bpo-24160: Fix breakpoints persistence across multiple pdb sessions (GH-21989)

Lib/bdb.py

@@ -34,6 +34,8 @@ class Bdb:
         self.fncache = {}
         self.frame_returning = None
 
+        self._load_breaks()
+
     def canonic(self, filename):
         """Return canonical form of filename.
 
@@ -365,6 +367,12 @@ class Bdb:
     # Call self.get_*break*() to see the breakpoints or better
     # for bp in Breakpoint.bpbynumber: if bp: bp.bpprint().
 
+    def _add_to_breaks(self, filename, lineno):
+        """Add breakpoint to breaks, if not already there."""
+        bp_linenos = self.breaks.setdefault(filename, [])
+        if lineno not in bp_linenos:
+            bp_linenos.append(lineno)
+
     def set_break(self, filename, lineno, temporary=False, cond=None,
                   funcname=None):
         """Set a new breakpoint for filename:lineno.
@@ -377,12 +385,21 @@ class Bdb:
         line = linecache.getline(filename, lineno)
         if not line:
             return 'Line %s:%d does not exist' % (filename, lineno)
-        list = self.breaks.setdefault(filename, [])
-        if lineno not in list:
-            list.append(lineno)
+        self._add_to_breaks(filename, lineno)
         bp = Breakpoint(filename, lineno, temporary, cond, funcname)
         return None
 
+    def _load_breaks(self):
+        """Apply all breakpoints (set in other instances) to this one.
+
+        Populates this instance's breaks list from the Breakpoint class's
+        list, which can have breakpoints set by another Bdb instance. This
+        is necessary for interactive sessions to keep the breakpoints
+        active across multiple calls to run().
+        """
+        for (filename, lineno) in Breakpoint.bplist.keys():
+            self._add_to_breaks(filename, lineno)
+
     def _prune_breaks(self, filename, lineno):
         """Prune breakpoints for filename:lineno.
 
@@ -681,6 +698,12 @@ class Breakpoint:
         else:
             self.bplist[file, line] = [self]
 
+    @staticmethod
+    def clearBreakpoints():
+        Breakpoint.next = 1
+        Breakpoint.bplist = {}
+        Breakpoint.bpbynumber = [None]
+
     def deleteMe(self):
         """Delete the breakpoint from the list associated to a file:line.