Enhance coverage reporting with type coverage and summary

Show unified coverage summary with both v8 code coverage and TypeScript type coverage. Calculate cumulative percentage to provide holistic coverage metric. Clean output masks verbose test details and displays only summary statistics.

Author: jdalton

scripts/cover.mjs

@@ -0,0 +1,116 @@
+/**
+ * @fileoverview Coverage script that runs tests with coverage reporting.
+ * Masks test output and shows only the coverage summary.
+ */
+
+import path from 'node:path'
+import { fileURLToPath } from 'node:url'
+
+import { printError, printHeader, printSuccess } from './utils/cli-helpers.mjs'
+import { runCommandQuiet } from './utils/run-command.mjs'
+
+const __dirname = path.dirname(fileURLToPath(import.meta.url))
+const rootPath = path.join(__dirname, '..')
+
+printHeader('Running Coverage')
+
+// Run vitest with coverage enabled, capturing output
+const vitestArgs = [
+  'exec',
+  'vitest',
+  'run',
+  '--coverage',
+  ...process.argv.slice(2),
+]
+const typeCoverageArgs = ['exec', 'type-coverage']
+
+try {
+  const { exitCode, stdout, stderr } = await runCommandQuiet(
+    'pnpm',
+    vitestArgs,
+    {
+      cwd: rootPath,
+    },
+  )
+
+  // Run type coverage
+  const typeCoverageResult = await runCommandQuiet('pnpm', typeCoverageArgs, {
+    cwd: rootPath,
+  })
+
+  // Combine and clean output - remove ANSI color codes and spinner artifacts
+  const ansiRegex = new RegExp(`${String.fromCharCode(27)}\\[[0-9;]*m`, 'g')
+  const output = (stdout + stderr)
+    .replace(ansiRegex, '') // Remove ANSI color codes
+    .replace(/(?:✧|︎|⚡)\s*/g, '') // Remove spinner artifacts
+    .trim()
+
+  // Extract test summary (Test Files ... Duration)
+  const testSummaryMatch = output.match(
+    /Test Files\s+\d+[^\n]*\n[\s\S]*?Duration\s+[\d.]+m?s[^\n]*/,
+  )
+
+  // Extract coverage summary: header + All files row
+  // Match from "% Coverage" header through the All files line and closing border
+  const coverageHeaderMatch = output.match(
+    / % Coverage report from v8\n([-|]+)\n([^\n]+)\n\1/,
+  )
+  const allFilesMatch = output.match(/All files\s+\|\s+([\d.]+)\s+\|[^\n]*/)
+
+  // Extract type coverage percentage
+  const typeCoverageOutput = (
+    typeCoverageResult.stdout + typeCoverageResult.stderr
+  ).trim()
+  const typeCoverageMatch = typeCoverageOutput.match(/\([\d\s/]+\)\s+([\d.]+)%/)
+
+  // Display clean output
+  if (testSummaryMatch) {
+    console.log()
+    console.log(testSummaryMatch[0])
+    console.log()
+  }
+
+  if (coverageHeaderMatch && allFilesMatch) {
+    console.log(' % Coverage report from v8')
+    console.log(coverageHeaderMatch[1]) // Top border
+    console.log(coverageHeaderMatch[2]) // Header row
+    console.log(coverageHeaderMatch[1]) // Middle border
+    console.log(allFilesMatch[0]) // All files row
+    console.log(coverageHeaderMatch[1]) // Bottom border
+    console.log()
+
+    // Display type coverage and cumulative summary
+    if (typeCoverageMatch) {
+      const codeCoveragePercent = Number.parseFloat(allFilesMatch[1])
+      const typeCoveragePercent = Number.parseFloat(typeCoverageMatch[1])
+      const cumulativePercent = (
+        (codeCoveragePercent + typeCoveragePercent) /
+        2
+      ).toFixed(2)
+
+      console.log(' Coverage Summary')
+      console.log(' ───────────────────────────────')
+      console.log(` Type Coverage: ${typeCoveragePercent.toFixed(2)}%`)
+      console.log(` Code Coverage: ${codeCoveragePercent.toFixed(2)}%`)
+      console.log(' ───────────────────────────────')
+      console.log(` Cumulative:    ${cumulativePercent}%`)
+      console.log()
+    }
+  }
+
+  if (exitCode === 0) {
+    printSuccess('Coverage completed successfully')
+  } else {
+    printError('Coverage failed')
+    // Show relevant output on failure for debugging
+    if (!testSummaryMatch && !coverageMatch) {
+      console.log('\n--- Output ---')
+      console.log(output)
+    }
+  }
+
+  process.exitCode = exitCode
+} catch (error) {
+  printError(`Coverage script failed: ${error.message}`)
+  process.exitCode = 1
+}