Allow options.configFile to be undefined

[mjbvz]

Expected Behaviour

options.configFile should allow passing in undefined to fallback the standard config file

We hit this with a webpack config generator function that looks like:

function createWebpackConfig(configFileName: string | undefined) {
 ...
}

Sometimes we want to override the config file but usually we do not

Actual Behaviour

Passing in undefined produces the following build error:

Module build failed (from ./node_modules/ts-loader/index.js):
TypeError [ERR_INVALID_ARG_TYPE]: The "path" argument must be of type string. Received undefined
    at validateString (internal/validators.js:124:11)
    at Object.isAbsolute (path.js:1133:5)
    at findConfigFile (/workspaces/ts-loader/examples/vanilla/node_modules/ts-loader/dist/config.js:57:14)
    at Object.getConfigFile (/workspaces/ts-loader/examples/vanilla/node_modules/ts-loader/dist/config.js:8:28)
    at successfulTypeScriptInstance (/workspaces/ts-loader/examples/vanilla/node_modules/ts-loader/dist/instances.js:74:40)
    at Object.getTypeScriptInstance (/workspaces/ts-loader/examples/vanilla/node_modules/ts-loader/dist/instances.js:42:12)
    at Object.loader (/workspaces/ts-loader/examples/vanilla/node_modules/ts-loader/dist/index.js:16:41)

Again, I'd expect undefined to be treated as if the configFile property has been omitted entirely

Steps to Reproduce the Problem

1. In examples/vanilla, update the rules to:

rules: [
    {
        test: /\.tsx?$/,
        loader: 'ts-loader',
        options: {
            configFile: undefined
        }
    }
]

2. Now build: yarn run build

Location of a Minimal Repository that Demonstrates the Issue.

Apply this diff in this repo:

diff --git a/examples/vanilla/webpack.config.js b/examples/vanilla/webpack.config.js
index 32e454fe..ae9fb98d 100644
--- a/examples/vanilla/webpack.config.js
+++ b/examples/vanilla/webpack.config.js
@@ -13,7 +13,10 @@ module.exports = {
         rules: [
             {
                 test: /\.tsx?$/,
-                loader: 'ts-loader'
+                loader: 'ts-loader',
+                options: {
+                    configFile: undefined
+                }
             }
         ]
     },

[johnnyreilly]

Thanks for this. I'm on a train and slightly tipsy, but on the face of it I think you're probably right. Ideally I'd expect undefined to be treated as if the configFile property has been omitted entirely.

Feels like it's probably an easy fix. If you'd like to submit a PR I'll happily review it. Failing that I'll likely take a look at some point.

[johnnyreilly]

Prospective fix PR is up - just waiting for GitHub Actions to get happy again; there seem to be some issues.

[johnnyreilly]

And apropos of nothing, amazing work on https://code2020.dev/ - it's a gift to the community! ❤️ 🌻

[johnnyreilly]

Shipping with /~https://github.com/TypeStrong/ts-loader/releases/tag/v9.2.4 - should appear as soon as this gets run /~https://github.com/TypeStrong/ts-loader/runs/3149744280?check_suite_focus=true