EC
TS6054
TypeScriptERRORNotableConfigHIGH confidence

File 'X' has an unsupported extension. The only supported extensions are X.

Production Risk

Build will fail; resolve before shipping.

What this means

A compiler configuration error (TS6054): File 'X' has an unsupported extension. The only supported extensions are X.. This diagnostic is emitted by the TypeScript compiler when file 'X' has an unsupported extension. The only supported extensions are X..

Why it happens
  1. 1Incorrect TypeScript syntax or type usage
  2. 2Type mismatch between declared and actual value
How to reproduce

TypeScript compiler reports TS6054 during type checking.

trigger — this will error
trigger — this will error
// Triggers TS6054
// File 'X' has an unsupported extension. The only supported extensions are X.

expected output

error TS6054: File 'X' has an unsupported extension. The only supported extensions are X.

Fix

Fix the tsconfig.json option

WHEN When a compiler option is invalid or missing

Fix the tsconfig.json option
// tsconfig.json
{
  "compilerOptions": {
    // Review and correct the flagged option
  }
}
// Run: npx tsc --showConfig to see effective config

Why this works

TypeScript validates tsconfig.json options; check the official tsconfig reference for valid values.

Sources
Official documentation ↗

TypeScript Compiler Diagnostics

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