Tracing module resolution
As discussed earlier, the compiler can visit files outside the current folder when resolving a module. This can be hard when diagnosing why a module is not resolved, or is resolved to an incorrect definition. Enabling the compiler module resolution tracing using --traceResolution provides insight in what happened during the module resolution process.
Let’s say we have a sample application that uses the typescript module. app.ts has an import like import * as ts from "typescript".
│ tsconfig.json
├───node_modules
│ └───typescript
│ └───lib
│ typescript.d.ts
└───src
app.ts
Invoking the compiler with --traceResolution
tsc --traceResolution
Results in an output as such:
======== Resolving module 'typescript' from 'src/app.ts'. ======== Module resolution kind is not specified, using 'NodeJs'. Loading module 'typescript' from 'node_modules' folder. File 'src/node_modules/typescript.ts' does not exist. File 'src/node_modules/typescript.tsx' does not exist. File 'src/node_modules/typescript.d.ts' does not exist. File 'src/node_modules/typescript/package.json' does not exist. File 'node_modules/typescript.ts' does not exist. File 'node_modules/typescript.tsx' does not exist. File 'node_modules/typescript.d.ts' does not exist. Found 'package.json' at 'node_modules/typescript/package.json'. 'package.json' has 'typings' field './lib/typescript.d.ts' that references 'node_modules/typescript/lib/typescript.d.ts'. File 'node_modules/typescript/lib/typescript.d.ts' exist - use it as a module resolution result. ======== Module name 'typescript' was successfully resolved to 'node_modules/typescript/lib/typescript.d.ts'. ========
Things to look out for
- Name and location of the import
======== Resolving module ‘typescript’ from ‘src/app.ts’. ========
- The strategy the compiler is following
Module resolution kind is not specified, using ‘NodeJs’.
- Loading of typings from npm packages
‘package.json’ has ‘typings’ field ‘./lib/typescript.d.ts’ that references ‘node_modules/typescript/lib/typescript.d.ts’.
- Final result
======== Module name ‘typescript’ was successfully resolved to ‘node_modules/typescript/lib/typescript.d.ts’. ========
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