Case 1: ALL TABLES pub case:
-----------------------------------------

Pub:
CREATE TABLE t1 (a int) PARTITION BY RANGE (a);
CREATE TABLE t1_part1 PARTITION OF t1 FOR VALUES FROM (1) TO (10);
CREATE TABLE t1_part2 PARTITION OF t1 FOR VALUES FROM (11) TO (20);

create publication pub1 for all tables;

Sub: (individual tables)
CREATE TABLE t1 (a int);
CREATE TABLE t1_part1(a int);
CREATE TABLE t1_part2(a int);

create subscription sub1 connection 'dbname=postgres host=localhost user=shveta port=5433' publication pub1;

Pub:
INSERT INTO t1 VALUES (5), (15);

Sub: (replicated to sub)
postgres=# select * from t1_part1;
 a 
---
 5
(1 row)

postgres=# select * from t1_part2;
 a  
----
 15
(1 row)



Now block DETACH PARTITION and check:

Pub:
Session A:
BEGIN;
  SELECT * FROM t1;
  --do not commit

Session B:
--This blocks on 'A' post detach but before making some catalog changes
ALTER TABLE t1 DETACH PARTITION t1_part1 CONCURRENTLY;


Session C, while B is blocked:
postgres=# SELECT inhdetachpending FROM pg_inherits WHERE inhrelid = 't1_part1'::regclass;
 inhdetachpending 
------------------
 t

--cannot run INSERT through t1 for detached ptn: expected
postgres=# INSERT INTO t1 VALUES (6), (16);
ERROR:  no partition of relation "t1" found for row
DETAIL:  Partition key of the failing row contains (a) = (6).


--try usign ptn-name for detached ptn
INSERT INTO t1_part1 VALUES (6);
INSERT INTO t1 VALUES (16);


Sub: (both t1_part1 and t1 are replicated): as pub was on ALL TABLES.
postgres=# select * from t1_part1;
 a 
---
 5
 6
(2 rows)

postgres=# select * from t1_part2;
 a  
----
 15
 16
(2 rows)


Session C, while B is blocked, check ptn-root:
postgres=# select pg_partition_root('t1_part1');
 pg_partition_root 
-------------------
 t1_part1
(1 row)

postgres=# select pg_partition_root('t1_part2');
 pg_partition_root 
-------------------
 t1
(1 row)

pg_pub_rel and pg_pub_tables output for reference.
postgres=#  SELECT pr.oid, pr.prpubid, pub.pubname,  c.relname AS table_name FROM pg_publication_rel pr JOIN pg_class c ON c.oid = pr.prrelid JOIN pg_namespace n ON n.oid = c.relnamespace JOIN pg_publication pub ON pub.oid = pr.prpubid;
 
 oid | prpubid | pubname | table_name 
-----+---------+---------+------------
(0 rows)

postgres=# select * from pg_publication_tables;
 pubname | schemaname | tablename | attnames | rowfilter 
---------+------------+-----------+----------+-----------
 pub1    | public     | t1_part1  | {a}      | 
 pub1    | public     | t1_part2  | {a}      | 
(2 rows)







-----------------------------------------
CASE 2: ptn-table pub case:
-----------------------------------------
Pub:
CREATE TABLE t1 (a int) PARTITION BY RANGE (a);
CREATE TABLE t1_part1 PARTITION OF t1 FOR VALUES FROM (1) TO (10);
CREATE TABLE t1_part2 PARTITION OF t1 FOR VALUES FROM (11) TO (20);

create publication pub1 for table t1;

Sub: (individual tables)
CREATE TABLE t1 (a int);
CREATE TABLE t1_part1(a int);
CREATE TABLE t1_part2(a int);

create subscription sub1 connection 'dbname=postgres host=localhost user=shveta port=5433' publication pub1;


Pub:
INSERT INTO t1 VALUES (5), (15);

Sub:
postgres=# select * from t1_part1;
 a 
---
 5
(1 row)

postgres=# select * from t1_part2;
 a  
----
 15
(1 row)


Now block DETACH PARTITION and check:

Pub:
Session A:
BEGIN;
  SELECT * FROM t1;
  --do not commit

Session B:
--This blocks on 'A' post detach but before making some catalog changes
ALTER TABLE t1 DETACH PARTITION t1_part1 CONCURRENTLY;


Session C, while B is blocked:
postgres=# SELECT inhdetachpending FROM pg_inherits WHERE inhrelid = 't1_part1'::regclass;
 inhdetachpending 
------------------
 t

INSERT INTO t1_part1 VALUES (6);
INSERT INTO t1 VALUES (16);

INSERT INTO t1_part1 VALUES (7);
INSERT INTO t1 VALUES (17);


Sub: (detached ptn is also replicated even though it is not part of pg_publication_tables)
postgres=# select * from t1_part1;
 a 
---
 5
 6
 7
(3 rows)

postgres=# select * from t1_part2;
 a  
----
 15
 16
 17
(3 rows)

--pg_publication_rel entry
postgres=#  SELECT pr.oid, pr.prpubid, pub.pubname,  c.relname AS table_name FROM pg_publication_rel pr JOIN pg_class c ON c.oid = pr.prrelid JOIN pg_namespace n ON n.oid = c.relnamespace JOIN pg_publication pub ON pub.oid = pr.prpubid;
 
  oid  | prpubid | pubname | table_name 
-------+---------+---------+------------
 16394 |   16393 | pub1    | t1
(1 row)

postgres=# select * from pg_publication_tables;
 pubname | schemaname | tablename | attnames | rowfilter 
---------+------------+-----------+----------+-----------
 pub1    | public     | t1_part2  | {a}      | 
(1 row)


Once detach session is finished:
SESSION A: COMMIT

This will make SESSION B's DETACH proceed.

After that, on SESSION C:
INSERT INTO t1_part1 VALUES (9); INSERT INTO t1 VALUES (19);

t1_part1 is not replicated (expected) while t1_part2 is replicated.

SUB:
postgres=# select * from t1_part1;
 a 
---
 5
 6
 7
(3 rows)

postgres=# select * from t1_part2;
 a  
----
 15
 16
 17
 19
(4 rows)