[BUG][TYPESCRIPT] Duplicate enum keys cause TS1117 error

Description

hen generating a TypeScript client from an OpenAPI schema containing timezone enums such as "Etc/GMT+12" and "Etc/GMT-12", the generator creates duplicate enum property names (EtcGmt122), leading to a TypeScript compilation error:

src/api/api.ts:12517:5 - error TS1117: An object literal cannot have multiple properties with the same name.

12517     EtcGmt122: 'Etc/GMT-12',
          ~~~~~~~~~

This happens because both "Etc/GMT+12" and "Etc/GMT-12" resolve to the same sanitized identifier (EtcGmt12), and the generator attempts to disambiguate by appending numeric suffixes, which results in collisions again.

openapi-generator version

7.14.0

OpenAPI declaration file content or url

{
  "components": {
    "schemas": {
      "UtcTimezoneEnum": {
        "enum": [
          "Etc/GMT+12",
          "Etc/GMT+11",
          "Etc/GMT+10",
          "Pacific/Marquesas",
          "Etc/GMT+9",
          "Etc/GMT+8",
          "Etc/GMT+7",
          "Etc/GMT+6",
          "Etc/GMT+5",
          "Etc/GMT+4",
          "America/St_Johns",
          "Etc/GMT+3",
          "Etc/GMT+2",
          "Etc/GMT+1",
          "Etc/GMT0",
          "Etc/GMT-1",
          "Europe/Kiev",
          "Etc/GMT-3",
          "Asia/Tehran",
          "Etc/GMT-4",
          "Asia/Kabul",
          "Etc/GMT-5",
          "Asia/Kolkata",
          "Asia/Kathmandu",
          "Etc/GMT-6",
          "Asia/Yangon",
          "Etc/GMT-7",
          "Etc/GMT-8",
          "Australia/Eucla",
          "Etc/GMT-9",
          "Australia/Darwin",
          "Etc/GMT-10",
          "Australia/Lord_Howe",
          "Etc/GMT-11",
          "Etc/GMT-12",
          "Pacific/Chatham",
          "Etc/GMT-13",
          "Etc/GMT-14"
        ],
        "type": "string",
        "description": "* `Etc/GMT+12` - UTC-12:00\n* `Etc/GMT+11` - UTC-11:00\n* `Etc/GMT+10` - UTC-10:00\n* `Pacific/Marquesas` - UTC-09:30\n* `Etc/GMT+9` - UTC-09:00\n* `Etc/GMT+8` - UTC-08:00\n* `Etc/GMT+7` - UTC-07:00\n* `Etc/GMT+6` - UTC-06:00\n* `Etc/GMT+5` - UTC-05:00\n* `Etc/GMT+4` - UTC-04:00\n* `America/St_Johns` - UTC-03:30\n* `Etc/GMT+3` - UTC-03:00\n* `Etc/GMT+2` - UTC-02:00\n* `Etc/GMT+1` - UTC-01:00\n* `Etc/GMT0` - UTC 00:00\n* `Etc/GMT-1` - UTC+01:00\n* `Europe/Kiev` - UTC+02:00\n* `Etc/GMT-3` - UTC+03:00\n* `Asia/Tehran` - UTC+03:30\n* `Etc/GMT-4` - UTC+04:00\n* `Asia/Kabul` - UTC+04:30\n* `Etc/GMT-5` - UTC+05:00\n* `Asia/Kolkata` - UTC+05:30\n* `Asia/Kathmandu` - UTC+05:45\n* `Etc/GMT-6` - UTC+06:00\n* `Asia/Yangon` - UTC+06:30\n* `Etc/GMT-7` - UTC+07:00\n* `Etc/GMT-8` - UTC+08:00\n* `Australia/Eucla` - UTC+08:45\n* `Etc/GMT-9` - UTC+09:00\n* `Australia/Darwin` - UTC+09:30\n* `Etc/GMT-10` - UTC+10:00\n* `Australia/Lord_Howe` - UTC+10:30\n* `Etc/GMT-11` - UTC+11:00\n* `Etc/GMT-12` - UTC+12:00\n* `Pacific/Chatham` - UTC+12:45\n* `Etc/GMT-13` - UTC+13:00\n* `Etc/GMT-14` - UTC+14:00"
      }
    }
  }
}

Generation Details

Generated in api.ts

}
/**
 * * `Etc/GMT+12` - UTC-12:00 * `Etc/GMT+11` - UTC-11:00 * `Etc/GMT+10` - UTC-10:00 * `Pacific/Marquesas` - UTC-09:30 * `Etc/GMT+9` - UTC-09:00 * `Etc/GMT+8` - UTC-08:00 * `Etc/GMT+7` - UTC-07:00 * `Etc/GMT+6` - UTC-06:00 * `Etc/GMT+5` - UTC-05:00 * `Etc/GMT+4` - UTC-04:00 * `America/St_Johns` - UTC-03:30 * `Etc/GMT+3` - UTC-03:00 * `Etc/GMT+2` - UTC-02:00 * `Etc/GMT+1` - UTC-01:00 * `Etc/GMT0` - UTC 00:00 * `Etc/GMT-1` - UTC+01:00 * `Europe/Kiev` - UTC+02:00 * `Etc/GMT-3` - UTC+03:00 * `Asia/Tehran` - UTC+03:30 * `Etc/GMT-4` - UTC+04:00 * `Asia/Kabul` - UTC+04:30 * `Etc/GMT-5` - UTC+05:00 * `Asia/Kolkata` - UTC+05:30 * `Asia/Kathmandu` - UTC+05:45 * `Etc/GMT-6` - UTC+06:00 * `Asia/Yangon` - UTC+06:30 * `Etc/GMT-7` - UTC+07:00 * `Etc/GMT-8` - UTC+08:00 * `Australia/Eucla` - UTC+08:45 * `Etc/GMT-9` - UTC+09:00 * `Australia/Darwin` - UTC+09:30 * `Etc/GMT-10` - UTC+10:00 * `Australia/Lord_Howe` - UTC+10:30 * `Etc/GMT-11` - UTC+11:00 * `Etc/GMT-12` - UTC+12:00 * `Pacific/Chatham` - UTC+12:45 * `Etc/GMT-13` - UTC+13:00 * `Etc/GMT-14` - UTC+14:00
 * @export
 * @enum {string}
 */

export const UtcTimezoneEnum = {
    EtcGmt122: 'Etc/GMT+12',
    EtcGmt11: 'Etc/GMT+11',
    EtcGmt10: 'Etc/GMT+10',
    PacificMarquesas: 'Pacific/Marquesas',
    EtcGmt9: 'Etc/GMT+9',
    EtcGmt8: 'Etc/GMT+8',
    EtcGmt7: 'Etc/GMT+7',
    EtcGmt6: 'Etc/GMT+6',
    EtcGmt5: 'Etc/GMT+5',
    EtcGmt4: 'Etc/GMT+4',
    AmericaStJohns: 'America/St_Johns',
    EtcGmt3: 'Etc/GMT+3',
    EtcGmt2: 'Etc/GMT+2',
    EtcGmt1: 'Etc/GMT+1',
    EtcGmt0: 'Etc/GMT0',
    EtcGmt12: 'Etc/GMT-1',
    EuropeKiev: 'Europe/Kiev',
    EtcGmt32: 'Etc/GMT-3',
    AsiaTehran: 'Asia/Tehran',
    EtcGmt42: 'Etc/GMT-4',
    AsiaKabul: 'Asia/Kabul',
    EtcGmt52: 'Etc/GMT-5',
    AsiaKolkata: 'Asia/Kolkata',
    AsiaKathmandu: 'Asia/Kathmandu',
    EtcGmt62: 'Etc/GMT-6',
    AsiaYangon: 'Asia/Yangon',
    EtcGmt72: 'Etc/GMT-7',
    EtcGmt82: 'Etc/GMT-8',
    AustraliaEucla: 'Australia/Eucla',
    EtcGmt92: 'Etc/GMT-9',
    AustraliaDarwin: 'Australia/Darwin',
    EtcGmt102: 'Etc/GMT-10',
    AustraliaLordHowe: 'Australia/Lord_Howe',
    EtcGmt112: 'Etc/GMT-11',
    EtcGmt122: 'Etc/GMT-12', // <--- duplicate key causes TS1117
    PacificChatham: 'Pacific/Chatham',
    EtcGmt13: 'Etc/GMT-13',
    EtcGmt14: 'Etc/GMT-14'
} as const;

export type UtcTimezoneEnum = typeof UtcTimezoneEnum[keyof typeof UtcTimezoneEnum];

Error:

error TS1117: An object literal cannot have multiple properties with the same name.

Steps to reproduce

npx openapi-generator-cli generate -g typescript-axios -i http://localhost:8000/api/schema/?format=json -o ./src/api/

Suggest a fix

In the TypeScript enum generator, enhance the logic to include sign indicators for numeric parts when generating identifiers from enum values.
For example:

• "Etc/GMT+12" → EtcGmtPos12
• "Etc/GMT-12" → EtcGmtNeg12

This ensures stable and unique keys without violating TypeScript syntax rules.

Start with the TypeScript enum generation logic used by the typescript-axios generator and reproduce the issue with the provided OpenAPI schema. Check how sanitized enum names and numeric suffixes are produced; done means the generated api.ts has unique valid keys for both signed GMT values and compiles without TS1117.