Reimplement cli hints based on command arg docs (#10515)

Now that the command argument specs are available at runtime (#9656), this PR addresses
#8084 by implementing a complete solution for command-line hinting in `redis-cli`.

It correctly handles nearly every case in Redis's complex command argument definitions, including
`BLOCK` and `ONEOF` arguments, reordering of optional arguments, and repeated arguments
(even when followed by mandatory arguments). It also validates numerically-typed arguments.
It may not correctly handle all possible combinations of those, but overall it is quite robust.

Arguments are only matched after the space bar is typed, so partial word matching is not
supported - that proved to be more confusing than helpful. When the user's current input
cannot be matched against the argument specs, hinting is disabled.

Partial support has been implemented for legacy (pre-7.0) servers that do not support
`COMMAND DOCS`, by falling back to a statically-compiled command argument table.
On startup, if the server does not support `COMMAND DOCS`, `redis-cli` will now issue
an `INFO SERVER` command to retrieve the server version (unless `HELLO` has already
been sent, in which case the server version will be extracted from the reply to `HELLO`).
The server version will be used to filter the commands and arguments in the command table,
removing those not supported by that version of the server. However, the static table only
includes core Redis commands, so with a legacy server hinting will not be supported for
module commands. The auto generated help.h and the scripts that generates it are gone.

Command and argument tables for the server and CLI use different structs, due primarily
to the need to support different runtime data. In order to generate code for both, macros
have been added to `commands.def` (previously `commands.c`) to make it possible to
configure the code generation differently for different use cases (one linked with redis-server,
and one with redis-cli).

Also adding a basic testing framework for the command hints based on new (undocumented)
command line options to `redis-cli`: `--test_hint 'INPUT'` prints out the command-line hint for
a given input string, and `--test_hint_file <filename>` runs a suite of test cases for the hinting
mechanism. The test suite is in `tests/assets/test_cli_hint_suite.txt`, and it is run from
`tests/integration/redis-cli.tcl`.

Co-authored-by: Oran Agra <oran@redislabs.com>
Co-authored-by: Viktor Söderqvist <viktor.soderqvist@est.tech>

1 files changed, 46 insertions, 0 deletions

diff --git a/src/cli_commands.h b/src/cli_commands.h
new file mode 100644
index 000000000..eb5a476e3
--- /dev/null
+++ b/src/cli_commands.h
@@ -0,0 +1,46 @@
+/* This file is used by redis-cli in place of server.h when including commands.c
+ * It contains alternative structs which omit the parts of the commands table
+ * that are not suitable for redis-cli, e.g. the command proc. */
+
+#ifndef __REDIS_CLI_COMMANDS_H
+#define __REDIS_CLI_COMMANDS_H
+
+#include <stddef.h>
+#include "commands.h"
+
+/* Syntax specifications for a command argument. */
+typedef struct cliCommandArg {
+    char *name;
+    redisCommandArgType type;
+    char *token;
+    char *since;
+    int flags;
+    int numsubargs;
+    struct cliCommandArg *subargs;
+    const char *display_text;
+
+    /*
+     * For use at runtime.
+     * Fields used to keep track of input word matches for command-line hinting.
+     */
+    int matched;  /* How many input words have been matched by this argument? */
+    int matched_token;  /* Has the token been matched? */
+    int matched_name;  /* Has the name been matched? */
+    int matched_all;  /* Has the whole argument been consumed (no hint needed)? */
+} cliCommandArg;
+
+/* Command documentation info used for help output */
+struct commandDocs {
+    char *name;
+    char *summary;
+    char *group;
+    char *since;
+    int numargs;
+    cliCommandArg *args; /* An array of the command arguments. */
+    struct commandDocs *subcommands;
+    char *params; /* A string describing the syntax of the command arguments. */
+};
+
+extern struct commandDocs redisCommandTable[];
+
+#endif