TypeError: mappedCoverage.addStatement is not a function

• Issue

I updated my project to Jest 20.0.1 and updated ts-jest to 20.0.3 as well. I tried out the new coverage feature and get following error:

UnhandledPromiseRejectionWarning: Unhandled promise rejection (rejection id: 2): TypeError: mappedCoverage.addStatement is not a function

• Expected behavior

Coverage should run.

• my config

"jest": {
    "globals": {
      "__TS_CONFIG__": "./test/tsconfig.json"
    },
    "transform": {
      ".(ts|tsx)": "<rootDir>/node_modules/ts-jest/preprocessor.js"
    },
    "testRegex": "(/__tests__/.*|\\.(test|spec))\\.(ts|tsx|js)$",
    "testPathIgnorePatterns": [
      "<rootDir>/build"
    ],
    "snapshotSerializers": [
      "enzyme-to-json/serializer"
    ],
    "setupTestFrameworkScriptFile": "./test/setupTestFramework.ts",
    "mapCoverage": true,
    "moduleFileExtensions": [
      "ts",
      "tsx",
      "js"
    ],
    "moduleNameMapper": {
      "\\.(svg|woff|ttf|eot)$": "<rootDir>/test/__mocks__/fileMock.js",
      "\\.(css)$": "<rootDir>/test/__mocks__/styleMock.js"
    },
    "setupFiles": [
      "./test/setupJest.ts"
    ]
  },

[jrwebdev]

I’ve had another look into this - the issue (at least with my config) is when allowSyntheticDefaultImports is set to true. If set, the preprocessor runs files through babel-jest and appends a .js extension onto them. When the coverage is generated, both the .ts / .tsx and .ts.js / .tsx.js files are run through the coverage generator, but source maps are only found for .ts.js / .tsx.js files, so the original files encounter the problems I described above with missing source maps.

I’m afraid this is about as far as I can take it in terms of a fix, but I hope the above info is helpful to whoever picks this up.

[jrwebdev]

I had this issue at work last week, but being relatively new to TypeScript I assumed it was some form of configuration I’d set incorrectly. I didn’t find the problem, but I traced it down to istanbul-lib-source-maps - it appears that it’s unable to find a source map, so it just uses a file coverage object for the given file:

https://github.com/istanbuljs/istanbuljs/blob/master/packages/istanbul-lib-source-maps/lib/transformer.js#L161

Then due to this it doesn’t instantiate MappedCoverage:

https://github.com/istanbuljs/istanbuljs/blob/master/packages/istanbul-lib-source-maps/lib/transformer.js#L152

This is when I assumed I’d screwed up generating source maps and went back to experimenting with that, but didn’t get any further before I left for the weekend. Only thing I really tried doing was using inlineSourceMap instead of sourceMap.

The only other bits of info I can give at the moment that may help is that I’m also pretty sure if I put in a check for addStatement being available before it is called (along with addFunction and addBranch which also are missing), it did go ahead and generate everything successfully as far as I could see. I also had it working on a branch that just contained a couple of tests for very basic functions in .ts files, but when .tsx files and Enzyme were threw into the mix as well that’s when the issues started.