nix profile: Allow referring to elements by human-readable name

doc/manual/rl-next/nix-profile-names.md

@@ -0,0 +1,6 @@
+---
+synopsis: "`nix profile` now allows referring to elements by human-readable name"
+prs: 8678
+---
+
+[`nix profile`](@docroot@/command-ref/new-cli/nix3-profile.md) now uses names to refer to installed packages when running [`list`](@docroot@/command-ref/new-cli/nix3-profile-list.md), [`remove`](@docroot@/command-ref/new-cli/nix3-profile-remove.md) or [`upgrade`](@docroot@/command-ref/new-cli/nix3-profile-upgrade.md) as opposed to indices. Indices are deprecated and will be removed in a future version.

src/libexpr/flake/flakeref.cc

@@ -190,7 +190,7 @@ std::optional<std::pair<FlakeRef, std::string>> parseFlakeIdRef(
 
     static std::regex flakeRegex(
         "((" + flakeIdRegexS + ")(?:/(?:" + refAndOrRevRegex + "))?)"
-        + "(?:#(" + queryRegex + "))?",
+        + "(?:#(" + fragmentRegex + "))?",
         std::regex::ECMAScript);
 
     if (std::regex_match(url, match, flakeRegex)) {

src/libutil/url-name.cc

@@ -0,0 +1,48 @@
+#include "url-name.hh"
+#include <regex>
+#include <iostream>
+
+namespace nix {
+
+static const std::string attributeNamePattern("[a-z0-9_-]+");
+static const std::regex lastAttributeRegex("(?:" + attributeNamePattern + "\\.)*(?!default)(" + attributeNamePattern +")(\\^.*)?");
+static const std::string pathSegmentPattern("[a-zA-Z0-9_-]+");
+static const std::regex lastPathSegmentRegex(".*/(" + pathSegmentPattern +")");
+static const std::regex secondPathSegmentRegex("(?:" + pathSegmentPattern + ")/(" + pathSegmentPattern +")(?:/.*)?");
+static const std::regex gitProviderRegex("github|gitlab|sourcehut");
+static const std::regex gitSchemeRegex("git($|\\+.*)");
+static const std::regex defaultOutputRegex(".*\\.default($|\\^.*)");
+
+std::optional<std::string> getNameFromURL(const ParsedURL & url)
+{
+    std::smatch match;
+
+    /* If there is a dir= argument, use its value */
+    if (url.query.count("dir") > 0)
+        return url.query.at("dir");
+
+    /* If the fragment isn't a "default" and contains two attribute elements, use the last one */
+    if (std::regex_match(url.fragment, match, lastAttributeRegex))
+        return match.str(1);
+
+    /* If this is a github/gitlab/sourcehut flake, use the repo name */
+    if (std::regex_match(url.scheme, gitProviderRegex) && std::regex_match(url.path, match, secondPathSegmentRegex))
+        return match.str(1);
+
+    /* If it is a regular git flake, use the directory name */
+    if (std::regex_match(url.scheme, gitSchemeRegex) && std::regex_match(url.path, match, lastPathSegmentRegex))
+        return match.str(1);
+
+    /* If everything failed but there is a non-default fragment, use it in full */
+    if (!url.fragment.empty() && !std::regex_match(url.fragment, defaultOutputRegex))
+        return url.fragment;
+
+    /* If there is no fragment, take the last element of the path */
+    if (std::regex_match(url.path, match, lastPathSegmentRegex))
+        return match.str(1);
+
+    /* If even that didn't work, the URL does not contain enough info to determine a useful name */
+    return {};
+}
+
+}

src/libutil/url-name.hh

@@ -0,0 +1,20 @@
+#include "url.hh"
+#include "url-parts.hh"
+#include "util.hh"
+#include "split.hh"
+
+namespace nix {
+
+/**
+ * Try to extract a reasonably unique and meaningful, human-readable
+ * name of a flake output from a parsed URL.
+ * When nullopt is returned, the callsite should use information available
+ * to it outside of the URL to determine a useful name.
+ * This is a heuristic approach intended for user interfaces.
+ * @return nullopt if the extracted name is not useful to identify a
+ * flake output, for example because it is empty or "default".
+ * Otherwise returns the extracted name.
+ */
+std::optional<std::string> getNameFromURL(const ParsedURL & url);
+
+}

src/libutil/url-parts.hh

@@ -19,6 +19,7 @@ const static std::string userRegex = "(?:(?:" + unreservedRegex + "|" + pctEncod
 const static std::string authorityRegex = "(?:" + userRegex + "@)?" + hostRegex + "(?::[0-9]+)?";
 const static std::string pcharRegex = "(?:" + unreservedRegex + "|" + pctEncoded + "|" + subdelimsRegex + "|[:@])";
 const static std::string queryRegex = "(?:" + pcharRegex + "|[/? \"])*";
+const static std::string fragmentRegex = "(?:" + pcharRegex + "|[/? \"^])*";
 const static std::string segmentRegex = "(?:" + pcharRegex + "*)";
 const static std::string absPathRegex = "(?:(?:/" + segmentRegex + ")*/?)";
 const static std::string pathRegex = "(?:" + segmentRegex + "(?:/" + segmentRegex + ")*/?)";

src/libutil/url.cc

@@ -16,7 +16,7 @@ ParsedURL parseURL(const std::string & url)
         "((" + schemeNameRegex + "):"
         + "(?:(?://(" + authorityRegex + ")(" + absPathRegex + "))|(/?" + pathRegex + ")))"
         + "(?:\\?(" + queryRegex + "))?"
-        + "(?:#(" + queryRegex + "))?",
+        + "(?:#(" + fragmentRegex + "))?",
         std::regex::ECMAScript);
 
     std::smatch match;

src/nix/profile-list.md

@@ -6,12 +6,14 @@ R""(
 
   ```console
   # nix profile list
+  Name:               gdb
   Index:              0
   Flake attribute:    legacyPackages.x86_64-linux.gdb
   Original flake URL: flake:nixpkgs
   Locked flake URL:   github:NixOS/nixpkgs/7b38b03d76ab71bdc8dc325e3f6338d984cc35ca
   Store paths:        /nix/store/indzcw5wvlhx6vwk7k4iq29q15chvr3d-gdb-11.1
 
+  Name:               blender-bin
   Index:              1
   Flake attribute:    packages.x86_64-linux.default
   Original flake URL: flake:blender-bin
@@ -26,18 +28,22 @@ R""(
   # nix build github:edolstra/nix-warez/91f2ffee657bf834e4475865ae336e2379282d34?dir=blender#packages.x86_64-linux.default
   ```
 
-  will build the package with index 1 shown above.
+  will build the package `blender-bin` shown above.
 
 # Description
 
 This command shows what packages are currently installed in a
 profile. For each installed package, it shows the following
 information:
 
-* `Index`: An integer that can be used to unambiguously identify the
+* `Name`: A unique name used to unambiguously identify the
   package in invocations of `nix profile remove` and `nix profile
   upgrade`.
 
+* `Index`: An integer that can be used to unambiguously identify the
+  package in invocations of `nix profile remove` and `nix profile upgrade`.
+  (*Deprecated, will be removed in a future version in favor of `Name`.*)
+
 * `Flake attribute`: The flake output attribute path that provides the
   package (e.g. `packages.x86_64-linux.hello`).
 

src/nix/profile-remove.md

@@ -2,16 +2,17 @@ R""(
 
 # Examples
 
-* Remove a package by position:
+* Remove a package by name:
 
   ```console
-  # nix profile remove 3
+  # nix profile remove hello
   ```
 
-* Remove a package by attribute path:
+* Remove a package by index
+  *(deprecated, will be removed in a future version)*:
 
   ```console
-  # nix profile remove packages.x86_64-linux.hello
+  # nix profile remove 3
   ```
 
 * Remove all packages:

src/nix/profile-upgrade.md

@@ -9,18 +9,16 @@ R""(
   # nix profile upgrade '.*'
   ```
 
-* Upgrade a specific package:
+* Upgrade a specific package by name:
 
   ```console
-  # nix profile upgrade packages.x86_64-linux.hello
+  # nix profile upgrade hello
   ```
 
-* Upgrade a specific profile element by number:
+* Upgrade a specific package by index
+  *(deprecated, will be removed in a future version)*:
 
   ```console
-  # nix profile list
-  0 flake:nixpkgs#legacyPackages.x86_64-linux.spotify …
-
   # nix profile upgrade 0
   ```