1 files changed, 105 insertions, 0 deletions
diff --git a/krebs/5pkgs/simple/nixos-format-error.nix b/krebs/5pkgs/simple/nixos-format-error.nix
new file mode 100644
index 000000000..14066efb1
--- /dev/null
+++ b/krebs/5pkgs/simple/nixos-format-error.nix
@@ -0,0 +1,105 @@
+{ pkgs }:
+
+pkgs.writeGawk "nixos-format-error" ''
+  # usage: nixos-rebuild ... 2>&1 | nixos-format-error
+
+  function out() {
+    print
+    next
+  }
+
+  BEGIN {
+    IDLE = 0
+    ACTIVE = 1
+    PASSIVE = 2
+    ERROR = 3
+
+    start_state = IDLE
+
+    state = start_state
+  }
+
+  END {
+    if (trace_count)
+      for (i = trace_count - 1; i >= 0; i--)
+        print trace[i]
+  }
+
+  state == PASSIVE {
+    out()
+  }
+
+  state == IDLE {
+    if ($0 == "building the system configuration...") {
+      state = ACTIVE
+    }
+    out()
+  }
+
+  state == ACTIVE {
+    if ($1 == "error:") {
+      state = ERROR
+      sub(/^/,"\x1b[31;1m"); sub(/$/,"\x1b[m")
+      trace[trace_count++] = $0
+
+      "stty -F /dev/tty size" |& getline
+      COLUMNS = gensub(/.* ([0-9]+)$/, "\\1", "1")
+
+      next
+    }
+    if ($0 ~ /^these [0-9]+ derivations will be built:/) {
+      state = PASSIVE
+    }
+    if ($0 == "activating the configuration...") {
+      state = PASSIVE
+    }
+    out()
+  }
+
+  state == ERROR {
+
+    if ($0 ~ /^\s*at /) {
+      location = gensub(/^\s*at (.*):$/,"\\1","1")
+      content = ""
+      lnumcol = gensub(/^.*:([0-9]+:[0-9]+)$/,"\\1","1",location)
+      lnum = gensub(/:.*/,"","1",lnumcol)
+      col = gensub(/.*:/,"","1",lnumcol)
+      next
+    }
+
+    if ($1 == lnum "|") {
+      content = gensub(/^\s*[0-9]+\|(.*)/,"\\1","1")
+
+      location = sprintf("%50s", location)
+
+      preview_size = COLUMNS - length(location " ")
+
+      prefix = gensub(/^\s*/,"","1",substr(content, 1, col))
+      infix = gensub(/^([0-9a-zA-Z]+|.).*$/, "\\1", "1", substr(content, col + 1))
+      suffix = substr(content, col + length(infix) + 1)
+
+      if (length(prefix infix suffix) > preview_size) {
+        n = (preview_size - length(infix)) / 2 - length(" ")
+        prefix = substr(prefix, length(prefix) - n + 1)
+        if (prefix != "") { prefix = "…" prefix }
+        suffix = substr(suffix, 1, n)
+        if (suffix != "") { suffix = suffix "…" }
+      }
+
+      preview = \
+        "\x1b[38;5;244m" prefix "\x1b[m" \
+        "\x1b[38;5;230m" infix "\x1b[m" \
+        "\x1b[38;5;244m" suffix "\x1b[m"
+
+      trace[trace_count++] = location " " preview
+      next
+    }
+
+    if ($0 == "") next
+    if ($0 ~ /^\s*… (from|while)/) next
+    if ($0 ~ /^\s*([0-9]*)\|/) next
+
+    trace[trace_count++] = $0
+    next
+  }
+''