Support configurable casing styles in Azure Core

[Timothee Guerin (timotheeguerin)]

Services with existing snake_case APIs, such as Foundry, currently have to disable Azure Core's casing-style rule instead of using it to enforce their own conventions. This also prevents shared libraries from packaging an appropriate naming policy in their rulesets.

Allow casing to be configured per declaration category, so a service can require snake_case properties and members while retaining the usual type and operation naming:

linter:
  enable:
    "@azure-tools/typespec-azure-core/casing-style":
      modelProperty: snake_case
      unionVariant: snake_case
      enumMember: snake_case

Each category accepts camelCase, PascalCase, snake_case, or false. Existing defaults and diagnostics are unchanged; additional checks for unions, enums, scalars, and their applicable members are opt-in. Options are schema-validated and can be supplied by a library ruleset or overridden in a service's configuration.

[github-actions]

All changed packages have been documented.

• ✅ @azure-tools/typespec-azure-core

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@azure-tools/typespec-azure-core - feature ✏️

Configure casing-style per declaration category, including opt-in snake_case properties,,> operation parameters, union variants, and enum members. Existing Azure defaults remain unchanged.,> ,> yaml,> linter:,> enable:,> "@azure-tools/typespec-azure-core/casing-style":,> modelProperty: snake_case,> union: PascalCase,> unionVariant: snake_case,> enum: PascalCase,> enumMember: snake_case,> scalar: PascalCase,>

[github-actions]

📦 Package size report

1 package changed size, +1.07 KB (+0.0%) packed overall.

Package	Packed (base → head)	Δ Packed	Unpacked (base → head)	Δ Unpacked
@azure-tools/typespec-azure-core	133.12 KB → 134.19 KB	+1.07 KB (+0.8%) 🔴	721.70 KB → 724.18 KB	+2.48 KB (+0.3%)

12 package(s) with no notable change

Package	Packed (base → head)	Δ Packed	Unpacked (base → head)	Δ Unpacked
@azure-tools/typespec-ts	540.84 KB → 540.83 KB	-8 B (-0.0%)	2.60 MB → 2.60 MB	-149 B (-0.0%)
@azure-tools/azure-http-specs	148.36 KB → 148.36 KB	—	1.17 MB → 1.17 MB	—
@azure-tools/typespec-autorest	81.98 KB → 81.98 KB	—	400.59 KB → 400.59 KB	—
@azure-tools/typespec-autorest-canonical	7.42 KB → 7.42 KB	—	26.00 KB → 26.00 KB	—
@azure-tools/typespec-azure-portal-core	42.48 KB → 42.48 KB	—	193.20 KB → 193.20 KB	—
@azure-tools/typespec-azure-resource-manager	184.05 KB → 184.05 KB	—	1.11 MB → 1.11 MB	—
@azure-tools/typespec-azure-rulesets	5.50 KB → 5.50 KB	—	33.67 KB → 33.67 KB	—
@azure-tools/typespec-client-generator-core	240.28 KB → 240.28 KB	—	1.28 MB → 1.28 MB	—
@azure-tools/typespec-go	263.56 KB → 263.56 KB	—	1.35 MB → 1.35 MB	—
@azure-tools/typespec-java	13.51 MB → 13.51 MB	—	15.04 MB → 15.04 MB	—
@azure-tools/typespec-metadata	15.91 KB → 15.91 KB	—	62.26 KB → 62.26 KB	—
@azure-tools/typespec-python	42.22 KB → 42.22 KB	—	164.91 KB → 164.91 KB	—

_{Packed = gzipped .tgz published to npm. Unpacked = total extracted size. 🆕 added, 🗑️ removed. Packages from the core/ submodule are not included.
🔴 grew · 🟢 shrank — only changes of at least 512 B and 0.5% are marked.}

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npm i https://pkg.pr.new/@azure-tools/typespec-azure-core@5602

commit: 1550030

[azure-sdk-automation]

You can try these changes here

🛝 Playground	🌐 Website

[catalinaperalta]

lgtm, just one doc improvement