From 4e477356fd8b9635ed82dfc67473ebcfd1d25ed8 Mon Sep 17 00:00:00 2001
From: AntoinePrv <AntoinePrv@users.noreply.github.com>
Date: Fri, 22 Dec 2023 10:50:50 +0100
Subject: [PATCH 1/3] Add flat_bool_expr_tree:infix_for_each

---
 .../include/mamba/util/flat_binary_tree.hpp   | 26 +++++
 .../mamba/util/flat_bool_expr_tree.hpp        | 98 ++++++++++++++++++-
 .../src/util/test_flat_bool_expr_tree.cpp     | 58 ++++++++++-
 3 files changed, 179 insertions(+), 3 deletions(-)

diff --git a/libmamba/include/mamba/util/flat_binary_tree.hpp b/libmamba/include/mamba/util/flat_binary_tree.hpp
index 85cd1b1f49..f7d1fd38eb 100644
--- a/libmamba/include/mamba/util/flat_binary_tree.hpp
+++ b/libmamba/include/mamba/util/flat_binary_tree.hpp
@@ -90,6 +90,9 @@ namespace mamba::util
         [[nodiscard]] auto right(idx_type idx) const -> idx_type;
         [[nodiscard]] auto root() const -> idx_type;
 
+        template <typename Visitor>
+        void dfs_raw(Visitor&& visitor, idx_type start) const;
+
     private:
 
         node_list m_nodes;
@@ -245,5 +248,28 @@ namespace mamba::util
     {
         return add_branch_impl(std::move(branch), left_child, right_child);
     }
+
+    template <typename B, typename L>
+    template <typename Visitor>
+    void flat_binary_tree<B, L>::dfs_raw(Visitor&& visitor, idx_type start_idx) const
+    {
+        if (is_leaf(start_idx))
+        {
+            visitor.on_leaf(*this, start_idx);
+        }
+        else
+        {
+            const auto left_idx = left(start_idx);
+            const auto right_idx = right(start_idx);
+
+            visitor.on_branch_left_before(*this, start_idx, left_idx);
+            dfs_raw(visitor, left_idx);
+
+            visitor.on_branch_infix(*this, start_idx, left_idx, right_idx);
+
+            dfs_raw(visitor, right_idx);
+            visitor.on_branch_right_after(*this, start_idx, right_idx);
+        }
+    }
 }
 #endif
diff --git a/libmamba/include/mamba/util/flat_bool_expr_tree.hpp b/libmamba/include/mamba/util/flat_bool_expr_tree.hpp
index 29db94969f..96fe07579e 100644
--- a/libmamba/include/mamba/util/flat_bool_expr_tree.hpp
+++ b/libmamba/include/mamba/util/flat_bool_expr_tree.hpp
@@ -9,9 +9,7 @@
 
 #include <cassert>
 #include <functional>
-#include <iterator>
 #include <stdexcept>
-#include <type_traits>
 #include <utility>
 #include <variant>
 #include <vector>
@@ -150,6 +148,14 @@ namespace mamba::util
         using tree_type = flat_binary_tree<operator_type, variable_type>;
         using size_type = typename tree_type::size_type;
 
+        struct LeftParenthesis
+        {
+        };
+
+        struct RightParenthesis
+        {
+        };
+
         flat_bool_expr_tree() = default;
         flat_bool_expr_tree(const flat_bool_expr_tree&) = default;
         flat_bool_expr_tree(flat_bool_expr_tree&&) = default;
@@ -169,6 +175,9 @@ namespace mamba::util
         [[nodiscard]] auto evaluate(UnaryFunc&& var_evaluator = {}, bool empty_val = true) const
             -> bool;
 
+        template <typename UnaryFunc>
+        void infix_for_each(UnaryFunc&& func) const;
+
     private:
 
         using idx_type = typename tree_type::idx_type;
@@ -179,6 +188,42 @@ namespace mamba::util
         tree_type m_tree = {};
     };
 
+    template <typename V>
+    constexpr auto operator==(
+        typename flat_bool_expr_tree<V>::LeftParenthesis,
+        typename flat_bool_expr_tree<V>::LeftParenthesis
+    ) -> bool
+    {
+        return true;
+    }
+
+    template <typename V>
+    constexpr auto operator!=(
+        typename flat_bool_expr_tree<V>::LeftParenthesis,
+        typename flat_bool_expr_tree<V>::LeftParenthesis
+    ) -> bool
+    {
+        return false;
+    }
+
+    template <typename V>
+    constexpr auto operator==(
+        typename flat_bool_expr_tree<V>::RightParenthesis,
+        typename flat_bool_expr_tree<V>::RightParenthesis
+    ) -> bool
+    {
+        return true;
+    }
+
+    template <typename V>
+    constexpr auto operator!=(
+        typename flat_bool_expr_tree<V>::RightParenthesis,
+        typename flat_bool_expr_tree<V>::RightParenthesis
+    ) -> bool
+    {
+        return false;
+    }
+
     /*************************************
      *  Implementation of PostfixParser  *
      *************************************/
@@ -551,5 +596,54 @@ namespace mamba::util
                    || evaluate_impl(var_eval, m_tree.right(idx));
         }
     }
+
+    template <typename V>
+    template <typename UnaryFunc>
+    void flat_bool_expr_tree<V>::infix_for_each(UnaryFunc&& func) const
+    {
+        struct TreeVisitor
+        {
+            using idx_type = typename tree_type::idx_type;
+
+            void on_leaf(const tree_type& tree, idx_type idx)
+            {
+                m_func(tree.leaf(idx));
+            }
+
+            void on_branch_left_before(const tree_type& tree, idx_type, idx_type left_idx)
+            {
+                if (!tree.is_leaf(left_idx))
+                {
+                    m_func(LeftParenthesis{});
+                }
+            }
+
+            void
+            on_branch_infix(const tree_type& tree, idx_type branch_idx, idx_type left_idx, idx_type right_idx)
+            {
+                if (!tree.is_leaf(left_idx))
+                {
+                    m_func(RightParenthesis{});
+                }
+                m_func(tree.branch(branch_idx));
+                if (!tree.is_leaf(right_idx))
+                {
+                    m_func(LeftParenthesis{});
+                }
+            }
+
+            void on_branch_right_after(const tree_type& tree, idx_type, idx_type right_idx)
+            {
+                if (!tree.is_leaf(right_idx))
+                {
+                    m_func(RightParenthesis{});
+                }
+            }
+
+            UnaryFunc m_func;
+        } tree_visitor{ std::forward<UnaryFunc>(func) };
+
+        m_tree.dfs_raw(tree_visitor, m_tree.root());
+    }
 }
 #endif
diff --git a/libmamba/tests/src/util/test_flat_bool_expr_tree.cpp b/libmamba/tests/src/util/test_flat_bool_expr_tree.cpp
index b1a99d9e22..11e4c8f827 100644
--- a/libmamba/tests/src/util/test_flat_bool_expr_tree.cpp
+++ b/libmamba/tests/src/util/test_flat_bool_expr_tree.cpp
@@ -8,7 +8,6 @@
 #include <array>
 #include <stdexcept>
 #include <string>
-#include <variant>
 #include <vector>
 
 #include <doctest/doctest.h>
@@ -466,6 +465,7 @@ TEST_SUITE("util::flat_bool_expr_tree")
     {
         const auto reference_eval = [](std::array<bool, 5> x) -> bool
         { return (x[0] || x[1]) && (x[2] && (x[3] || x[4])); };
+        // Infix:     ((x3 or x4) and x2) and (x0 or x1)
         // Postfix:   x0 x1 or x2 x3 x4 or and and
         auto parser = PostfixParser<std::size_t, BoolOperator>{};
         parser.push_variable(0);
@@ -493,6 +493,7 @@ TEST_SUITE("util::flat_bool_expr_tree")
         const auto reference_eval = [](std::array<bool, 7> x) -> bool
         { return ((x[0] || x[1]) && (x[2] || x[3] || x[4]) && x[5]) || x[6]; };
         auto parser = InfixParser<std::size_t, BoolOperator>{};
+        // Infix:  ((x0 or x1) and (x2 or x3 or x4) and x5) or x6
         parser.push_left_parenthesis();
         parser.push_left_parenthesis();
         parser.push_variable(0);
@@ -524,4 +525,59 @@ TEST_SUITE("util::flat_bool_expr_tree")
             CHECK_EQ(tree.evaluate(eval), reference_eval(values));
         }
     }
+
+    TEST_CASE("Infix traversal")
+    {
+        auto parser = InfixParser<std::size_t, BoolOperator>{};
+        // Infix:  ((x0 or x1) and (x2 or x3 or x4) and x5) or x6
+        parser.push_left_parenthesis();
+        parser.push_left_parenthesis();
+        parser.push_variable(0);
+        parser.push_operator(BoolOperator::logical_or);
+        parser.push_variable(1);
+        parser.push_right_parenthesis();
+        parser.push_operator(BoolOperator::logical_and);
+        parser.push_left_parenthesis();
+        parser.push_variable(2);
+        parser.push_operator(BoolOperator::logical_or);
+        parser.push_variable(3);
+        parser.push_operator(BoolOperator::logical_or);
+        parser.push_variable(4);
+        parser.push_right_parenthesis();
+        parser.push_operator(BoolOperator::logical_and);
+        parser.push_variable(5);
+        parser.push_right_parenthesis();
+        parser.push_operator(BoolOperator::logical_or);
+        parser.push_variable(6);
+        parser.finalize();
+        auto tree = flat_bool_expr_tree(std::move(parser).tree());
+
+        auto result = std::string();
+        tree.infix_for_each(
+            [&](const auto& token)
+            {
+                using tree_type = decltype(tree);
+                using Token = std::decay_t<decltype(token)>;
+                if constexpr (std::is_same_v<Token, tree_type::LeftParenthesis>)
+                {
+                    result += '(';
+                }
+                if constexpr (std::is_same_v<Token, tree_type::RightParenthesis>)
+                {
+                    result += ')';
+                }
+                if constexpr (std::is_same_v<Token, BoolOperator>)
+                {
+                    result += (token == BoolOperator::logical_or) ? " or " : " and ";
+                }
+                if constexpr (std::is_same_v<Token, tree_type::variable_type>)
+                {
+                    result += 'x';
+                    result += std::to_string(token);
+                }
+            }
+        );
+        // There could be many representations, here is one
+        CHECK_EQ(result, "((x0 or x1) and ((x2 or (x3 or x4)) and x5)) or x6");
+    }
 }

From cd4af890bc20d2cb954d9cac7c5577889a038c7e Mon Sep 17 00:00:00 2001
From: AntoinePrv <AntoinePrv@users.noreply.github.com>
Date: Fri, 22 Dec 2023 12:20:13 +0100
Subject: [PATCH 2/3] Add level to Version repr

---
 libmamba/include/mamba/specs/version.hpp     | 84 +++++------------
 libmamba/src/specs/version.cpp               | 95 ++++++++++++++++++++
 libmamba/tests/src/specs/test_version.cpp    | 47 +++++++---
 libmambapy/src/libmambapy/bindings/specs.cpp |  8 +-
 libmambapy/tests/test_specs.py               |  1 +
 5 files changed, 160 insertions(+), 75 deletions(-)

diff --git a/libmamba/include/mamba/specs/version.hpp b/libmamba/include/mamba/specs/version.hpp
index 358e1b3ccc..d19d3765ae 100644
--- a/libmamba/include/mamba/specs/version.hpp
+++ b/libmamba/include/mamba/specs/version.hpp
@@ -7,6 +7,7 @@
 #ifndef MAMBA_SPECS_VERSION_HPP
 #define MAMBA_SPECS_VERSION_HPP
 
+#include <optional>
 #include <string>
 #include <string_view>
 #include <vector>
@@ -110,8 +111,24 @@ namespace mamba::specs
         [[nodiscard]] auto version() const noexcept -> const CommonVersion&;
         [[nodiscard]] auto local() const noexcept -> const CommonVersion&;
 
+        /**
+         * A string representation of the version.
+         *
+         * May not always be the same as the parsed string (due to reconstruction) but reparsing
+         * this string will give the same version.
+         * ``v == Version::parse(v.str())``.
+         */
         [[nodiscard]] auto str() const -> std::string;
 
+        /**
+         * A string truncated of extended representation of the version.
+         *
+         * Represent the string with the desired number of parts.
+         * If the actual number of parts is larger, then the string is truncated.
+         * If the actual number of parts is smalle, then the string is expanded with zeros.
+         */
+        [[nodiscard]] auto str(std::size_t level) const -> std::string;
+
         [[nodiscard]] auto operator==(const Version& other) const -> bool;
         [[nodiscard]] auto operator!=(const Version& other) const -> bool;
         [[nodiscard]] auto operator<(const Version& other) const -> bool;
@@ -156,73 +173,20 @@ namespace mamba::specs
 template <>
 struct fmt::formatter<mamba::specs::VersionPartAtom>
 {
-    constexpr auto parse(format_parse_context& ctx) -> decltype(ctx.begin())
-    {
-        // make sure that range is empty
-        if (ctx.begin() != ctx.end() && *ctx.begin() != '}')
-        {
-            throw fmt::format_error("Invalid format");
-        }
-        return ctx.begin();
-    }
+    auto parse(format_parse_context& ctx) -> decltype(ctx.begin());
 
-    template <class FormatContext>
-    auto format(const ::mamba::specs::VersionPartAtom atom, FormatContext& ctx)
-    {
-        return fmt::format_to(ctx.out(), "{}{}", atom.numeral(), atom.literal());
-    }
+    auto format(const ::mamba::specs::VersionPartAtom atom, format_context& ctx)
+        -> decltype(ctx.out());
 };
 
 template <>
 struct fmt::formatter<mamba::specs::Version>
 {
-    constexpr auto parse(format_parse_context& ctx) -> decltype(ctx.begin())
-    {
-        // make sure that range is empty
-        if (ctx.begin() != ctx.end() && *ctx.begin() != '}')
-        {
-            throw fmt::format_error("Invalid format");
-        }
-        return ctx.begin();
-    }
+    std::optional<std::size_t> m_level;
 
-    template <class FormatContext>
-    auto format(const ::mamba::specs::Version v, FormatContext& ctx)
-    {
-        auto out = ctx.out();
-        if (v.epoch() != 0)
-        {
-            out = fmt::format_to(ctx.out(), "{}!", v.epoch());
-        }
-
-        auto format_version_to = [](auto l_out, const auto& version)
-        {
-            bool first = true;
-            for (const auto& part : version)
-            {
-                if (first)
-                {
-                    first = false;
-                }
-                else
-                {
-                    l_out = fmt::format_to(l_out, ".");
-                }
-                for (const auto& atom : part)
-                {
-                    l_out = fmt::format_to(l_out, "{}", atom);
-                }
-            }
-            return l_out;
-        };
-        out = format_version_to(out, v.version());
-        if (!v.local().empty())
-        {
-            out = fmt::format_to(out, "+");
-            out = format_version_to(out, v.local());
-        }
-        return out;
-    }
+    auto parse(format_parse_context& ctx) -> decltype(ctx.begin());
+
+    auto format(const ::mamba::specs::Version v, format_context& ctx) -> decltype(ctx.out());
 };
 
 #endif
diff --git a/libmamba/src/specs/version.cpp b/libmamba/src/specs/version.cpp
index 6221fcfe9a..6578cfd405 100644
--- a/libmamba/src/specs/version.cpp
+++ b/libmamba/src/specs/version.cpp
@@ -174,6 +174,31 @@ namespace mamba::specs
     {
         return compare_three_way(*this, other) != strong_ordering::less;
     }
+}
+
+auto
+fmt::formatter<mamba::specs::VersionPartAtom>::parse(format_parse_context& ctx)
+    -> decltype(ctx.begin())
+{
+    // make sure that range is empty
+    if (ctx.begin() != ctx.end() && *ctx.begin() != '}')
+    {
+        throw fmt::format_error("Invalid format");
+    }
+    return ctx.begin();
+}
+
+auto
+fmt::formatter<mamba::specs::VersionPartAtom>::format(
+    const ::mamba::specs::VersionPartAtom atom,
+    format_context& ctx
+) -> decltype(ctx.out())
+{
+    return fmt::format_to(ctx.out(), "{}{}", atom.numeral(), atom.literal());
+}
+
+namespace mamba::specs
+{
 
     /*******************************
      *  Implementation of Version  *
@@ -206,6 +231,15 @@ namespace mamba::specs
         return fmt::format("{}", *this);
     }
 
+    auto Version::str(std::size_t level) const -> std::string
+    {
+        // We should be able to do, as it works with numbers but it is not clear how this works
+        // with the cusotm parser
+        // return fmt::format("{:{}}", *this, level);
+        auto fmt = fmt::format("{{:{}}}", level);
+        return fmt::format(fmt, *this);
+    }
+
     namespace
     {
         /**
@@ -713,3 +747,64 @@ namespace mamba::specs
         }
     }
 }
+
+auto
+fmt::formatter<mamba::specs::Version>::parse(format_parse_context& ctx) -> decltype(ctx.begin())
+{
+    // make sure that range is not empty
+    if (ctx.begin() == ctx.end() || *ctx.begin() == '}')
+    {
+        return ctx.begin();
+    }
+    std::size_t val = 0;
+    auto [ptr, ec] = std::from_chars(ctx.begin(), ctx.end(), val);
+    if (ec != std::errc())
+    {
+        throw fmt::format_error("Invalid format" + std::string(ctx.begin(), ctx.end()));
+    }
+    m_level = val;
+    return ptr;
+}
+
+auto
+fmt::formatter<mamba::specs::Version>::format(const ::mamba::specs::Version v, format_context& ctx)
+    -> decltype(ctx.out())
+{
+    auto out = ctx.out();
+    if (v.epoch() != 0)
+    {
+        out = fmt::format_to(ctx.out(), "{}!", v.epoch());
+    }
+
+
+    auto format_version_to = [this](auto l_out, const auto& version)
+    {
+        auto const n_levels = m_level.value_or(version.size());
+        for (std::size_t i = 0; i < n_levels; ++i)
+        {
+            if (i != 0)
+            {
+                l_out = fmt::format_to(l_out, ".");
+            }
+            if (i < version.size())
+            {
+                for (const auto& atom : version[i])
+                {
+                    l_out = fmt::format_to(l_out, "{}", atom);
+                }
+            }
+            else
+            {
+                l_out = fmt::format_to(l_out, "0");
+            }
+        }
+        return l_out;
+    };
+    out = format_version_to(out, v.version());
+    if (!v.local().empty())
+    {
+        out = fmt::format_to(out, "+");
+        out = format_version_to(out, v.local());
+    }
+    return out;
+}
diff --git a/libmamba/tests/src/specs/test_version.cpp b/libmamba/tests/src/specs/test_version.cpp
index f42d956886..752fa952d6 100644
--- a/libmamba/tests/src/specs/test_version.cpp
+++ b/libmamba/tests/src/specs/test_version.cpp
@@ -6,7 +6,6 @@
 
 #include <algorithm>
 #include <array>
-#include <string>
 #include <vector>
 
 #include <doctest/doctest.h>
@@ -306,20 +305,40 @@ TEST_SUITE("specs::version")
 
     TEST_CASE("version_format")
     {
-        // clang-format off
-            CHECK_EQ(
-                Version(0, {{{11, "a"}, {0, "post"}}, {{3}}, {{4, "dev"}}}).str(),
-                "11a0post.3.4dev"
-            );
-            CHECK_EQ(
-                Version(1, {{{11, "a"}, {0}}, {{3}}, {{4, "dev"}}}).str(),
-                "1!11a0.3.4dev"
-            );
-            CHECK_EQ(
-                Version(1, {{{11, "a"}, {0}}, {{3}}, {{4, "dev"}}}, {{{1}}, {{2}}}).str(),
-                "1!11a0.3.4dev+1.2"
+        SUBCASE("11a0post.3.4dev")
+        {
+            auto v = Version(0, { { { 11, "a" }, { 0, "post" } }, { { 3 } }, { { 4, "dev" } } });
+            CHECK_EQ(v.str(), "11a0post.3.4dev");
+            CHECK_EQ(v.str(1), "11a0post");
+            CHECK_EQ(v.str(2), "11a0post.3");
+            CHECK_EQ(v.str(3), "11a0post.3.4dev");
+            CHECK_EQ(v.str(4), "11a0post.3.4dev.0");
+            CHECK_EQ(v.str(5), "11a0post.3.4dev.0.0");
+        }
+
+        SUBCASE("1!11a0.3.4dev")
+        {
+            auto v = Version(1, { { { 11, "a" }, { 0 } }, { { 3 } }, { { 4, "dev" } } });
+            CHECK_EQ(v.str(), "1!11a0.3.4dev");
+            CHECK_EQ(v.str(1), "1!11a0");
+            CHECK_EQ(v.str(2), "1!11a0.3");
+            CHECK_EQ(v.str(3), "1!11a0.3.4dev");
+            CHECK_EQ(v.str(4), "1!11a0.3.4dev.0");
+        }
+
+        SUBCASE("1!11a0.3.4dev+1.2")
+        {
+            auto v = Version(
+                1,
+                { { { 11, "a" }, { 0 } }, { { 3 } }, { { 4, "dev" } } },
+                { { { 1 } }, { { 2 } } }
             );
-        // clang-format on
+            CHECK_EQ(v.str(), "1!11a0.3.4dev+1.2");
+            CHECK_EQ(v.str(1), "1!11a0+1");
+            CHECK_EQ(v.str(2), "1!11a0.3+1.2");
+            CHECK_EQ(v.str(3), "1!11a0.3.4dev+1.2.0");
+            CHECK_EQ(v.str(4), "1!11a0.3.4dev.0+1.2.0.0");
+        }
     }
 
     /**
diff --git a/libmambapy/src/libmambapy/bindings/specs.cpp b/libmambapy/src/libmambapy/bindings/specs.cpp
index 7336dfe8f5..681f361869 100644
--- a/libmambapy/src/libmambapy/bindings/specs.cpp
+++ b/libmambapy/src/libmambapy/bindings/specs.cpp
@@ -525,7 +525,13 @@ namespace mambapy
             .def_property_readonly("local", &Version::local)
             .def("starts_with", &Version::starts_with, py::arg("prefix"))
             .def("compatible_with", &Version::compatible_with, py::arg("older"), py::arg("level"))
-            .def("__str__", &Version::str)
+            .def("__str__", [](const Version& v) { return v.str(); })
+            .def("str", [](const Version& v) { return v.str(); })
+            .def(
+                "str",
+                [](const Version& v, std::size_t level) { return v.str(level); },
+                py::arg("level")
+            )
             .def(py::self == py::self)
             .def(py::self != py::self)
             .def(py::self < py::self)
diff --git a/libmambapy/tests/test_specs.py b/libmambapy/tests/test_specs.py
index 6af55330ef..cefaa327e3 100644
--- a/libmambapy/tests/test_specs.py
+++ b/libmambapy/tests/test_specs.py
@@ -604,6 +604,7 @@ def test_Version():
 
     # str
     assert str(v) == "3!1.3ab2.4+42.0alpha"
+    assert v.str(level=1) == "3!1+42"
 
     # Copy
     assert copy.deepcopy(v) == v

From 49a71377787a7cb11a56207b43a722916c9ba4d7 Mon Sep 17 00:00:00 2001
From: AntoinePrv <AntoinePrv@users.noreply.github.com>
Date: Fri, 22 Dec 2023 13:10:09 +0100
Subject: [PATCH 3/3] Add VersionSpec::str

---
 libmamba/include/mamba/specs/version_spec.hpp |  50 ++++++
 libmamba/src/specs/version_spec.cpp           | 170 +++++++++++++++++-
 .../tests/src/specs/test_version_spec.cpp     |  15 ++
 libmambapy/src/libmambapy/bindings/specs.cpp  |   1 +
 libmambapy/tests/test_specs.py                |   7 +-
 5 files changed, 233 insertions(+), 10 deletions(-)

diff --git a/libmamba/include/mamba/specs/version_spec.hpp b/libmamba/include/mamba/specs/version_spec.hpp
index 1a08293de6..e0d8bd325e 100644
--- a/libmamba/include/mamba/specs/version_spec.hpp
+++ b/libmamba/include/mamba/specs/version_spec.hpp
@@ -11,11 +11,16 @@
 #include <string_view>
 #include <variant>
 
+#include <fmt/format.h>
+
 #include "mamba/specs/version.hpp"
 #include "mamba/util/flat_bool_expr_tree.hpp"
 
 namespace mamba::specs
 {
+    /**
+     * A stateful unary boolean function on the Version space.
+     */
     class VersionPredicate
     {
     public:
@@ -35,8 +40,13 @@ namespace mamba::specs
         /** Construct an free interval. */
         VersionPredicate() = default;
 
+        /**
+         * True if the predicate contains the given version.
+         */
         [[nodiscard]] auto contains(const Version& point) const -> bool;
 
+        [[nodiscard]] auto str() const -> std::string;
+
     private:
 
         struct free_interval
@@ -90,11 +100,23 @@ namespace mamba::specs
         friend auto operator==(not_starts_with, not_starts_with) -> bool;
         friend auto operator==(compatible_with, compatible_with) -> bool;
         friend auto operator==(const VersionPredicate& lhs, const VersionPredicate& rhs) -> bool;
+        friend class ::fmt::formatter<VersionPredicate>;
     };
 
     auto operator==(const VersionPredicate& lhs, const VersionPredicate& rhs) -> bool;
     auto operator!=(const VersionPredicate& lhs, const VersionPredicate& rhs) -> bool;
 
+    /**
+     * Represent a set of versions.
+     *
+     * Internally, a VersionSpec is a binary expression tree of union (or) or intersections (and)
+     * of the sets represented by VersionPredicate.
+     *
+     * The VersionSpec can itself be considered a complex predicate on the space of Version.
+     *
+     * Due to the complex nature of the expression system (comutativity, associativity, etc.), there
+     * is no easy way to say if two VersionSpecs are equal.
+     */
     class VersionSpec
     {
     public:
@@ -123,12 +145,24 @@ namespace mamba::specs
         VersionSpec() = default;
         explicit VersionSpec(tree_type&& tree) noexcept;
 
+        /**
+         * A string representation of the version spec.
+         *
+         * May not always be the same as the parsed string (due to reconstruction) but reparsing
+         * this string will give the same version spec.
+         */
         [[nodiscard]] auto str() const -> std::string;
+
+        /**
+         * True if the set described by the VersionSpec contains the given version.
+         */
         [[nodiscard]] auto contains(const Version& point) const -> bool;
 
     private:
 
         tree_type m_tree;
+
+        friend class ::fmt::formatter<VersionSpec>;
     };
 
     namespace version_spec_literals
@@ -137,4 +171,20 @@ namespace mamba::specs
     }
 }
 
+template <>
+struct fmt::formatter<mamba::specs::VersionPredicate>
+{
+    auto parse(format_parse_context& ctx) -> decltype(ctx.begin());
+
+    auto format(const ::mamba::specs::VersionPredicate& pred, format_context& ctx)
+        -> decltype(ctx.out());
+};
+
+template <>
+struct fmt::formatter<mamba::specs::VersionSpec>
+{
+    auto parse(format_parse_context& ctx) -> decltype(ctx.begin());
+
+    auto format(const ::mamba::specs::VersionSpec& spec, format_context& ctx) -> decltype(ctx.out());
+};
 #endif
diff --git a/libmamba/src/specs/version_spec.cpp b/libmamba/src/specs/version_spec.cpp
index 8940a1b5b7..addd8d5b53 100644
--- a/libmamba/src/specs/version_spec.cpp
+++ b/libmamba/src/specs/version_spec.cpp
@@ -6,7 +6,6 @@
 
 #include <algorithm>
 #include <array>
-#include <cassert>
 #include <stdexcept>
 #include <type_traits>
 
@@ -156,6 +155,11 @@ namespace mamba::specs
         return VersionPredicate(std::move(ver), compatible_with{ level });
     }
 
+    auto VersionPredicate::str() const -> std::string
+    {
+        return fmt::format("{}", *this);
+    }
+
     VersionPredicate::VersionPredicate(Version ver, BinaryOperator op)
         : m_version(std::move(ver))
         , m_operator(std::move(op))
@@ -171,6 +175,99 @@ namespace mamba::specs
     {
         return !(lhs == rhs);
     }
+}
+
+auto
+fmt::formatter<mamba::specs::VersionPredicate>::parse(format_parse_context& ctx)
+    -> decltype(ctx.begin())
+{
+    // make sure that range is empty
+    if (ctx.begin() != ctx.end() && *ctx.begin() != '}')
+    {
+        throw fmt::format_error("Invalid format");
+    }
+    return ctx.begin();
+}
+
+auto
+fmt::formatter<mamba::specs::VersionPredicate>::format(
+    const ::mamba::specs::VersionPredicate& pred,
+    format_context& ctx
+) -> decltype(ctx.out())
+{
+    using VersionPredicate = typename mamba::specs::VersionPredicate;
+    using VersionSpec = typename mamba::specs::VersionSpec;
+    using Version = typename mamba::specs::Version;
+
+    auto out = ctx.out();
+    std::visit(
+        [&](const auto& op)
+        {
+            using Op = std::decay_t<decltype(op)>;
+            if constexpr (std::is_same_v<Op, VersionPredicate::free_interval>)
+            {
+                out = fmt::format_to(
+                    out,
+                    "{}{}",
+                    VersionSpec::starts_with_str,
+                    VersionSpec::glob_suffix_token
+                );
+            }
+            if constexpr (std::is_same_v<Op, std::equal_to<Version>>)
+            {
+                out = fmt::format_to(out, "{}{}", VersionSpec::equal_str, pred.m_version);
+            }
+            if constexpr (std::is_same_v<Op, std::not_equal_to<Version>>)
+            {
+                out = fmt::format_to(out, "{}{}", VersionSpec::not_equal_str, pred.m_version);
+            }
+            if constexpr (std::is_same_v<Op, std::greater<Version>>)
+            {
+                out = fmt::format_to(out, "{}{}", VersionSpec::greater_str, pred.m_version);
+            }
+            if constexpr (std::is_same_v<Op, std::greater_equal<Version>>)
+            {
+                out = fmt::format_to(out, "{}{}", VersionSpec::greater_equal_str, pred.m_version);
+            }
+            if constexpr (std::is_same_v<Op, std::less<Version>>)
+            {
+                out = fmt::format_to(out, "{}{}", VersionSpec::less_str, pred.m_version);
+            }
+            if constexpr (std::is_same_v<Op, std::less_equal<Version>>)
+            {
+                out = fmt::format_to(out, "{}{}", VersionSpec::less_equal_str, pred.m_version);
+            }
+            if constexpr (std::is_same_v<Op, VersionPredicate::starts_with>)
+            {
+                out = fmt::format_to(out, "{}{}", VersionSpec::starts_with_str, pred.m_version);
+            }
+            if constexpr (std::is_same_v<Op, VersionPredicate::not_starts_with>)
+            {
+                out = fmt::format_to(
+                    out,
+                    "{}{}{}",
+                    VersionSpec::not_equal_str,
+                    pred.m_version,
+                    VersionSpec::glob_suffix_str
+                );
+            }
+            if constexpr (std::is_same_v<Op, VersionPredicate::compatible_with>)
+            {
+                out = fmt::format_to(
+                    out,
+                    "{}{}",
+                    VersionSpec::compatible_str,
+                    pred.m_version.str(op.level)
+                );
+            }
+        },
+        pred.m_operator
+    );
+    return out;
+}
+
+namespace mamba::specs
+{
 
     /********************************
      *  VersionSpec Implementation  *
@@ -186,6 +283,11 @@ namespace mamba::specs
         return m_tree.evaluate([&point](const auto& node) { return node.contains(point); });
     }
 
+    auto VersionSpec::str() const -> std::string
+    {
+        return fmt::format("{}", *this);
+    }
+
     namespace
     {
         auto is_char(std::string_view str, char c) -> bool
@@ -229,15 +331,15 @@ namespace mamba::specs
             {
                 auto ver = Version::parse(str.substr(VersionSpec::compatible_str.size()));
                 // in ``~=1.1`` level is assumed to be 1, in ``~=1.1.1`` level 2, etc.
-                static std::size_t constexpr one = std::size_t(1);  // MSVC
+                static constexpr std::size_t one = std::size_t(1);  // MSVC
                 const std::size_t level = std::max(ver.version().size(), one) - one;
                 return VersionPredicate::make_compatible_with(std::move(ver), level);
             }
             const bool has_glob_suffix = util::ends_with(str, VersionSpec::glob_suffix_str);
-            std::size_t const glob_len = has_glob_suffix * VersionSpec::glob_suffix_str.size();
+            const std::size_t glob_len = has_glob_suffix * VersionSpec::glob_suffix_str.size();
             if (util::starts_with(str, VersionSpec::equal_str))
             {
-                std::size_t const start = VersionSpec::equal_str.size();
+                const std::size_t start = VersionSpec::equal_str.size();
                 // Glob suffix changes meaning for ==1.3.*
                 if (has_glob_suffix)
                 {
@@ -252,7 +354,7 @@ namespace mamba::specs
             }
             if (util::starts_with(str, VersionSpec::not_equal_str))
             {
-                std::size_t const start = VersionSpec::not_equal_str.size();
+                const std::size_t start = VersionSpec::not_equal_str.size();
                 // Glob suffix changes meaning for !=1.3.*
                 if (has_glob_suffix)
                 {
@@ -267,7 +369,7 @@ namespace mamba::specs
             }
             if (util::starts_with(str, VersionSpec::starts_with_str))
             {
-                std::size_t const start = VersionSpec::starts_with_str.size();
+                const std::size_t start = VersionSpec::starts_with_str.size();
                 // Glob suffix does not change meaning for =1.3.*
                 return VersionPredicate::make_starts_with(
                     Version::parse(str.substr(start, str.size() - glob_len - start))
@@ -279,8 +381,8 @@ namespace mamba::specs
                 if (util::ends_with(str, VersionSpec::glob_suffix_token))
                 {
                     // either ".*" or "*"
-                    static std::size_t constexpr one = std::size_t(1);  // MSVC
-                    std::size_t const len = str.size() - std::max(glob_len, one);
+                    static constexpr std::size_t one = std::size_t(1);  // MSVC
+                    const std::size_t len = str.size() - std::max(glob_len, one);
                     return VersionPredicate::make_starts_with(Version::parse(str.substr(0, len)));
                 }
                 else
@@ -348,3 +450,55 @@ namespace mamba::specs
         }
     }
 }
+
+auto
+fmt::formatter<mamba::specs::VersionSpec>::parse(format_parse_context& ctx) -> decltype(ctx.begin())
+{
+    // make sure that range is empty
+    if (ctx.begin() != ctx.end() && *ctx.begin() != '}')
+    {
+        throw fmt::format_error("Invalid format");
+    }
+    return ctx.begin();
+}
+
+auto
+fmt::formatter<mamba::specs::VersionSpec>::format(
+    const ::mamba::specs::VersionSpec& spec,
+    format_context& ctx
+) -> decltype(ctx.out())
+{
+    auto out = ctx.out();
+    spec.m_tree.infix_for_each(
+        [&](const auto& token)
+        {
+            using VersionSpec = typename mamba::specs::VersionSpec;
+            using tree_type = typename VersionSpec::tree_type;
+            using Token = std::decay_t<decltype(token)>;
+            if constexpr (std::is_same_v<Token, tree_type::LeftParenthesis>)
+            {
+                out = fmt::format_to(out, "{}", VersionSpec::left_parenthesis_token);
+            }
+            if constexpr (std::is_same_v<Token, tree_type::RightParenthesis>)
+            {
+                out = fmt::format_to(out, "{}", VersionSpec::right_parenthesis_token);
+            }
+            if constexpr (std::is_same_v<Token, tree_type::operator_type>)
+            {
+                if (token == tree_type::operator_type::logical_or)
+                {
+                    out = fmt::format_to(out, "{}", VersionSpec::or_token);
+                }
+                else
+                {
+                    out = fmt::format_to(out, "{}", VersionSpec::and_token);
+                }
+            }
+            if constexpr (std::is_same_v<Token, tree_type::variable_type>)
+            {
+                out = fmt::format_to(out, "{}", token);
+            }
+        }
+    );
+    return out;
+}
diff --git a/libmamba/tests/src/specs/test_version_spec.cpp b/libmamba/tests/src/specs/test_version_spec.cpp
index 9d4443f5ff..5e536a35cd 100644
--- a/libmamba/tests/src/specs/test_version_spec.cpp
+++ b/libmamba/tests/src/specs/test_version_spec.cpp
@@ -29,42 +29,49 @@ TEST_SUITE("specs::version_spec")
         CHECK(free.contains(v2));
         CHECK(free.contains(v3));
         CHECK(free.contains(v4));
+        CHECK_EQ(free.str(), "=*");
 
         const auto eq = VersionPredicate::make_equal_to(v2);
         CHECK_FALSE(eq.contains(v1));
         CHECK(eq.contains(v2));
         CHECK_FALSE(eq.contains(v3));
         CHECK_FALSE(eq.contains(v4));
+        CHECK_EQ(eq.str(), "==2.0");
 
         const auto ne = VersionPredicate::make_not_equal_to(v2);
         CHECK(ne.contains(v1));
         CHECK_FALSE(ne.contains(v2));
         CHECK(ne.contains(v3));
         CHECK(ne.contains(v4));
+        CHECK_EQ(ne.str(), "!=2.0");
 
         const auto gt = VersionPredicate::make_greater(v2);
         CHECK_FALSE(gt.contains(v1));
         CHECK_FALSE(gt.contains(v2));
         CHECK(gt.contains(v3));
         CHECK(gt.contains(v4));
+        CHECK_EQ(gt.str(), ">2.0");
 
         const auto ge = VersionPredicate::make_greater_equal(v2);
         CHECK_FALSE(ge.contains(v1));
         CHECK(ge.contains(v2));
         CHECK(ge.contains(v3));
         CHECK(ge.contains(v4));
+        CHECK_EQ(ge.str(), ">=2.0");
 
         const auto lt = VersionPredicate::make_less(v2);
         CHECK(lt.contains(v1));
         CHECK_FALSE(lt.contains(v2));
         CHECK_FALSE(lt.contains(v3));
         CHECK_FALSE(lt.contains(v4));
+        CHECK_EQ(lt.str(), "<2.0");
 
         const auto le = VersionPredicate::make_less_equal(v2);
         CHECK(le.contains(v1));
         CHECK(le.contains(v2));
         CHECK_FALSE(le.contains(v3));
         CHECK_FALSE(le.contains(v4));
+        CHECK_EQ(le.str(), "<=2.0");
 
         const auto sw = VersionPredicate::make_starts_with(v2);
         CHECK_FALSE(sw.contains(v1));
@@ -72,6 +79,7 @@ TEST_SUITE("specs::version_spec")
         CHECK(sw.contains(v201));
         CHECK_FALSE(sw.contains(v3));
         CHECK_FALSE(sw.contains(v4));
+        CHECK_EQ(sw.str(), "=2.0");
 
         const auto nsw = VersionPredicate::make_not_starts_with(v2);
         CHECK(nsw.contains(v1));
@@ -79,6 +87,7 @@ TEST_SUITE("specs::version_spec")
         CHECK_FALSE(nsw.contains(v201));
         CHECK(nsw.contains(v3));
         CHECK(nsw.contains(v4));
+        CHECK_EQ(nsw.str(), "!=2.0.*");
 
         const auto cp2 = VersionPredicate::make_compatible_with(v2, 2);
         CHECK_FALSE(cp2.contains(v1));
@@ -86,6 +95,7 @@ TEST_SUITE("specs::version_spec")
         CHECK(cp2.contains(v201));
         CHECK_FALSE(cp2.contains(v3));
         CHECK_FALSE(cp2.contains(v4));
+        CHECK_EQ(cp2.str(), "~=2.0");
 
         const auto cp3 = VersionPredicate::make_compatible_with(v2, 3);
         CHECK_FALSE(cp3.contains(v1));
@@ -93,6 +103,7 @@ TEST_SUITE("specs::version_spec")
         CHECK_FALSE(cp3.contains(v201));
         CHECK_FALSE(cp3.contains(v3));
         CHECK_FALSE(cp3.contains(v4));
+        CHECK_EQ(cp3.str(), "~=2.0.0");
 
         const auto predicates = std::array{ free, eq, ne, lt, le, gt, ge, sw, cp2, cp3 };
         for (std::size_t i = 0; i < predicates.size(); ++i)
@@ -140,6 +151,10 @@ TEST_SUITE("specs::version_spec")
             CHECK_FALSE(spec.contains(Version(0, { { { 2 } }, { { 0 } }, { { 0 } } })));  // 2.0.0
             CHECK_FALSE(spec.contains(Version(0, { { { 2 } }, { { 1 } } })));             // 2.1
             CHECK_FALSE(spec.contains(Version(0, { { { 2 } }, { { 3 } } })));             // 2.3
+
+            // Note this won't always be the same as the parsed string because of the tree
+            // serialization
+            CHECK_EQ(spec.str(), "<2.0|(>2.3,<=2.8.0)");
         }
     }
 
diff --git a/libmambapy/src/libmambapy/bindings/specs.cpp b/libmambapy/src/libmambapy/bindings/specs.cpp
index 681f361869..43a483475a 100644
--- a/libmambapy/src/libmambapy/bindings/specs.cpp
+++ b/libmambapy/src/libmambapy/bindings/specs.cpp
@@ -561,6 +561,7 @@ namespace mambapy
             .def_readonly_static("glob_suffix_token", &VersionSpec::glob_suffix_token)
             .def_static("parse", &VersionSpec::parse, py::arg("str"))
             .def("contains", &VersionSpec::contains, py::arg("point"))
+            .def("__str__", &VersionSpec::str)
             .def("__copy__", &copy<VersionSpec>)
             .def("__deepcopy__", &deepcopy<VersionSpec>, py::arg("memo"));
     }
diff --git a/libmambapy/tests/test_specs.py b/libmambapy/tests/test_specs.py
index cefaa327e3..4438c42cd1 100644
--- a/libmambapy/tests/test_specs.py
+++ b/libmambapy/tests/test_specs.py
@@ -651,5 +651,8 @@ def test_VersionSpec():
     assert not vs.contains(Version.parse("1.1"))
     assert vs.contains(Version.parse("2.1"))
 
-    # Copy
-    copy.deepcopy(vs)  # No easy comaprison
+    # str
+    assert str(vs) == ">2.0,<3.0"
+
+    # Copy, no easy comparison, this may not work for all specs
+    assert str(copy.deepcopy(vs)) == str(vs)