This repo exists to demonstrate an odd issue with ts-loader

Module versions

• ts-loader: 2.3.7
• typescript: 2.5.3
• webpack: 3.7.1

This is an issue on a very large (Angular 2) codebase we have, and is preventing us from getting faster builds with ts-loader.

I've managed to get the repro down to 2 files, both under 10 lines.

Repro

• Clone this repo
• npm install
• Run webpack: webpack --verbose

e.g.

$ webpack --verbose
ts-loader: Using typescript@2.5.3 and /tmp/tsltest/src/tsconfig.json
Hash: 393ff3de3d58f1e0d47c
Version: webpack 3.7.1
Time: 710ms
    Asset     Size  Chunks             Chunk Names
bundle.js  4.21 kB       0  [emitted]  bundle
Entrypoint bundle = bundle.js
chunk    {0} bundle.js (bundle) 1.26 kB [entry] [rendered]
    > bundle [0] ./src/e1.ts 
    [0] ./src/e1.ts 1.15 kB {0} [depth 0] [built]
        [exports: AClass]
    [1] ./src/f1.ts 114 bytes {0} [depth 1] [built]
        [exports: AnEnum]
        [only some exports used: AnInterface]
        harmony import ./f1 [0] ./src/e1.ts 10:0-35

WARNING in ./src/e1.ts
17:61-72 "export 'AnInterface' was not found in './f1'
    at HarmonyImportSpecifierDependency._getErrors (/tmp/tsltest/node_modules/webpack/lib/dependencies/HarmonyImportSpecifierDependency.js:65:15)
    at HarmonyImportSpecifierDependency.getWarnings (/tmp/tsltest/node_modules/webpack/lib/dependencies/HarmonyImportSpecifierDependency.js:39:15)
    at Compilation.reportDependencyErrorsAndWarnings (/tmp/tsltest/node_modules/webpack/lib/Compilation.js:701:24)
    at Compilation.finish (/tmp/tsltest/node_modules/webpack/lib/Compilation.js:559:9)
    at applyPluginsParallel.err (/tmp/tsltest/node_modules/webpack/lib/Compiler.js:506:17)
    at /tmp/tsltest/node_modules/tapable/lib/Tapable.js:289:11
    at _addModuleChain (/tmp/tsltest/node_modules/webpack/lib/Compilation.js:505:11)
    at processModuleDependencies.err (/tmp/tsltest/node_modules/webpack/lib/Compilation.js:475:14)
    at _combinedTickCallback (internal/process/next_tick.js:67:7)
    at process._tickCallback (internal/process/next_tick.js:98:9)

WARNING in ./src/e1.ts
17:92-103 "export 'AnInterface' was not found in './f1'
    at HarmonyImportSpecifierDependency._getErrors (/tmp/tsltest/node_modules/webpack/lib/dependencies/HarmonyImportSpecifierDependency.js:65:15)
    at HarmonyImportSpecifierDependency.getWarnings (/tmp/tsltest/node_modules/webpack/lib/dependencies/HarmonyImportSpecifierDependency.js:39:15)
    at Compilation.reportDependencyErrorsAndWarnings (/tmp/tsltest/node_modules/webpack/lib/Compilation.js:701:24)
    at Compilation.finish (/tmp/tsltest/node_modules/webpack/lib/Compilation.js:559:9)
    at applyPluginsParallel.err (/tmp/tsltest/node_modules/webpack/lib/Compiler.js:506:17)
    at /tmp/tsltest/node_modules/tapable/lib/Tapable.js:289:11
    at _addModuleChain (/tmp/tsltest/node_modules/webpack/lib/Compilation.js:505:11)
    at processModuleDependencies.err (/tmp/tsltest/node_modules/webpack/lib/Compilation.js:475:14)
    at _combinedTickCallback (internal/process/next_tick.js:67:7)
    at process._tickCallback (internal/process/next_tick.js:98:9)

It looks like the harmony importer is failing to find an import which is actually an interface.

Minimal Repro Details

I've managed to reduce this down from the many thousands of files in our codebase. It seems to require a combination of all of the following:

• ts-loader transpileOnly set to true
• Import of an interface (or a TS type) - something that is only type information
• Export of something concrete from the module exporting the interface
• The imported interface being used in a decorated class (with tsconfig emitDecoratorMetadata set to true)