Merge pull request #9481 from iFreilicht/disallow-nix-search-without-search-terms

nix search: Disallow empty regex

(cherry picked from commit 1c260fa6d1f47d83954792771d0614db163cc3bc)
Change-Id: Iaaf3605c24a342fcb05d0b534a9f305533d3b5fa

2 files changed, 12 insertions, 9 deletions

diff --git a/src/nix/search.cc b/src/nix/search.cc
index ef0139e09..97ef1375e 100644
--- a/src/nix/search.cc
+++ b/src/nix/search.cc
@@ -67,11 +67,9 @@ struct CmdSearch : InstallableValueCommand, MixJSON
         settings.readOnlyMode = true;
         evalSettings.enableImportFromDerivation.setDefault(false);
 
-        // Empty search string should match all packages
-        // Use "^" here instead of ".*" due to differences in resulting highlighting
-        // (see #1893 -- libc++ claims empty search string is not in POSIX grammar)
+        // Recommend "^" here instead of ".*" due to differences in resulting highlighting
         if (res.empty())
-            res.push_back("^");
+            throw UsageError("Must provide at least one regex! To match all packages, use '%s'.", "nix search <installable> ^");
 
         std::vector<std::regex> regexes;
         std::vector<std::regex> excludeRegexes;
diff --git a/src/nix/search.md b/src/nix/search.md
index 0c5d22549..f65ac9b17 100644
--- a/src/nix/search.md
+++ b/src/nix/search.md
@@ -5,7 +5,7 @@ R""(
 * Show all packages in the `nixpkgs` flake:
 
   ```console
-  # nix search nixpkgs
+  # nix search nixpkgs ^
   * legacyPackages.x86_64-linux.AMB-plugins (0.8.1)
     A set of ambisonics ladspa plugins
 
@@ -34,7 +34,7 @@ R""(
 * Show all packages in the flake in the current directory:
 
   ```console
-  # nix search
+  # nix search . ^
   ```
 
 * Search for Firefox or Chromium:
@@ -64,11 +64,16 @@ R""(
 
 `nix search` searches [*installable*](./nix.md#installables) (which can be evaluated, that is, a
 flake or Nix expression, but not a store path or store derivation path) for packages whose name or description matches all of the
-regular expressions *regex*.  For each matching package, It prints the
+regular expressions *regex*. For each matching package, It prints the
 full attribute name (from the root of the [installable](./nix.md#installables)), the version
 and the `meta.description` field, highlighting the substrings that
-were matched by the regular expressions. If no regular expressions are
-specified, all packages are shown.
+were matched by the regular expressions.
+
+To show all packages, use the regular expression `^`. In contrast to `.*`,
+it avoids highlighting the entire name and description of every package.
+
+> Note that in this context, `^` is the regex character to match the beginning of a string, *not* the delimiter for
+> [selecting a derivation output](@docroot@/command-ref/new-cli/nix.md#derivation-output-selection).
 
 # Flake output attributes