Crash when `package.json` uses wrong type of value for `typings`, `types`, or `main` fields

[juanmait]

TypeScript Version: 3.7.2

Search Terms:

• charCodeAt
• path.charCodeAt is not a function TSINTERNAL_ERROR
• getDirectoryOrExtensionlessFileName
• getEncodedRootLength

Code

TypeScript/src/compiler/moduleSpecifiers.ts

Line 337 in 7c14aff

const mainFileRelative = packageJsonContent.typings || packageJsonContent.types || packageJsonContent.main;

Expected behavior:
To handle cases in which mainFileRelative resolves to other than a string.

Actual behavior:
Crashes and unexpected bugs under some conditions when mainFileRelative resolves to for example an array. The result is then handled by getEncodedRootLength at:

TypeScript/src/compiler/path.ts

Line 117 in 7c14aff

function getEncodedRootLength(path: string): number {

Which end up calling charCodeAt in something that is not a string:

TypeScript/src/compiler/path.ts

Line 119 in 7c14aff

const ch0 = path.charCodeAt(0);

Failed to compile.

[internal]
TypeScript error in [internal](undefined,undefined):
path.charCodeAt is not a function  TSINTERNAL_ERROR

at: getDirectoryOrExtensionlessFileName
path: /***/***/ts-weird-bug/node_modules/csv-parse/lib/index.d.ts
content of types field: [ "./lib/index.d.ts", "./lib/sync.d.ts" ]

at: getEncodedRootLength

TypeError: path.charCodeAt is not a function
    at getEncodedRootLength (/***/***/ts-weird-bug/node_modules/typescript/lib/typescript.js:5830:27)
    at isRootedDiskPath (/***/***/ts-weird-bug/node_modules/typescript/lib/typescript.js:5742:16)
    at Object.toPath (/***/***/ts-weird-bug/node_modules/typescript/lib/typescript.js:6163:36)
    at getDirectoryOrExtensionlessFileName (/***/***/ts-weird-bug/node_modules/typescript/lib/typescript.js:99655:49)
    at tryGetModuleNameAsNodeModule (/***/***/ts-weird-bug/node_modules/typescript/lib/typescript.js:99631:70)
    at /***/***/ts-weird-bug/node_modules/typescript/lib/typescript.js:99451:88
    at Object.mapDefined (/***/***/ts-weird-bug/node_modules/typescript/lib/typescript.js:704:30)
    at Object.getModuleSpecifiers (/***/***/ts-weird-bug/node_modules/typescript/lib/typescript.js:99451:29)
    at getSpecifierForModuleSymbol (/***/***/ts-weird-bug/node_modules/typescript/lib/typescript.js:37232:62)
    at /***/***/ts-weird-bug/node_modules/typescript/lib/typescript.js:37098:39

Playground Link:

A repo that reproduces the issue: https://github.com/juanmait/ts-weird-bug. All the details are in the readme. Unfortunately the issue happen due to a combination of factors. A third party library that ships an invalid value for the field types in the package.json, some trickery made by react-scripts and this typescript bug (?

Related Issues:

#16048

[reduardo7]

Why in the Backlog? It is a blocker issue. :-/