nix flake list-inputs: Pretty-print the tree

src/libutil/util.hh

@@ -458,6 +458,13 @@ void ignoreException();
 #define ANSI_BLUE "\e[34;1m"
 
 
+/* Tree formatting. */
+constexpr char treeConn[] = "╠═══";
+constexpr char treeLast[] = "╚═══";
+constexpr char treeLine[] = "║   ";
+constexpr char treeNull[] = "    ";
+
+
 /* Truncate a string to 'width' printable characters. If 'filterAll'
    is true, all ANSI escape sequences are filtered out. Otherwise,
    some escape sequences (such as colour setting) are copied but not
@@ -583,4 +590,31 @@ extern PathFilter defaultPathFilter;
 AutoCloseFD createUnixDomainSocket(const Path & path, mode_t mode);
 
 
+// A Rust/Python-like enumerate() iterator adapter.
+// Borrowed from http://reedbeta.com/blog/python-like-enumerate-in-cpp17.
+template <typename T,
+          typename TIter = decltype(std::begin(std::declval<T>())),
+          typename = decltype(std::end(std::declval<T>()))>
+constexpr auto enumerate(T && iterable)
+{
+    struct iterator
+    {
+        size_t i;
+        TIter iter;
+        bool operator != (const iterator & other) const { return iter != other.iter; }
+        void operator ++ () { ++i; ++iter; }
+        auto operator * () const { return std::tie(i, *iter); }
+    };
+
+    struct iterable_wrapper
+    {
+        T iterable;
+        auto begin() { return iterator{ 0, std::begin(iterable) }; }
+        auto end() { return iterator{ 0, std::end(iterable) }; }
+    };
+
+    return iterable_wrapper{ std::forward<T>(iterable) };
+}
+
+
 }

src/nix-store/nix-store.cc

@@ -229,12 +229,6 @@ static StorePathSet maybeUseOutputs(const StorePath & storePath, bool useOutput,
 /* Some code to print a tree representation of a derivation dependency
    graph.  Topological sorting is used to keep the tree relatively
    flat. */
-
-const string treeConn = "+---";
-const string treeLine = "|   ";
-const string treeNull = "    ";
-
-
 static void printTree(const StorePath & path,
     const string & firstPad, const string & tailPad, StorePathSet & done)
 {
@@ -254,10 +248,11 @@ static void printTree(const StorePath & path,
     auto sorted = store->topoSortPaths(info->references);
     reverse(sorted.begin(), sorted.end());
 
-    for (auto i = sorted.begin(); i != sorted.end(); ++i) {
+    for (const auto &[n, i] : enumerate(sorted)) {
-        auto j = i; ++j;
+        bool last = n + 1 == sorted.size();
-        printTree(*i, tailPad + treeConn,
+        printTree(i,
-            j == sorted.end() ? tailPad + treeNull : tailPad + treeLine,
+            tailPad + (last ? treeLast : treeConn),
+            tailPad + (last ? treeNull : treeLine),
             done);
     }
 }

src/nix/flake.cc

@@ -193,22 +193,27 @@ struct CmdFlakeListInputs : FlakeCommand, MixJSON
     {
         auto flake = lockFlake();
 
+        stopProgressBar();
+
         if (json)
             std::cout << ((LockedInputs &) flake.lockFile).toJson() << "\n";
         else {
             std::cout << fmt("%s\n", flake.flake.resolvedRef);
 
-            std::function<void(const LockedInputs & inputs, size_t depth)> recurse;
+            std::function<void(const LockedInputs & inputs, const std::string & prefix)> recurse;
 
-            recurse = [&](const LockedInputs & inputs, size_t depth)
+            recurse = [&](const LockedInputs & inputs, const std::string & prefix)
             {
-                for (auto & input : inputs.inputs) {
+                for (const auto & [i, input] : enumerate(inputs.inputs)) {
-                    std::cout << fmt("%s%s: %s\n", std::string(depth * 2, ' '), input.first, input.second.ref);
+                    //auto tree2 = tree.child(i + 1 == inputs.inputs.size());
-                    recurse(input.second, depth + 1);
+                    bool last = i + 1 == inputs.inputs.size();
+                    std::cout << fmt("%s" ANSI_BOLD "%s" ANSI_NORMAL ": %s\n",
+                        prefix + (last ? treeLast : treeConn), input.first, input.second.ref);
+                    recurse(input.second, prefix + (last ? treeNull : treeLine));
                 }
             };
 
-            recurse(flake.lockFile, 1);
+            recurse(flake.lockFile, "");
         }
     }
 };

src/nix/why-depends.cc

@@ -143,11 +143,6 @@ struct CmdWhyDepends : SourceExprCommand
            and `dependency`. */
         std::function<void(Node &, const string &, const string &)> printNode;
 
-        const string treeConn = "╠═══";
-        const string treeLast = "╚═══";
-        const string treeLine = "║   ";
-        const string treeNull = "    ";
-
         struct BailOut { };
 
         printNode = [&](Node & node, const string & firstPad, const string & tailPad) {

tests/dependencies.sh

@@ -6,7 +6,7 @@ drvPath=$(nix-instantiate dependencies.nix)
 
 echo "derivation is $drvPath"
 
-nix-store -q --tree "$drvPath" | grep '   +---.*builder1.sh'
+nix-store -q --tree "$drvPath" | grep '║   ╚═══.*builder1.sh'
 
 # Test Graphviz graph generation.
 nix-store -q --graph "$drvPath" > $TEST_ROOT/graph
@@ -24,7 +24,7 @@ if test -n "$dot"; then
     $dot < $TEST_ROOT/graph
 fi
 
-nix-store -q --tree "$outPath" | grep '+---.*dependencies-input-2'
+nix-store -q --tree "$outPath" | grep '═══.*dependencies-input-2'
 
 echo "output path is $outPath"