Export pgoutput.so imports from the main wasm module to enable logical replication slots

src/backend/replication/pgoutput/Makefile

@@ -24,9 +24,27 @@ include $(top_srcdir)/src/Makefile.shlib
 
 install: all installdirs install-lib
 
+ifeq ($(PORTNAME), emscripten)
+# pgoutput.so is loaded at runtime as an emscripten side module, but unlike
+# pgxs-built extensions it is linked from src/backend, so its imports from the
+# core module are not collected automatically. Without this, symbols used only
+# by pgoutput (e.g. logicalrep_write_*) are dead-code-eliminated from the main
+# module (-sMAIN_MODULE=2) and logical decoding fails at runtime with a call
+# to an undefined table entry. Generate the .imports file here so the
+# pglite-exported-functions target keeps these symbols alive.
+install: install-imports
+
+.PHONY: install-imports
+install-imports: all
+	$(MKDIR_P) '$(DESTDIR)$(emscripten_extension_imports_dir)'
+	find . -name "*.o" -exec $(LLVM_NM) --undefined-only {} \; | awk '{print $$2}' | sed '/^$$/d' | sort -u > '$(NAME).undef.txt'
+	find . -type f \( -name "*.o" -o -name "*.so" \) -exec $(LLVM_NM) --defined-only {} \; | awk '$$2 ~ /^[TDB]$$/ {print $$3}' | sed '/^$$/d' | sort -u > '$(NAME).defs.txt'
+	comm -23 '$(NAME).undef.txt' '$(NAME).defs.txt' > '$(DESTDIR)$(emscripten_extension_imports_dir)/$(NAME).imports'
+endif
+
 installdirs: installdirs-lib
 
 uninstall: uninstall-lib
 
 clean distclean: clean-lib
-	rm -f $(OBJS)
+	rm -f $(OBJS) $(NAME).undef.txt $(NAME).defs.txt