fix(coverage): don't panic if all covered files are ignored via directive (#29250)

Closes https://github.com/denoland/deno/issues/29218

cli/tools/coverage/mod.rs

@@ -740,6 +740,12 @@ pub fn cover_files(
     }
   }
 
+  // All covered files, might have had ignore directive and we can end up
+  // with no reports at this point.
+  if file_reports.is_empty() {
+    return Err(anyhow!("No covered files included in the report"));
+  }
+
   for reporter in reporters {
     reporter.done(&coverage_root, &file_reports);
   }

cli/tools/coverage/reporter.rs

@@ -18,7 +18,7 @@ use super::CoverageReport;
 use crate::args::CoverageType;
 use crate::colors;
 
-#[derive(Default)]
+#[derive(Default, Debug)]
 pub struct CoverageStats<'a> {
   pub line_hit: usize,
   pub line_miss: usize,

tests/specs/coverage/all_files_with_ignore_directives/__test__.jsonc

@@ -0,0 +1,6 @@
+{
+  "tempDir": true,
+  "args": "test --coverage test.ts",
+  "output": "test_coverage.out",
+  "exitCode": 0
+}

tests/specs/coverage/all_files_with_ignore_directives/lib.ts

@@ -0,0 +1,5 @@
+// deno-coverage-ignore-file
+
+export function foo() {
+  return "foo";
+}

tests/specs/coverage/all_files_with_ignore_directives/test.ts

@@ -0,0 +1,5 @@
+import { foo } from "./lib.ts";
+
+Deno.test("test", () => {
+  foo();
+});

tests/specs/coverage/all_files_with_ignore_directives/test_coverage.out

@@ -0,0 +1,7 @@
+Check [WILDCARD]/test.ts
+running 1 test from ./test.ts
+test ... ok ([WILDCARD])
+
+ok | 1 passed | 0 failed ([WILDCARD])
+
+Error generating coverage report: No covered files included in the report