Add no-generic-numeric rule to disable LintDiff `IntegerTypeMustHav…

…eFormat` (#619)

Closes #669.

**REST API Specs**
Azure/azure-rest-api-specs#28731

.chronus/changes/core-IntegerTypesRule-2024-3-10-16-52-31.md

@@ -0,0 +1,8 @@
+---
+# Change versionKind to one of: internal, fix, dependencies, feature, deprecation, breaking
+changeKind: fix
+packages:
+  - "@azure-tools/typespec-azure-core"
+---
+
+Add `no-generic-numeric` rule to disable LintDiff `IntegerTypeMustHaveFormat`

docs/libraries/azure-core/reference/linter.md

@@ -42,6 +42,7 @@ Available ruleSets:
 | `@azure-tools/typespec-azure-core/no-explicit-routes-resource-ops`                                                   | The @route decorator should not be used on standard resource operation signatures.                                                                   |
 | `@azure-tools/typespec-azure-core/no-fixed-enum-discriminator`                                                       | Discriminator shouldn't be a fixed enum.                                                                                                             |
 | [`@azure-tools/typespec-azure-core/non-breaking-versioning`](/libraries/azure-core/rules/non-breaking-versioning.md) | Check that only backward compatible versioning change are done to a service.                                                                         |
+| [`@azure-tools/typespec-azure-core/no-generic-numeric`](/libraries/azure-core/rules/no-generic-numeric.md)           | Don't use generic types. Use more specific types instead.                                                                                            |
 | `@azure-tools/typespec-azure-core/no-nullable`                                                                       | Use `?` for optional properties.                                                                                                                     |
 | `@azure-tools/typespec-azure-core/no-offsetdatetime`                                                                 | Prefer using `utcDateTime` when representing a datetime unless an offset is necessary.                                                               |
 | `@azure-tools/typespec-azure-core/no-response-body`                                                                  | Ensure that the body is set correctly for the response type.                                                                                         |

docs/libraries/azure-core/rules/no-generic-numeric.md

@@ -0,0 +1,47 @@
+---
+title: "no-generic-numeric"
+---
+
+```text title="Full name"
+@azure-tools/typespec-azure-core/no-generic-numeric
+```
+
+Azure services should use numeric types that specify the bit-width instead of generic types.
+
+#### ❌ Incorrect
+
+```tsp
+model Widget {
+  id: integer;
+  cost: float;
+}
+```
+
+#### ✅ Correct
+
+```tsp
+model Widget {
+  id: safeint;
+  cost: float32;
+}
+```
+
+This includes extending generic numeric types.
+
+#### ❌ Incorrect
+
+```tsp
+model GenericInteger extends integer;
+
+model Widget {
+  id: GenericInteger;
+}
+```
+
+#### ✅ Correct
+
+```tsp
+model Widget {
+  id: safeint;
+}
+```

packages/typespec-azure-core/README.md

@@ -46,6 +46,7 @@ Available ruleSets:
 | `@azure-tools/typespec-azure-core/no-explicit-routes-resource-ops`                                                                                           | The @route decorator should not be used on standard resource operation signatures.                                                                   |
 | `@azure-tools/typespec-azure-core/no-fixed-enum-discriminator`                                                                                               | Discriminator shouldn't be a fixed enum.                                                                                                             |
 | [`@azure-tools/typespec-azure-core/non-breaking-versioning`](https://azure.github.io/typespec-azure/docs/libraries/azure-core/rules/non-breaking-versioning) | Check that only backward compatible versioning change are done to a service.                                                                         |
+| [`@azure-tools/typespec-azure-core/no-generic-numeric`](https://azure.github.io/typespec-azure/docs/libraries/azure-core/rules/no-generic-numeric)           | Don't use generic types. Use more specific types instead.                                                                                            |
 | `@azure-tools/typespec-azure-core/no-nullable`                                                                                                               | Use `?` for optional properties.                                                                                                                     |
 | `@azure-tools/typespec-azure-core/no-offsetdatetime`                                                                                                         | Prefer using `utcDateTime` when representing a datetime unless an offset is necessary.                                                               |
 | `@azure-tools/typespec-azure-core/no-response-body`                                                                                                          | Ensure that the body is set correctly for the response type.                                                                                         |

packages/typespec-azure-core/src/linter.ts

@@ -13,6 +13,7 @@ import { noEnumRule } from "./rules/no-enum.js";
 import { noErrorStatusCodesRule } from "./rules/no-error-status-codes.js";
 import { noExplicitRoutesResourceOps } from "./rules/no-explicit-routes-resource-ops.js";
 import { noFixedEnumDiscriminatorRule } from "./rules/no-fixed-enum-discriminator.js";
+import { noGenericNumericRule } from "./rules/no-generic-numeric.js";
 import { noNullableRule } from "./rules/no-nullable.js";
 import { noOffsetDateTimeRule } from "./rules/no-offsetdatetime.js";
 import { operationIdRule } from "./rules/no-operation-id.js";
@@ -51,6 +52,7 @@ const rules = [
   noExplicitRoutesResourceOps,
   noFixedEnumDiscriminatorRule,
   nonBreakingVersioningRule,
+  noGenericNumericRule,
   noNullableRule,
   noOffsetDateTimeRule,
   noResponseBodyRule,

packages/typespec-azure-core/src/rules/no-generic-numeric.ts

@@ -0,0 +1,64 @@
+import { Model, Scalar, createRule, paramMessage } from "@typespec/compiler";
+
+const disallowList = new Set(["integer", "numeric", "float", "decimal"]);
+const alternatives = new Map([
+  ["integer", "int32"],
+  ["numeric", "int32"],
+  ["float", "float32"],
+  ["decimal", "float32"],
+]);
+
+export const noGenericNumericRule = createRule({
+  name: "no-generic-numeric",
+  description: "Don't use generic types. Use more specific types instead.",
+  severity: "warning",
+  url: "https://azure.github.io/typespec-azure/docs/libraries/azure-core/rules/no-generic-numeric",
+  messages: {
+    default: paramMessage`Don't use generic type '${"name"}'. Use a more specific type that specifies the bit size, such as '${"alternative"}' instead.`,
+    extend: paramMessage`Don't extend generic type '${"name"}'. Use a more specific type that specifies the bit size, such as '${"alternative"}' instead.`,
+  },
+  create(context) {
+    return {
+      model: (model: Model) => {
+        for (const [_, prop] of model.properties) {
+          if (prop.type.kind === "Scalar") {
+            if (disallowList.has(prop.type.name)) {
+              context.reportDiagnostic({
+                target: prop,
+                format: {
+                  name: prop.type.name,
+                  alternative: alternatives.get(prop.type.name)!,
+                },
+              });
+            }
+          }
+        }
+      },
+      scalar: (scalar: Scalar) => {
+        // if the scalar is the base scalar, then we don't need to check it as it will surface
+        // in usage (for example: as a model property)
+        if (disallowList.has(scalar.name)) {
+          return;
+        }
+        let baseScalar: Scalar | undefined = undefined;
+        while (scalar.baseScalar !== undefined) {
+          baseScalar = scalar.baseScalar;
+          break;
+        }
+        if (baseScalar === undefined) {
+          return;
+        }
+        if (disallowList.has(baseScalar.name)) {
+          context.reportDiagnostic({
+            target: scalar,
+            messageId: "extend",
+            format: {
+              name: baseScalar.name,
+              alternative: alternatives.get(baseScalar.name)!,
+            },
+          });
+        }
+      },
+    };
+  },
+});

packages/typespec-azure-core/test/rules/no-generic-numeric.test.ts

@@ -0,0 +1,97 @@
+import {
+  BasicTestRunner,
+  LinterRuleTester,
+  createLinterRuleTester,
+} from "@typespec/compiler/testing";
+import { beforeEach, it } from "vitest";
+import { noGenericNumericRule } from "../../src/rules/no-generic-numeric.js";
+import { createAzureCoreTestRunner } from "../test-host.js";
+
+let runner: BasicTestRunner;
+let tester: LinterRuleTester;
+
+beforeEach(async () => {
+  runner = await createAzureCoreTestRunner({ omitServiceNamespace: true });
+  tester = createLinterRuleTester(runner, noGenericNumericRule, "@azure-tools/typespec-azure-core");
+});
+
+it("emits a warning for generic numeric types", async () => {
+  await tester
+    .expect(
+      `
+      namespace Azure.Widget;
+
+      model Widget {
+        prop1: integer;
+        prop2: numeric;
+        prop3: float;
+        prop4: decimal;
+      }
+      `
+    )
+    .toEmitDiagnostics([
+      {
+        code: "@azure-tools/typespec-azure-core/no-generic-numeric",
+        message:
+          "Don't use generic type 'integer'. Use a more specific type that specifies the bit size, such as 'int32' instead.",
+      },
+      {
+        code: "@azure-tools/typespec-azure-core/no-generic-numeric",
+        message:
+          "Don't use generic type 'numeric'. Use a more specific type that specifies the bit size, such as 'int32' instead.",
+      },
+      {
+        code: "@azure-tools/typespec-azure-core/no-generic-numeric",
+        message:
+          "Don't use generic type 'float'. Use a more specific type that specifies the bit size, such as 'float32' instead.",
+      },
+      {
+        code: "@azure-tools/typespec-azure-core/no-generic-numeric",
+        message:
+          "Don't use generic type 'decimal'. Use a more specific type that specifies the bit size, such as 'float32' instead.",
+      },
+    ]);
+});
+
+it("emits a warning when extending generic numeric types", async () => {
+  await tester
+    .expect(
+      `
+      namespace Azure.Widget;
+
+      scalar GenericInteger extends integer;
+      scalar GenericNumeric extends numeric;
+      scalar GenericFloat extends float;
+      scalar GenericDecimal extends decimal;
+      
+      model Widget {
+        prop1: GenericInteger;
+        prop2: GenericNumeric;
+        prop3: GenericFloat;
+        prop4: GenericDecimal;
+      }
+      `
+    )
+    .toEmitDiagnostics([
+      {
+        code: "@azure-tools/typespec-azure-core/no-generic-numeric",
+        message:
+          "Don't extend generic type 'integer'. Use a more specific type that specifies the bit size, such as 'int32' instead.",
+      },
+      {
+        code: "@azure-tools/typespec-azure-core/no-generic-numeric",
+        message:
+          "Don't extend generic type 'numeric'. Use a more specific type that specifies the bit size, such as 'int32' instead.",
+      },
+      {
+        code: "@azure-tools/typespec-azure-core/no-generic-numeric",
+        message:
+          "Don't extend generic type 'float'. Use a more specific type that specifies the bit size, such as 'float32' instead.",
+      },
+      {
+        code: "@azure-tools/typespec-azure-core/no-generic-numeric",
+        message:
+          "Don't extend generic type 'decimal'. Use a more specific type that specifies the bit size, such as 'float32' instead.",
+      },
+    ]);
+});