unknown filename with some different configuration in optimization.splitChunks

[geekxue]

Bug report

The configuration of optimization.splitChunks is

optimization: {
        usedExports:true,
        splitChunks: {
            chunks: "all",
            cacheGroups: {
                test:/[\\/]node_modules[\\/]/,
            }
        }
    },

What is the current behavior?
It works and bundle the chunk with the name "test~lodash.chunk.js"

If the current behavior is a bug, please provide the steps to reproduce.

The office website about SplitChunksPlugin tells us that "splitChunks.cacheGroups.{cacheGroup}.test" controls which modules are selected by this cache group. It only chooses modules but not defines the name of chunk

What is the expected behavior?
If the code with such configuration should bundle the chunk with the name "vendors~lodash.chunk.js"

Other relevant information:
webpack version: 4.31.0
Node.js version: v10.15.1
Operating System: Mac OS 10.14.6
Additional tools:

[sokra]

     optimization: {
         usedExports:true,
         splitChunks: {
             chunks: "all",
             cacheGroups: {
+                vendors: {
                     test:/[\\/]node_modules[\\/]/,
+                }
             }
         }
     },

[alexander-akait]

@sokra maybe we can improve schema?