Fix decimal numeric with leading zeros (#3898)

fix #3888

.chronus/changes/fix-numeric-leading-zeros-2024-6-18-19-57-12.md

@@ -0,0 +1,8 @@
+---
+# Change versionKind to one of: internal, fix, dependencies, feature, deprecation, breaking
+changeKind: fix
+packages:
+  - "@typespec/compiler"
+---
+
+Fix decimal numeric with leading zeros

packages/compiler/src/core/numeric.ts

@@ -138,8 +138,9 @@ function parse(original: string): InternalData {
 function stringify(value: InternalData) {
   const n = value.n.toString();
   const sign = value.s === -1 ? "-" : "";
-  const decimal = value.e < n.length ? "." + n.slice(value.e) : "";
-  return sign + n.slice(0, value.e) + decimal;
+  const int = value.e === 0 ? "0" : n.slice(0, value.e);
+  const decimal = value.e < n.length ? "." + n.slice(value.e).padStart(value.d, "0") : "";
+  return sign + int + decimal;
 }
 const equals = (a: InternalData, b: InternalData) => a.n === b.n && a.e === b.e;
 

packages/compiler/test/core/numeric.test.ts

@@ -167,6 +167,12 @@ describe("asString", () => {
   it("decimals", () => {
     expect(Numeric("-123.456").toString()).toEqual("-123.456");
   });
+
+  it("decimals with leading 0", () => {
+    expect(Numeric("0.1").toString()).toEqual("0.1");
+    expect(Numeric("0.01").toString()).toEqual("0.01");
+  });
+
   it("data with exponent", () => {
     expect(Numeric("5e6").toString()).toEqual("5000000");
   });
@@ -186,6 +192,8 @@ describe("asNumber", () => {
   it.each([
     ["0", 0],
     ["0.0", 0],
+    ["0.1", 0.1],
+    ["0.01", 0.01],
     ["123", 123],
     ["123.456", 123.456],
     ["123.00", 123],