1 files changed, 146 insertions, 0 deletions
diff --git a/src/libutil/error.cc b/src/libutil/error.cc
new file mode 100644
index 000000000..a5571d4ec
--- /dev/null
+++ b/src/libutil/error.cc
@@ -0,0 +1,146 @@
+#include "error.hh"
+
+#include <iostream>
+#include <optional>
+
+namespace nix
+{
+
+std::optional<string> ErrorInfo::programName = std::nullopt;
+
+std::ostream& operator<<(std::ostream &os, const hintformat &hf)
+{
+    return os << hf.str();
+}
+
+string showErrPos(const ErrPos &errPos)
+{
+    if (errPos.column > 0) {
+        return fmt("(%1%:%2%)", errPos.lineNumber, errPos.column);
+    } else {
+        return fmt("(%1%)", errPos.lineNumber);
+    };
+}
+
+void printCodeLines(const string &prefix, const NixCode &nixCode)
+{
+    // previous line of code.
+    if (nixCode.prevLineOfCode.has_value()) {
+        std::cout << fmt("%1% %|2$5d|| %3%",
+                         prefix,
+                         (nixCode.errPos.lineNumber - 1),
+                         *nixCode.prevLineOfCode)
+                  << std::endl;
+    }
+
+    // line of code containing the error.%2$+5d%
+    std::cout << fmt("%1% %|2$5d|| %3%",
+                     prefix,
+                     (nixCode.errPos.lineNumber),
+                     nixCode.errLineOfCode)
+              << std::endl;
+
+    // error arrows for the column range.
+    if (nixCode.errPos.column > 0) {
+        int start = nixCode.errPos.column;
+        std::string spaces;
+        for (int i = 0; i < start; ++i) {
+            spaces.append(" ");
+        }
+
+        std::string arrows("^");
+
+        std::cout << fmt("%1%      |%2%" ANSI_RED "%3%" ANSI_NORMAL,
+                         prefix,
+                         spaces,
+                         arrows) << std::endl;
+    }
+
+    // next line of code.
+    if (nixCode.nextLineOfCode.has_value()) {
+        std::cout << fmt("%1% %|2$5d|| %3%",
+                         prefix,
+                         (nixCode.errPos.lineNumber + 1),
+                         *nixCode.nextLineOfCode)
+                  << std::endl;
+    }
+}
+
+void printErrorInfo(const ErrorInfo &einfo)
+{
+    int errwidth = 80;
+    string prefix = "    ";
+
+    string levelString;
+    switch (einfo.level) {
+    case ErrLevel::elError: {
+        levelString = ANSI_RED;
+        levelString += "error:";
+        levelString += ANSI_NORMAL;
+        break;
+    }
+    case ErrLevel::elWarning: {
+        levelString = ANSI_YELLOW;
+        levelString += "warning:";
+        levelString += ANSI_NORMAL;
+        break;
+    }
+    default: {
+        levelString = fmt("invalid error level: %1%", einfo.level);
+        break;
+    }
+    }
+
+    int ndl = prefix.length() + levelString.length() + 3 + einfo.name.length() + einfo.programName.value_or("").length();
+    int dashwidth = ndl > (errwidth - 3) ? 3 : errwidth - ndl;
+
+    string dashes;
+    for (int i = 0; i < dashwidth; ++i)
+        dashes.append("-");
+
+    // divider.
+    std::cout << fmt("%1%%2%" ANSI_BLUE " %3% %4% %5% %6%" ANSI_NORMAL,
+                     prefix,
+                     levelString,
+                     "---",
+                     einfo.name,
+                     dashes,
+                     einfo.programName.value_or(""))
+              << std::endl;
+
+    // filename.
+    if (einfo.nixCode.has_value()) {
+        if (einfo.nixCode->errPos.nixFile != "") {
+            string eline = einfo.nixCode->errLineOfCode != ""
+                           ? string(" ") + showErrPos(einfo.nixCode->errPos)
+                           : "";
+
+            std::cout << fmt("%1%in file: " ANSI_BLUE "%2%%3%" ANSI_NORMAL,
+                             prefix, 
+                             einfo.nixCode->errPos.nixFile,
+                             eline) << std::endl;
+            std::cout << prefix << std::endl;
+        } else {
+            std::cout << fmt("%1%from command line argument", prefix) << std::endl;
+            std::cout << prefix << std::endl;
+        }
+    }
+
+    // description
+    std::cout << prefix << einfo.description << std::endl;
+    std::cout << prefix << std::endl;
+
+    // lines of code.
+    if (einfo.nixCode->errLineOfCode != "") {
+        printCodeLines(prefix, *einfo.nixCode);
+        std::cout << prefix << std::endl;
+    }
+
+    // hint
+    if (einfo.hint.has_value()) {
+        std::cout << prefix << *einfo.hint << std::endl;
+        std::cout << prefix << std::endl;
+    }
+}
+
+}