testament improvement: allow inline error messages inside test cases (#15294)

* testament support for inline error messages
* adapt teffects1.nim test to show the potential

testament/specs.nim

@@ -7,8 +7,8 @@
 #    distribution, for details about the copyright.
 #
 
-import sequtils, parseutils, strutils, os, streams, parsecfg
-from hashes import hash
+import sequtils, parseutils, strutils, os, streams, parsecfg,
+  tables, hashes
 
 type TestamentData* = ref object
   # better to group globals under 1 object; could group the other ones here too
@@ -62,6 +62,11 @@ type
     targetObjC = "ObjC"
     targetJS = "JS"
 
+  InlineError* = object
+    kind*: string
+    msg*: string
+    line*, col*: int
+
   TSpec* = object
     action*: TTestAction
     file*, cmd*: string
@@ -90,6 +95,7 @@ type
     useValgrind*: bool
     timeout*: float # in seconds, fractions possible,
                     # but don't rely on much precision
+    inlineErrors*: seq[InlineError] # line information to error message
 
 proc getCmd*(s: TSpec): string =
   if s.cmd.len == 0:
@@ -116,14 +122,85 @@ when not declared(parseCfgBool):
     of "n", "no", "false", "0", "off": result = false
     else: raise newException(ValueError, "cannot interpret as a bool: " & s)
 
-proc extractSpec(filename: string): string =
-  const tripleQuote = "\"\"\""
-  var x = readFile(filename).string
-  var a = x.find(tripleQuote)
-  var b = x.find(tripleQuote, a+3)
+const
+  inlineErrorMarker = "#[tt."
+
+proc extractErrorMsg(s: string; i: int; line: var int; col: var int; spec: var TSpec): int =
+  result = i + len(inlineErrorMarker)
+  inc col, len(inlineErrorMarker)
+  var kind = ""
+  while result < s.len and s[result] in IdentChars:
+    kind.add s[result]
+    inc result
+    inc col
+
+  var caret = (line, -1)
+
+  template skipWhitespace =
+    while result < s.len and s[result] in Whitespace:
+      if s[result] == '\n':
+        col = 1
+        inc line
+      else:
+        inc col
+      inc result
+
+  skipWhitespace()
+  if result < s.len and s[result] == '^':
+    caret = (line-1, col)
+    inc result
+    inc col
+    skipWhitespace()
+
+  var msg = ""
+  while result < s.len-1:
+    if s[result] == '\n':
+      inc result
+      inc line
+      col = 1
+    elif s[result] == ']' and s[result+1] == '#':
+      while msg.len > 0 and msg[^1] in Whitespace:
+        setLen msg, msg.len - 1
+
+      inc result
+      inc col, 2
+      if kind == "Error": spec.action = actionReject
+      spec.unjoinable = true
+      spec.inlineErrors.add InlineError(kind: kind, msg: msg, line: caret[0], col: caret[1])
+      break
+    else:
+      msg.add s[result]
+      inc result
+      inc col
+
+proc extractSpec(filename: string; spec: var TSpec): string =
+  const
+    tripleQuote = "\"\"\""
+  var s = readFile(filename).string
+
+  var i = 0
+  var a = -1
+  var b = -1
+  var line = 1
+  var col = 1
+  while i < s.len:
+    if s.continuesWith(tripleQuote, i):
+      if a < 0: a = i
+      elif b < 0: b = i
+      inc i, 2
+      inc col
+    elif s[i] == '\n':
+      inc line
+      col = 1
+    elif s.continuesWith(inlineErrorMarker, i):
+      i = extractErrorMsg(s, i, line, col, spec)
+    else:
+      inc col
+    inc i
+
   # look for """ only in the first section
   if a >= 0 and b > a and a < 40:
-    result = x.substr(a+3, b-1).replace("'''", tripleQuote)
+    result = s.substr(a+3, b-1).replace("'''", tripleQuote)
   else:
     #echo "warning: file does not contain spec: " & filename
     result = ""
@@ -160,7 +237,7 @@ proc isCurrentBatch(testamentData: TestamentData, filename: string): bool =
 
 proc parseSpec*(filename: string): TSpec =
   result.file = filename
-  let specStr = extractSpec(filename)
+  let specStr = extractSpec(filename, result)
   var ss = newStringStream(specStr)
   var p: CfgParser
   open(p, ss, filename, 1)