Add diagnostic_logger

include/cppast/parser.hpp

@@ -11,6 +11,39 @@
 namespace cppast
 {
     class cpp_entity_index;
+    class diagnostic;
+
+    /// Base class for a [cppast::diagnostic]() logger.
+    ///
+    /// Its task is controlling how diagnostic are being displayed.
+    class diagnostic_logger
+    {
+    public:
+        diagnostic_logger() noexcept                = default;
+        diagnostic_logger(const diagnostic_logger&) = delete;
+        diagnostic_logger& operator=(const diagnostic_logger&) = delete;
+        virtual ~diagnostic_logger() noexcept                  = default;
+
+        /// \effects Logs the diagnostic by invoking the `do_log()` member function.
+        /// \returns Whether or not the diagnostic was logged.
+        /// \notes `source` points to a string literal that gives additional context to what generates the message.
+        bool log(const char* source, const diagnostic& d) const
+        {
+            return do_log(source, d);
+        }
+
+    private:
+        virtual bool do_log(const char* source, const diagnostic& d) const = 0;
+    };
+
+    /// A [cppast::diagnostic_logger]() that logs to `stderr`.
+    ///
+    /// It prints all diagnostics in an implementation-defined format.
+    class stderr_diagnostic_logger final : public diagnostic_logger
+    {
+    private:
+        bool do_log(const char* source, const diagnostic& d) const override;
+    };
 
     /// Base class for a parser.
     ///
@@ -33,13 +66,24 @@ namespace cppast
         }
 
     protected:
-        parser() = default;
+        /// \effects Creates it giving it a reference to the logger it uses.
+        explicit parser(type_safe::object_ref<const diagnostic_logger> logger) : logger_(logger)
+        {
+        }
+
+        /// \returns A reference to the logger used.
+        const diagnostic_logger& logger() const noexcept
+        {
+            return *logger_;
+        }
 
     private:
         /// \effects Parses the given file.
         /// \returns The [cppast::cpp_file]() object describing it.
         virtual std::unique_ptr<cpp_file> do_parse(const cpp_entity_index& idx, std::string path,
                                                    const compile_config& config) const = 0;
+
+        type_safe::object_ref<const diagnostic_logger> logger_;
     };
 } // namespace cppast