Merge remote-tracking branch 'origin/master' into flakes

src/libutil/error.hh

@@ -1,107 +1,92 @@
-#ifndef error_hh
-#define error_hh
+#pragma once
 
-#include "ansicolor.hh"
-#include <string>
-#include <optional>
-#include <iostream>
+
+#include "ref.hh"
 #include "types.hh"
 
-namespace nix
-{
+#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 {
-    elWarning,
-    elError
-} ErrLevel;
+    lvlError = 0,
+    lvlWarn,
+    lvlInfo,
+    lvlTalkative,
+    lvlChatty,
+    lvlDebug,
+    lvlVomit
+} Verbosity;
 
-struct ErrPos
-{
-    int lineNumber;
-    int column;
-    string nixFile;
+// 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)
     {
-        lineNumber = pos.line;
+        line = pos.line;
         column = pos.column;
-        nixFile = pos.file;
+        file = pos.file;
         return *this;
     }
 
     template <class P>
     ErrPos(const P &p)
     {
-      *this = p;
+        *this = p;
     }
 };
 
-struct NixCode
-{
+struct NixCode {
     ErrPos errPos;
     std::optional<string> prevLineOfCode;
-    string errLineOfCode;
+    std::optional<string> errLineOfCode;
     std::optional<string> nextLineOfCode;
 };
 
-// ----------------------------------------------------------------
-// format function for hints.  same as fmt, except templated values
-// are always in yellow.
-
-template <class T>
-struct yellowify
-{
-    yellowify(T &s) : value(s) {}
-    T &value;
-};
-
-template <class T>
-std::ostream& operator<<(std::ostream &out, const yellowify<T> &y)
-{
-    return out << ANSI_YELLOW << y.value << ANSI_NORMAL;
-}
-
-class hintformat
-{
-public:
-    hintformat(string format) :fmt(format)
-    {
-        fmt.exceptions(boost::io::all_error_bits ^ boost::io::too_many_args_bit);
-    }
-    template<class T>
-    hintformat& operator%(const T &value)
-    {
-        fmt % yellowify(value);
-        return *this;
-    }
-
-    std::string str() const
-    {
-        return fmt.str();
-    }
-
-    template <typename U>
-    friend class AddHint;
-private:
-    format fmt;
-};
-
-std::ostream& operator<<(std::ostream &os, const hintformat &hf);
-
-template<typename... Args>
-inline hintformat hintfmt(const std::string & fs, const Args & ... args)
-{
-    hintformat f(fs);
-    formatHelper(f, args...);
-    return f;
-}
-
-// -------------------------------------------------
-// ErrorInfo.
-struct ErrorInfo
-{
-    ErrLevel level;
+struct ErrorInfo {
+    Verbosity level;
     string name;
     string description;
     std::optional<hintformat> hint;
@@ -110,12 +95,93 @@ struct ErrorInfo
     static std::optional<string> programName;
 };
 
-// --------------------------------------------------------
-// error printing
+std::ostream& operator<<(std::ostream &out, const ErrorInfo &einfo);
 
-// just to cout for now.
-void printErrorInfo(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);
+MakeError(UsageError, Error);
+
+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"; }
+};
 
 }
-
-#endif