Properly position the cursor at the first stop in some cases when inserting snippets without editor support (talonhub#2017)

Applies when:

- there is text on the line after the inserted snippet
- the first stop in the snippet is on the last (or only) line

Also documents an assumption in `move_to_correct_column` that caused the
incorrect behavior.

Per discussion on Slack, we may want to change the behavior of
`move_to_correct_column` to not go to the end of the line, but this
involves different tradeoffs that should be discussed further.

Author: nriley

core/snippets/snippets_insert_raw_text.py

@@ -21,7 +21,21 @@
     desc="""If true, inserting snippets as raw text will always be done through pasting""",
 )
 
-RE_STOP = re.compile(r"\$(\d+|\w+)|\$\{(\d+|\w+)\}|\$\{(\d+|\w+):(.+)\}")
+RE_STOP = re.compile(
+    r"""
+    (?:\\\$) (?# Escaped $ - not a stop; skip and don't capture anything)
+    |
+    (?:
+        \$(\d+|\w+) (?# $... where ... is a captured stop number or variable)
+        |
+        \$\{(\d+|\w+)\} (?# ${...} where ... is as above)
+        |
+        \$\{(\d+|\w+):(.+)\} (?# ${...:xxx} where ... is as above and xxx a default value)
+    )
+    """,
+    re.VERBOSE,
+)
+
 LAST_SNIPPET_HOLE_KEY_VALUE = 1000
 
 
@@ -157,34 +171,40 @@ def parse_snippet(body: str):
     # Some IM services will send the message on a tab
     body = format_tabs(body)
 
-    # Replace variable with appropriate value/text
-    body = re.sub(r"\$TM_SELECTED_TEXT", lambda _: actions.edit.selected_text(), body)
-    body = re.sub(r"\$CLIPBOARD", lambda _: actions.clip.text(), body)
-
     lines = body.splitlines()
     stops: list[Stop] = []
 
     for i, line in enumerate(lines):
-        match = RE_STOP.search(line)
-
-        while match:
-            stops.append(
-                Stop(
-                    name=match.group(1) or match.group(2) or match.group(3),
-                    rows_up=len(lines) - i - 1,
-                    columns_left=0,
-                    row=i,
-                    col=match.start(),
-                )
-            )
-
-            # Remove tab stops and variables.
+        start = 0
+        while match := RE_STOP.search(line, start):
             stop_text = match.group(0)
-            default_value = match.group(4) or ""
-            line = line.replace(stop_text, default_value, 1)
-
-            # Might have multiple stops on the same line
-            match = RE_STOP.search(line)
+            if stop_text[0] == "\\":
+                # Remove escape for $
+                value = stop_text[1:]
+                # Don't match now-unescaped $ as a stop
+                start = match.end() - 1
+            else:
+                name = match.group(1) or match.group(2) or match.group(3)
+                value = match.group(4) or ""
+
+                match name:
+                    case "TM_SELECTED_TEXT":
+                        value = actions.edit.selected_text() or value
+                    case "CLIPBOARD":
+                        value = actions.clip.text() or value
+                    case _:
+                        stops.append(
+                            Stop(
+                                name=name,
+                                rows_up=len(lines) - i - 1,
+                                columns_left=0,
+                                row=i,
+                                col=match.start(),
+                            )
+                        )
+
+            # Remove/replace escaped $, tab stops and variables.
+            line = line.replace(stop_text, value, 1)
 
         # Update existing line
         lines[i] = line