[JavaScript][Perf] Optimize speed to generate sdk

[JialinHuang803]

[lirenhe]

Do you have any data about how much time it takes to build some large RP, e.g. Compute, Network, AppService, etc.?

[JialinHuang803]

The recorded time for the Generate SDK job is as follows:
Network - 46m28s
SQL - 29m59s
Compute - 12m57s

[lirenhe]

Let's target to reduce the total time within 10 min for those RPs, looks there is a big gap especially for Network.

[kazrael2119]

time for the generation in codegen smoke test:
network: 22.93 minutes

[lirenhe]

cc @maorleger as @xirzec mentioned you are looking at some refactor of the current JS emitter which would also contribute to the performance improvement of the emitter.

[JialinHuang803]

Baseline: tsp compile timing breakdown for two large management-plane services

Ran npx tsp compile client.tsp --emit=@azure-tools/typespec-ts against the current main of @azure-tools/typespec-ts (v0.53.3), linked into azure-rest-api-specs via file:, with per-phase console.time instrumentation inside $onEmit.

Specs used:

• Network — specification/network/resource-manager/Microsoft.Network/Network/client.tsp → sdk/network/arm-network2 (1460 files, 251 warnings)
• Compute — specification/compute/resource-manager/Microsoft.Compute/Compute/client.tsp → sdk/compute/arm-compute2 (534 files, 138 warnings)

Per-phase onEmit timing

Phase	Network	Compute
create context	25.624s	13.825s
load static helpers	800.117ms	615.879ms
provide binder	45.518ms	16.609ms
build RLC code models	3.543s	1.032s
transform modular emitter options	0.181ms	0.090ms
emit logger file	10.894ms	8.112ms
emit models - emitTypes	5:36.832	41.720s
emit models - emitNonModelResponseTypes	192.512ms	31.663ms
emit models (total)	5:37.026	41.753s
build models subpath index	6.527s	6.411s
get client hierarchy map	0.070ms	0.044ms
Client - renameClientName	0.163ms	0.121ms
Client - buildApiOptions	427.429ms	136.573ms
Client - buildOperationFiles	28.138s	8.419s
Client - buildClientContext	245.091ms	261.033ms
Client - buildRestorePoller	208.512ms	76.358ms
Client - build api subpath index	1:05.518	20.590s
Client - buildClassicalClient	3.758s	827.024ms
Client - buildClassicOperationFiles	759.447ms	238.931ms
Client - build classic subpath index	20.844s	4.182s
Client - buildRootIndex	34.413s	6.240s
emit source files (per client)	2:34.313	40.972s
emit source files (total)	2:34.313	40.972s
emit samples	1.141s	1.104s
resolve references	22:08.539	3:20.601
generate files	15.296s	6.543s
generate modular sources	30:42.855	4:57.395
Total onEmit	31:25.022	5:17.883
Emitter total reported by TypeSpec CLI	1885023ms	317884ms

Top hotspots (baseline)

Rank	Phase	Network	% of total	Compute	% of total
1	resolve references (binder)	22:08.539	70.5%	3:20.601	63.1%
2	emit models - emitTypes	5:36.832	17.9%	41.720s	13.1%
3	emit source files	2:34.313	8.2%	40.972s	12.9%
4	create context	25.624s	1.4%	13.825s	4.4%
5	generate files	15.296s	0.8%	6.543s	2.1%
6	build models subpath index	6.527s	0.3%	6.411s	2.0%

Within emit source files, the per-client cost is dominated by:

• Network: build api subpath index (1:05), buildRootIndex (34s), buildOperationFiles (28s), build classic subpath index (21s)
• Compute: build api subpath index (21s), buildOperationFiles (8s), buildRootIndex (6s)