[sonic-db-cli] Support --json option

[bgallagher-nexthop]

Fixes #1204

Background

$> sonic-db-cli STATE_DB HGETALL "TRANSCEIVER_VDM_REAL_VALUE|Ethernet16" | jq
jq: parse error: Invalid numeric literal at line 1, column 28

sonic-db-cli does not output valid JSON, because it is designed to output the Python repr() representation of a dictionary. This means it does not work with tools like jq to format the output in a more readable manner.

Changes

This PR addresses that problem by introducing a new CLI option to sonic-db-cli: --json or -j. This causes sonic-db-cli to output valid JSON that is usable with tools like jq without breaking any backwards compatibility with users or tooling that relies on sonic-db-cli's current output format.

Testing

New unit-tests have been written.

Tested manually on a network switch:

~$ sonic-db-cli --json STATE_DB HGETALL "TRANSCEIVER_DOM_REAL_VALUE|Ethernet440" | jq
{}
~$ sonic-db-cli --json STATE_DB HGETALL "TRANSCEIVER_INFO|Ethernet440" | jq
{
  "media_interface_technology": "Copper cable unequalized",
  "manufacturer": "Amphenol",
  "ext_rateselect_compliance": "N/A",
  "cmis_rev": "5.0",
  "host_lane_count": "8",
....
}
~$ sonic-db-cli --json STATE_DB HGETALL "TRANSCEIVER_STATUS|Ethernet440" | jq
{
  "module_state": "ModuleReady",
  "module_fault_cause": "No Fault detected",
  "last_update_time": "Wed Jun 10 16:59:03 2026"
}
~$ sonic-db-cli --json STATE_DB KEYS "TRANSCEIVER_STATUS" | jq
[]
~$ sonic-db-cli --json STATE_DB KEYS "TRANSCEIVER_INFO*" | jq
[
  "TRANSCEIVER_INFO|Ethernet416",
  "TRANSCEIVER_INFO|Ethernet384",
  "TRANSCEIVER_INFO|Ethernet424",
  "TRANSCEIVER_INFO|Ethernet432",
  "TRANSCEIVER_INFO|Ethernet408",
  "TRANSCEIVER_INFO|Ethernet400",
  "TRANSCEIVER_INFO|Ethernet392",
  "TRANSCEIVER_INFO|Ethernet440"
]

[mssonicbld]

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[bgallagher-nexthop]

#1206 & sonic-net/sonic-buildimage#27836 are published to fix the build failure on this PR (it's a breakage on master).

[Copilot]

Pull request overview

This PR adds an optional JSON output mode to sonic-db-cli so command results can be consumed by JSON tools (e.g., jq) without changing the existing default output format used by current tooling.

Changes:

• Add -j/--json CLI flag and plumb it through command execution to select JSON formatting.
• Implement swss::RedisReply::to_json_string() to serialize hiredis replies into valid JSON (with HGETALL / HSCAN field-maps as JSON objects).
• Add unit tests for JSON output and update the CLI help golden output.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
tests/cli_ut.cpp	Adds coverage validating JSON formatting across several Redis reply types.
tests/cli_test_data/cli_help_output.txt	Updates expected sonic-db-cli help text to include --json.
sonic-db-cli/sonic-db-cli.h	Extends Options and executeCommands() signature to carry JSON mode.
sonic-db-cli/sonic-db-cli.cpp	Implements -j/--json parsing and switches output formatting based on the flag.
common/redisreply.h	Declares new RedisReply::to_json_string() API.
common/redisreply.cpp	Implements JSON conversion logic using nlohmann JSON.

Comments suppressed due to low confidence (1)

sonic-db-cli/sonic-db-cli.cpp:238

• --namespace is declared with optional_argument, so --namespace=asic0 will set optarg, but the current parsing ignores optarg and instead consumes the next argv token (db_or_op) as the namespace. This breaks a valid getopt_long invocation form.

                case 'j':
                    options.m_json = true;
                    break;

                case 'n':
                    if (optind < argc)
                    {
                        options.m_namespace = argv[optind];
                        optind++;
                    }
                    else
                    {
                        throw invalid_argument("namespace value is missing.");
                    }
                    break;

[mssonicbld]

Hi, there are workflow run(s) waiting for approval, you may be first-time contributor. I will notify maintainers to help approve once PR is approved. Thanks!

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