Server returns snippets even though client doesn't support them

The completion request always returns snippet-type completions, even if the client initialisation request doesn't claim to support them.

Logs:

• Initialize does not include snippetSupport: true which should be interpreted as not supporting snippets (only plaintext)

2019-07-05 22:43:11,807 - DEBUG - TX: Sending message: b'Content-Length: 654\r\n\r\n{"id": "1", "jsonrpc": "2.0", "method": "initialize", "params": {"capabilities": {"textDocument": {"completion": {"completionItemKind": {"valueSet": [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25]}}, "hover": {"contentFormat": ["plaintext", "markdown"]}, "signatureHelp": {"signatureInformation": {"documentationFormat": ["plaintext", "markdown"], "parameterInformation": {"labelOffsetSupport": false}}}}}, "initializationOptions": {}, "processId": 59070, "rootPath": "/Users/ben/.vim/bundle/YouCompleteMe/third_party/ycmd/ycmd", "rootUri": "file:///Users/ben/.vim/bundle/YouCompleteMe/third_party/ycmd/ycmd"}}'

• completion request

2019-07-05 22:46:30,803 - DEBUG - TX: Sending message: b'Content-Length: 215\r\n\r\n{"id": "4", "jsonrpc": "2.0", "method": "textDocument/completion", "params": {"position": {"character": 2, "line": 0}, "textDocument": {"uri": "file:///Users/ben/Development/lsp/yaml/tests/ansible/tasks/main.yml"}}}'

• response (snipped)

2019-07-05 22:46:30,828 - DEBUG - RX: Received message: b'{"jsonrpc":"2.0","id":"4","result":{"items":[{"kind":10,"label":"shell","insertText":"shell: $1","insertTextFormat":2,"documentation":"","textEdit":{"range":{"start":{"line":0,"character":2},"end":{"line":0,"character":4}},"newText":"shell: $1"}},

Note: "insertTextFormat":2 is 'snippet' :

	/**
	 * The primary text to be inserted is treated as a snippet.
	 *
	 * A snippet can define tab stops and placeholders with `$1`, `$2`
	 * and `${3:foo}`. `$0` defines the final tab stop, it defaults to
	 * the end of the snippet. Placeholders with equal identifiers are linked,
	 * that is typing in one will update others too.
	 */
	export const Snippet = 2;

Start by tracing how initialization capabilities and completion responses are handled in the TypeScript language server. Verify the behavior against the logged initialize and textDocument/completion requests; done means clients without snippetSupport receive plaintext-compatible completions rather than insertTextFormat 2.