EC
TS5109
TypeScriptERRORNotableConfigHIGH confidence

Option 'moduleResolution' must be set to 'X' (or left unspecified) when optio...

Production Risk

Build will fail; resolve before shipping.

What this means

A compiler configuration error (TS5109): Option 'moduleResolution' must be set to 'X' (or left unspecified) when option 'module' is set to 'X'.. This diagnostic is emitted by the TypeScript compiler when option 'moduleResolution' must be set to 'X' (or left unspecified) when option 'module' is set to '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 TS5109 during type checking.

trigger — this will error
trigger — this will error
// Triggers TS5109
// Option 'moduleResolution' must be set to 'X' (or left unspecified) when option 'module' is set to 'X'.

expected output

error TS5109: Option 'moduleResolution' must be set to 'X' (or left unspecified) when option 'module' is set to '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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