sphinx-agent: Use only builtin nodes for line numbers

To remove the possibility of conflicting with extensions that introduce
custom doctree nodes, the sphinx agent will only consider nodes defined
in `docutils.nodes` or `sphinx.addnodes` when injecting line numbers

lib/esbonio/changes/874.fix.md

@@ -0,0 +1 @@
+Esbonio's preview generation should no longer conflict with extensions like `ablog` which call methods like `replac_self()` on custom doctree nodes.

lib/esbonio/esbonio/sphinx_agent/handlers/webview.py

@@ -15,6 +15,7 @@
 
 
 STATIC_DIR = (pathlib.Path(__file__).parent.parent / "static").resolve()
+ALLOWED_MODULES = {"docutils.nodes", "sphinx.addnodes"}
 
 
 def has_source(node):
@@ -31,6 +32,16 @@ def has_source(node):
     if isinstance(node, addnodes.toctree) and version_info[0] < 7:
         return False
 
+    # It's not only limited to `toctreenodes`!
+    #
+    # The identical error is thrown when using esbonio with the `ablog` extension
+    # See: https://github.com/swyddfa/esbonio/issues/874
+    #
+    # I think for now, the safest approach is to only handle nodes defined by Sphinx or
+    # docutils.
+    if node.__module__ not in ALLOWED_MODULES:
+        return False
+
     return (node.line or 0) > 0 and node.source is not None