No coverage for vue.js single file components written in typescript

We have a project set up that includes vuejs, typescript, and jest 24.9 to produce an lcov.info which is then passed to sonar with a sonar-project.properties file like…

sonar.sources=src
sonar.exclusions=public/**
sonar.javascript.lcov.reportPaths=coverage/lcov.info

The vuejs components are like…

<template src="./html.html"></template>
<script src="./typescript.ts" lang="ts"></script>
<style></style>

that is to say they use a src attribute to include the script.

Components like this display 0 coverage in sonar… however, if the component is written like…

<template>
  <div>
    <div>{{ a }}</div>
    <button @click="plus()">add 1</button>
  </div>
</template>

<script lang="ts">
import Vue from 'vue';

export default Vue.extend({
  data() {
    return {
      a: 1,
    };
  },

  methods: {
    plus() {
      this.a++;
    },
  },
});
</script>

<style scoped></style>

then coverage seems to display correctly in sonar.
The coverage html report that jest creates is correct for both cases.
I thought that perhaps the problem might be that the lcov.info generated by jest had absolute paths to source files in it, so I converted these to relative paths and I could have sworn this fixed it in sonar and I started to see coverage properly. However, then it seemed to stop working to maybe I was just mistaken.

jest config is…

{
  preset: '@vue/cli-plugin-unit-jest/presets/typescript-and-babel',
  coverageDirectory: 'coverage',
  collectCoverage: true,
  collectCoverageFrom: [
    'src/**/**/*.vue',
    '!src/**/**/*.ts',
    '!src/**/main.js',
    '!src/**/featureFlagger.ts',
    '!src/**/registerServiceWorker.ts',
    '!src/**/interfaces/*',
  ],
  coverageReporters: ['lcov'],
  globalSetup: './globalSetup.js',
  testMatch: ['**/?(*.)+(spec|test).[jt]s?(x)'],
}

Can anyone offer any guidance?

Thanks in advance.