1 files changed, 186 insertions, 0 deletions
diff --git a/src/libutil/error.hh b/src/libutil/error.hh
new file mode 100644
index 000000000..1e6102ce1
--- /dev/null
+++ b/src/libutil/error.hh
@@ -0,0 +1,186 @@
+#pragma once
+
+
+#include "ref.hh"
+#include "types.hh"
+
+#include <cstring>
+#include <list>
+#include <memory>
+#include <map>
+#include <optional>
+
+#include "fmt.hh"
+
+/* Before 4.7, gcc's std::exception uses empty throw() specifiers for
+ * its (virtual) destructor and what() in c++11 mode, in violation of spec
+ */
+#ifdef __GNUC__
+#if __GNUC__ < 4 || (__GNUC__ == 4 && __GNUC_MINOR__ < 7)
+#define EXCEPTION_NEEDS_THROW_SPEC
+#endif
+#endif
+
+namespace nix {
+
+/*
+
+This file defines two main structs/classes used in nix error handling.
+
+ErrorInfo provides a standard payload of error information, with conversion to string
+happening in the logger rather than at the call site.
+
+BaseError is the ancestor of nix specific exceptions (and Interrupted), and contains
+an ErrorInfo.
+
+ErrorInfo structs are sent to the logger as part of an exception, or directly with the
+logError or logWarning macros.
+
+See the error-demo.cc program for usage examples.
+
+*/
+
+typedef enum {
+    lvlError = 0,
+    lvlWarn,
+    lvlInfo,
+    lvlTalkative,
+    lvlChatty,
+    lvlDebug,
+    lvlVomit
+} Verbosity;
+
+// ErrPos indicates the location of an error in a nix file.
+struct ErrPos {
+    int line = 0;
+    int column = 0;
+    string file;
+
+    operator bool() const
+    {
+        return line != 0;
+    }
+
+    // convert from the Pos struct, found in libexpr.
+    template <class P>
+    ErrPos& operator=(const P &pos)
+    {
+        line = pos.line;
+        column = pos.column;
+        file = pos.file;
+        return *this;
+    }
+
+    template <class P>
+    ErrPos(const P &p)
+    {
+        *this = p;
+    }
+};
+
+struct NixCode {
+    ErrPos errPos;
+    std::optional<string> prevLineOfCode;
+    std::optional<string> errLineOfCode;
+    std::optional<string> nextLineOfCode;
+};
+
+struct ErrorInfo {
+    Verbosity level;
+    string name;
+    string description;
+    std::optional<hintformat> hint;
+    std::optional<NixCode> nixCode;
+
+    static std::optional<string> programName;
+};
+
+std::ostream& operator<<(std::ostream &out, const ErrorInfo &einfo);
+
+/* BaseError should generally not be caught, as it has Interrupted as
+   a subclass. Catch Error instead. */
+class BaseError : public std::exception
+{
+protected:
+    string prefix_; // used for location traces etc.
+    mutable ErrorInfo err;
+
+    mutable std::optional<string> what_;
+    const string& calcWhat() const;
+
+public:
+    unsigned int status = 1; // exit status
+
+    template<typename... Args>
+    BaseError(unsigned int status, const Args & ... args)
+        : err { .level = lvlError,
+                .hint = hintfmt(args...)
+              }
+        , status(status)
+    { }
+
+    template<typename... Args>
+    BaseError(const std::string & fs, const Args & ... args)
+        : err { .level = lvlError,
+                .hint = hintfmt(fs, args...)
+              }
+    { }
+
+    BaseError(hintformat hint)
+        : err { .level = lvlError,
+                .hint = hint
+              }
+    { }
+
+    BaseError(ErrorInfo && e)
+        : err(std::move(e))
+    { }
+
+    BaseError(const ErrorInfo & e)
+        : err(e)
+    { }
+
+    virtual const char* sname() const { return "BaseError"; }
+
+#ifdef EXCEPTION_NEEDS_THROW_SPEC
+    ~BaseError() throw () { };
+    const char * what() const throw () { return calcWhat().c_str(); }
+#else
+    const char * what() const noexcept override { return calcWhat().c_str(); }
+#endif
+
+    const string & msg() const { return calcWhat(); }
+    const string & prefix() const { return prefix_; }
+    BaseError & addPrefix(const FormatOrString & fs);
+
+    const ErrorInfo & info() { calcWhat(); return err; }
+};
+
+#define MakeError(newClass, superClass) \
+    class newClass : public superClass                  \
+    {                                                   \
+    public:                                             \
+        using superClass::superClass;                   \
+        virtual const char* sname() const override { return #newClass; } \
+    }
+
+MakeError(Error, BaseError);
+
+class SysError : public Error
+{
+public:
+    int errNo;
+
+    template<typename... Args>
+    SysError(const Args & ... args)
+      :Error("")
+    {
+        errNo = errno;
+        auto hf = hintfmt(args...);
+        err.hint = hintfmt("%1%: %2%", normaltxt(hf.str()), strerror(errNo));
+    }
+
+    virtual const char* sname() const override { return "SysError"; }
+};
+
+}