Added clipping function.

Backend/VarFunctions.py

@@ -13,9 +13,12 @@ LoopSources = ("children", "siblings", "parents")
 
 MarkerPattern = re.compile(
     r"\{(?:(?P<CrossPath>[^\s{}']+)\s+)?\*\*\*(?P<CrossName>[^\s*{}]+)"
-    r"(?:\s+(?P<CrossPipe>head|tail)\s+(?P<CrossPipeCount>\d+))?\}"
-    r"|\{(?P<PipePath>[^\s{}']+)\s+(?P<PipeMode>head|tail)\s+(?P<PipeCount>\d+)\}"
-    r"|\{(?P<LinePath>[^\s{}']+)\s+'(?P<LineNumber>\d+)'\}"
+    r"(?:\s+(?P<CrossPipe>head|tail)\s+(?P<CrossPipeCount>\d+))?"
+    r"(?:\s*\\\s*(?P<CrossClip>[^{}]*))?\}"
+    r"|\{(?P<PipePath>[^\s{}']+)\s+(?P<PipeMode>head|tail)\s+(?P<PipeCount>\d+)"
+    r"(?:\s*\\\s*(?P<PipeClip>[^{}]*))?\}"
+    r"|\{(?P<LinePath>[^\s{}']+)\s+'(?P<LineNumber>\d+)'"
+    r"(?:\s*\\\s*(?P<LineClip>[^{}]*))?\}"
     r"|\{\*\*(?P<LineName>[^\s*{}]+)\}"
     r"|\{\*(?P<BlockName>[^\s*{}]+)\}"
 )
@@ -30,6 +33,39 @@ LoopMarkerPattern = re.compile(
 )
 
 
+def _CompileClipPattern(Pattern: str) -> re.Pattern:
+    RegexParts = []
+    LastIndex = len(Pattern) - 1
+
+    for Index, Char in enumerate(Pattern):
+        IsLast = Index == LastIndex
+        if Char == "!":
+            RegexParts.append("(.*)" if IsLast else "(.*?)")
+        elif Char == "?":
+            RegexParts.append(".*" if IsLast else ".*?")
+        else:
+            RegexParts.append(re.escape(Char))
+
+    if not Pattern or Pattern[-1] not in "!?":
+        RegexParts.append(".*")
+
+    return re.compile("".join(RegexParts), re.DOTALL)
+
+
+def _ApplyClip(Value: str, Pattern: str) -> str:
+    Pattern = Pattern.strip()
+
+    if not Pattern:
+        return Value
+
+    Match = _CompileClipPattern(Pattern).match(Value)
+
+    if Match is None:
+        return Value
+
+    return "".join(Match.groups())
+
+
 def _LineBounds(Content: str, Position: int) -> tuple[int, int]:
     LineStart = Content.rfind("\n", 0, Position) + 1
     LineEnd = Content.find("\n", Position)
@@ -206,9 +242,25 @@ def _ResolveLoops(
         CloseMatch = _FindLoopClose(Matches, Index + 1, IsFixed, Key)
         BodyEnd = CloseMatch.start() if CloseMatch is not None else len(Content)
         BodyTemplate = Content[Match.end() : BodyEnd]
-        VariablePattern = re.compile(rf"%{re.escape(LoopVar)}\b")
+        EscapedVar = re.escape(LoopVar)
+        VariablePattern = re.compile(
+            r"\{%" + EscapedVar + r"\s*\\\s*(?P<Clip>[^{}]*)\}"
+            r"|%" + EscapedVar + r"\b"
+        )
 
-        Rendered = "\n".join(VariablePattern.sub(Item, BodyTemplate) for Item in Items)
+        RenderedItems = []
+        for Item in Items:
+            ItemRendered = VariablePattern.sub(
+                lambda VariableMatch, CurrentItem=Item: (
+                    _ApplyClip(CurrentItem, VariableMatch.group("Clip"))
+                    if VariableMatch.group("Clip") is not None
+                    else CurrentItem
+                ),
+                BodyTemplate,
+            )
+            RenderedItems.append(ItemRendered)
+
+        Rendered = "\n".join(RenderedItems)
 
         Output.append(Content[Cursor : Match.start()])
         Output.append(Rendered)
@@ -383,6 +435,8 @@ def ResolvePortals(
                 Replacement = _ApplyPipe(
                     Replacement, Match.group("CrossPipe"), int(Match.group("CrossPipeCount"))
                 )
+            if Replacement is not None and Match.group("CrossClip"):
+                Replacement = _ApplyClip(Replacement, Match.group("CrossClip"))
         elif Match.group("PipeMode"):
             Replacement = _ResolveWholeFilePipe(
                 RootName,
@@ -393,6 +447,8 @@ def ResolvePortals(
                 Username,
                 UserGroups,
             )
+            if Replacement is not None and Match.group("PipeClip"):
+                Replacement = _ApplyClip(Replacement, Match.group("PipeClip"))
         elif Match.group("LineNumber"):
             Replacement = _ResolveLineNumberReference(
                 RootName,
@@ -402,6 +458,8 @@ def ResolvePortals(
                 Username,
                 UserGroups,
             )
+            if Replacement is not None and Match.group("LineClip"):
+                Replacement = _ApplyClip(Replacement, Match.group("LineClip"))
 
         if Replacement is not None:
             Output.append(LocallyResolved[Cursor : Match.start()])