I have the following Dockerfile which is failing at the step which compiles TypeScript:

FROM node:12
WORKDIR /usr/src/app

# SETUP

COPY package.json .
COPY tsconfig.json .
COPY src .

RUN npm install -g yarn@^1.16.0
RUN yarn install

# BUILD

RUN npx tsc <------------------------

The error message is very confusing:

File '/usr/src/app/app.ts' is not under 'rootDir' '/usr/src/app/src'. 'rootDir' is expected to contain all source files.

This makes no sense... It's finding app.ts under the src folder and then complaining that it isn't under the src folder.

Files:

src
  app.ts
tsconfig.json
Dockerfile

How do I solve this issue?

Here is my tsconfig.json:

{
  "compilerOptions": {
    ...
    "rootDir": "./src",
    "outDir": "./build",
    ...
  }
}