More details in error message when failing to parse json from a python command's output

libmamba/include/mamba/specs/build_number_spec.hpp

@@ -73,7 +73,7 @@ namespace mamba::specs
         friend auto equal(free_interval, free_interval) -> bool;
         friend auto
         operator==(const BuildNumberPredicate& lhs, const BuildNumberPredicate& rhs) -> bool;
-        friend class ::fmt::formatter<BuildNumberPredicate>;
+        friend struct ::fmt::formatter<BuildNumberPredicate>;
     };
 
     auto operator==(const BuildNumberPredicate& lhs, const BuildNumberPredicate& rhs) -> bool;
@@ -140,7 +140,7 @@ namespace mamba::specs
 
         BuildNumberPredicate m_predicate;
 
-        friend class ::fmt::formatter<BuildNumberSpec>;
+        friend struct ::fmt::formatter<BuildNumberSpec>;
     };
 
     namespace build_number_spec_literals

libmamba/include/mamba/specs/version_spec.hpp

@@ -110,7 +110,7 @@ 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>;
+        friend struct ::fmt::formatter<VersionPredicate>;
     };
 
     auto operator==(const VersionPredicate& lhs, const VersionPredicate& rhs) -> bool;
@@ -210,7 +210,7 @@ namespace mamba::specs
 
         tree_type m_tree;
 
-        friend class ::fmt::formatter<VersionSpec>;
+        friend struct ::fmt::formatter<VersionSpec>;
     };
 
     namespace version_spec_literals

libmamba/src/core/prefix_data.cpp

@@ -9,9 +9,11 @@
 #include <unordered_map>
 #include <utility>
 
+#include <fmt/ranges.h>
 #include <reproc++/run.hpp>
 
 #include "mamba/core/channel_context.hpp"
+#include "mamba/core/error_handling.hpp"
 #include "mamba/core/output.hpp"
 #include "mamba/core/prefix_data.hpp"
 #include "mamba/core/util.hpp"
@@ -223,15 +225,27 @@ namespace mamba
         reproc::options run_options;
         run_options.env.extra = reproc::env{ env };
 
+        LOG_TRACE << "Running command: "
+                  << fmt::format("{}\n  env options:{}", fmt::join(args, " "), fmt::join(env, " "));
+
         auto [status, ec] = reproc::run(
             args,
             run_options,
             reproc::sink::string(out),
             reproc::sink::string(err)
         );
+
         if (ec)
         {
-            throw std::runtime_error(ec.message());
+            const auto message = fmt::format(
+                "failed to run python command :\n  error: {}\n  command ran: {}\n  env options:{}\n-> output:\n{}\n\n-> error output:{}",
+                ec.message(),
+                fmt::join(args, " "),
+                fmt::join(env, " "),
+                out,
+                err
+            );
+            throw mamba_error{ message, mamba_error_code::internal_failure };
         }
 
         // Nothing installed with `pip`
@@ -241,7 +255,24 @@ namespace mamba
             return;
         }
 
-        nlohmann::json j = nlohmann::json::parse(out);
+        LOG_TRACE << "Parsing `pip inspect` output:\n" << out;
+        nlohmann::json j;
+        try
+        {
+            j = nlohmann::json::parse(out);
+        }
+        catch (const std::exception& ec)
+        {
+            const auto message = fmt::format(
+                "failed to parse python command output:\n  error: {}\n  command ran: {}\n  env options:{}\n-> output:\n{}\n\n-> error output:{}",
+                ec.what(),
+                fmt::join(args, " "),
+                fmt::join(env, " "),
+                out,
+                err
+            );
+            throw mamba_error{ message, mamba_error_code::internal_failure };
+        }
 
         if (j.contains("installed") && j["installed"].is_array())
         {