From af373c2ece2c14ac652313a6f370dc344c85f86e Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <edolstra@gmail.com>
Date: Thu, 3 Dec 2020 22:45:44 +0100
Subject: [PATCH] Add deprecated aliases for renamed commands

---
 src/libutil/args.cc |  5 +----
 src/libutil/args.hh |  5 +++--
 src/nix/main.cc     | 30 +++++++++++++++++++++++++++++-
 3 files changed, 33 insertions(+), 7 deletions(-)

diff --git a/src/libutil/args.cc b/src/libutil/args.cc
index 8bd9c8aeb..61f9503ec 100644
--- a/src/libutil/args.cc
+++ b/src/libutil/args.cc
@@ -86,6 +86,7 @@ void Args::parseCmdline(const Strings & _cmdline)
                 throw UsageError("unrecognised flag '%1%'", arg);
         }
         else {
+            pos = rewriteArgs(cmdline, pos);
             pendingArgs.push_back(*pos++);
             if (processArgs(pendingArgs, false))
                 pendingArgs.clear();
@@ -390,10 +391,6 @@ MultiCommand::MultiCommand(const Commands & commands)
         .optional = true,
         .handler = {[=](std::string s) {
             assert(!command);
-            if (auto alias = get(deprecatedAliases, s)) {
-                warn("'%s' is a deprecated alias for '%s'", s, *alias);
-                s = *alias;
-            }
             if (auto prefix = needsCompletion(s)) {
                 for (auto & [name, command] : commands)
                     if (hasPrefix(name, *prefix))
diff --git a/src/libutil/args.hh b/src/libutil/args.hh
index 26f1bc11b..8069fd70f 100644
--- a/src/libutil/args.hh
+++ b/src/libutil/args.hh
@@ -115,6 +115,9 @@ protected:
 
     virtual bool processArgs(const Strings & args, bool finish);
 
+    virtual Strings::iterator rewriteArgs(Strings & args, Strings::iterator pos)
+    { return pos; }
+
     std::set<std::string> hiddenCategories;
 
 public:
@@ -257,8 +260,6 @@ public:
 
     std::map<Command::Category, std::string> categories;
 
-    std::map<std::string, std::string> deprecatedAliases;
-
     // Selected command, if any.
     std::optional<std::pair<std::string, ref<Command>>> command;
 
diff --git a/src/nix/main.cc b/src/nix/main.cc
index 6d8c66406..94f4cad3c 100644
--- a/src/nix/main.cc
+++ b/src/nix/main.cc
@@ -112,8 +112,36 @@ struct NixArgs : virtual MultiCommand, virtual MixCommonArgs
             .description = "consider all previously downloaded files out-of-date",
             .handler = {[&]() { refresh = true; }},
         });
+    }
 
-        deprecatedAliases.insert({"dev-shell", "develop"});
+    std::map<std::string, std::vector<std::string>> aliases = {
+        {"dev-shell", {"develop"}},
+        {"hash-file", {"hash", "file"}},
+        {"hash-path", {"hash", "path"}},
+        {"to-base16", {"hash", "to-base16"}},
+        {"to-base32", {"hash", "to-base32"}},
+        {"to-base64", {"hash", "to-base64"}},
+        {"ls-nar", {"nar", "ls"}},
+        {"ls-store", {"store", "ls"}},
+        {"cat-nar", {"nar", "cat"}},
+        {"cat-store", {"store", "cat"}},
+    };
+
+    bool aliasUsed = false;
+
+    Strings::iterator rewriteArgs(Strings & args, Strings::iterator pos) override
+    {
+        if (aliasUsed || command || pos == args.end()) return pos;
+        auto arg = *pos;
+        auto i = aliases.find(arg);
+        if (i == aliases.end()) return pos;
+        warn("'%s' is a deprecated alias for '%s'",
+            arg, concatStringsSep(" ", i->second));
+        pos = args.erase(pos);
+        for (auto j = i->second.rbegin(); j != i->second.rend(); ++j)
+            pos = args.insert(pos, *j);
+        aliasUsed = true;
+        return pos;
     }
 
     void printFlags(std::ostream & out) override