Don't generate sourcemap for inline generation with fallback=false

[ptlis]

This PR contains a:

• bugfix
• new feature
• code refactor
• test update
• typo fix
• metadata update

Motivation / Use-Case

I'm using typescript, and with inline=true and fallback=false. I get a sourcemap being incorrectly generated for a js file that isn't created.

Breaking Changes

None that I'm aware of.

Additional Info

n/a

[jsf-clabot]

All committers have signed the CLA.

[shockey]

I needed this PR, ended up writing a plugin that achieved something similar:

class RemoveSourcemapsLackingMatchingAssetsPlugin {
  apply(compiler) {
    // Specify the event hook to attach to
    compiler.hooks.emit.tap(
      'RemoveSourcemapsLackingMatchingAssetsPlugin',
      (compilation) => {
        const assetNames = Object.keys(compilation.assets)

        const sourcemapAssetNames = assetNames.filter(str => str.endsWith(".map"))

        const sourcemapAssetsWithoutMatchingSourceAsset = sourcemapAssetNames.filter(name => {
          return assetNames.indexOf(
            name.slice(0, -4)
          ) === -1
        })

        sourcemapAssetsWithoutMatchingSourceAsset.forEach(name => {
          console.warn(`RemoveSourcemapsLackingMatchingAssetsPlugin: blocking emission of "${name}"`)
          delete compilation.assets[name]
        })
      }
    )
  }
}