Possible Bug

Repo example for issue #8419.

As stated in the issue, it happens that the contenthash changes while the file content stay fixed between builds. Here below is the result of running several times consecutively until get the error, 7 buids in around 20 seconds without any change to the source code shows the file changing from trial.main.7373d414d17dcd91e77f.js to trial.main.90f6742c6e777575c140.js. Notice that the number of runs to find the error is kind of random, might be 2 or 3 like more than 10.

I reduced to what it seems to be the simplest case to reproduce it, where it contains a package in node_modules (simulated with a "utils": "file:./utils") while if the content is inside a folder in src, I can not reproduce the error.

Note 1: I tried also with a JS version of the same example, and I can not reproduce the error. Then, I guess it is related somehow to ts-loader.

Note 2: I have compared the files generated with several tools (e.g., diff, cmp, stat, checksum, BOM existence) finding no difference at all. I stored these 2 files in the example folder, for further investigation.

How to reproduce

# to install the depedencies
yarn

# execute several times until see a different `contenthash`
yarn build

Note 3: There is no cleanup between builds, the results are collected in tmp folder.

Execution results

~/webpack-bug >$ yarn build
yarn run v1.17.3
$ webpack --mode=production
Hash: cee9fd2c2419387e124e
Version: webpack 4.41.1
Time: 1139ms
Built at: 10/14/2019 10:29:23 PM
                             Asset      Size  Chunks                         Chunk Names
trial.main.7373d414d17dcd91e77f.js  1.16 KiB       0  [emitted] [immutable]  trial
Entrypoint trial = trial.main.7373d414d17dcd91e77f.js
[0] multi ./src/foo.ts ./src/bar.ts 40 bytes {0} [built]
[UO9Q] ./src/foo.ts + 2 modules 227 bytes {0} [built]
    | ./src/foo.ts 29 bytes [built]
    |     + 2 hidden modules
[j5Z2] ./src/bar.ts 23 bytes {0} [built]
✨  Done in 2.10s.

~/webpack-bug >$ yarn build
yarn run v1.17.3
$ webpack --mode=production
Hash: cee9fd2c2419387e124e
Version: webpack 4.41.1
Time: 1124ms
Built at: 10/14/2019 10:29:27 PM
                             Asset      Size  Chunks                         Chunk Names
trial.main.7373d414d17dcd91e77f.js  1.16 KiB       0  [emitted] [immutable]  trial
Entrypoint trial = trial.main.7373d414d17dcd91e77f.js
[0] multi ./src/foo.ts ./src/bar.ts 40 bytes {0} [built]
[UO9Q] ./src/foo.ts + 2 modules 227 bytes {0} [built]
    | ./src/foo.ts 29 bytes [built]
    |     + 2 hidden modules
[j5Z2] ./src/bar.ts 23 bytes {0} [built]
✨  Done in 2.10s.

~/webpack-bug >$ yarn build
yarn run v1.17.3
$ webpack --mode=production
Hash: cee9fd2c2419387e124e
Version: webpack 4.41.1
Time: 1142ms
Built at: 10/14/2019 10:29:29 PM
                             Asset      Size  Chunks                         Chunk Names
trial.main.7373d414d17dcd91e77f.js  1.16 KiB       0  [emitted] [immutable]  trial
Entrypoint trial = trial.main.7373d414d17dcd91e77f.js
[0] multi ./src/foo.ts ./src/bar.ts 40 bytes {0} [built]
[UO9Q] ./src/foo.ts + 2 modules 227 bytes {0} [built]
    | ./src/foo.ts 29 bytes [built]
    |     + 2 hidden modules
[j5Z2] ./src/bar.ts 23 bytes {0} [built]
✨  Done in 2.10s.

~/webpack-bug >$ yarn build
yarn run v1.17.3
$ webpack --mode=production
Hash: cee9fd2c2419387e124e
Version: webpack 4.41.1
Time: 1403ms
Built at: 10/14/2019 10:29:33 PM
                             Asset      Size  Chunks                         Chunk Names
trial.main.7373d414d17dcd91e77f.js  1.16 KiB       0  [emitted] [immutable]  trial
Entrypoint trial = trial.main.7373d414d17dcd91e77f.js
[0] multi ./src/foo.ts ./src/bar.ts 40 bytes {0} [built]
[UO9Q] ./src/foo.ts + 2 modules 227 bytes {0} [built]
    | ./src/foo.ts 29 bytes [built]
    |     + 2 hidden modules
[j5Z2] ./src/bar.ts 23 bytes {0} [built]
✨  Done in 2.40s.

~/webpack-bug >$ yarn build
yarn run v1.17.3
$ webpack --mode=production
Hash: cee9fd2c2419387e124e
Version: webpack 4.41.1
Time: 1149ms
Built at: 10/14/2019 10:29:37 PM
                             Asset      Size  Chunks                         Chunk Names
trial.main.7373d414d17dcd91e77f.js  1.16 KiB       0  [emitted] [immutable]  trial
Entrypoint trial = trial.main.7373d414d17dcd91e77f.js
[0] multi ./src/foo.ts ./src/bar.ts 40 bytes {0} [built]
[UO9Q] ./src/foo.ts + 2 modules 227 bytes {0} [built]
    | ./src/foo.ts 29 bytes [built]
    |     + 2 hidden modules
[j5Z2] ./src/bar.ts 23 bytes {0} [built]
✨  Done in 2.50s.

~/webpack-bug >$ yarn build
yarn run v1.17.3
$ webpack --mode=production
Hash: cee9fd2c2419387e124e
Version: webpack 4.41.1
Time: 1159ms
Built at: 10/14/2019 10:29:40 PM
                             Asset      Size  Chunks                         Chunk Names
trial.main.7373d414d17dcd91e77f.js  1.16 KiB       0  [emitted] [immutable]  trial
Entrypoint trial = trial.main.7373d414d17dcd91e77f.js
[0] multi ./src/foo.ts ./src/bar.ts 40 bytes {0} [built]
[UO9Q] ./src/foo.ts + 2 modules 227 bytes {0} [built]
    | ./src/foo.ts 29 bytes [built]
    |     + 2 hidden modules
[j5Z2] ./src/bar.ts 23 bytes {0} [built]
✨  Done in 2.13s.

~/webpack-bug >$ yarn build
yarn run v1.17.3
$ webpack --mode=production
Hash: 700d95a36a172d8b1fed
Version: webpack 4.41.1
Time: 1134ms
Built at: 10/14/2019 10:29:42 PM
                             Asset      Size  Chunks                         Chunk Names
trial.main.90f6742c6e777575c140.js  1.16 KiB       0  [emitted] [immutable]  trial
Entrypoint trial = trial.main.90f6742c6e777575c140.js
[0] multi ./src/foo.ts ./src/bar.ts 40 bytes {0} [built]
[UO9Q] ./src/foo.ts + 2 modules 227 bytes {0} [built]
    | ./src/foo.ts 29 bytes [built]
    |     + 2 hidden modules
[j5Z2] ./src/bar.ts 23 bytes {0} [built]
✨  Done in 2.10s.