take installables on the command line can now read them from the standard input if
+  passed the `--stdin` flag. This is primarily useful when you have a large amount of paths which
+  exceed the OS arg limit.
+
 * The special handling of an [installable](../command-ref/new-cli/nix.md#installables) with `.drv` suffix being interpreted as all of the given [store derivation](../glossary.md#gloss-store-derivation)'s output paths is removed, and instead taken as the literal store path that it represents.
 
   The new `^` syntax for store paths introduced in Nix 2.13 allows explicitly referencing output paths of a derivation.

src/libcmd/command.hh

@@ -128,6 +128,8 @@ struct InstallablesCommand : virtual Args, SourceExprCommand
 
     virtual bool useDefaultInstallables() { return true; }
 
+    bool readFromStdIn;
+
     std::vector<std::string> getFlakesForCompletion() override;
 
 protected:

src/libcmd/installables.cc

@@ -694,6 +694,13 @@ StorePathSet Installable::toDerivations(
 
 InstallablesCommand::InstallablesCommand()
 {
+
+    addFlag({
+        .longName = "stdin",
+        .description = "Read installables from the standard input.",
+        .handler = {&readFromStdIn, true}
+    });
+
     expectArgs({
         .label = "installables",
         .handler = {&_installables},
@@ -710,10 +717,18 @@ void InstallablesCommand::prepare()
 
 Installables InstallablesCommand::load()
 {
-    if (_installables.empty() && useDefaultInstallables())
+    if (_installables.empty() && useDefaultInstallables() && !readFromStdIn)
         // FIXME: commands like "nix profile install" should not have a
         // default, probably.
         _installables.push_back(".");
+
+    if (readFromStdIn && !isatty(STDIN_FILENO)) {
+        std::string word;
+        while (std::cin >> word) {
+            _installables.emplace_back(std::move(word));
+        }
+    }
+
     return parseInstallables(getStore(), _installables);
 }
 

src/nix-store/nix-store.cc

@@ -1020,6 +1020,7 @@ static int main_nix_store(int argc, char * * argv)
     {
         Strings opFlags, opArgs;
         Operation op = 0;
+        bool readFromStdIn;
 
         parseCmdLine(argc, argv, [&](Strings::iterator & arg, const Strings::iterator & end) {
             Operation oldOp = op;
@@ -1078,6 +1079,8 @@ static int main_nix_store(int argc, char * * argv)
                 op = opGenerateBinaryCacheKey;
             else if (*arg == "--add-root")
                 gcRoot = absPath(getArg(*arg, arg, end));
+            else if (*arg == "--stdin" && !isatty(STDIN_FILENO))
+                readFromStdIn = true;
             else if (*arg == "--indirect")
                 ;
             else if (*arg == "--no-output")
@@ -1090,6 +1093,13 @@ static int main_nix_store(int argc, char * * argv)
             else
                 opArgs.push_back(*arg);
 
+            if (readFromStdIn && op != opImport && op != opRestore && op != opServe) {
+                 std::string word;
+                 while (std::cin >> word) {
+                       opArgs.emplace_back(std::move(word));
+                 };
+            }
+
             if (oldOp && oldOp != op)
                 throw UsageError("only one operation may be specified");