ci: add strict-no-cover to detect unnecessary coverage pragmas

Add strict-no-cover from pydantic to CI pipeline. This tool identifies
`# pragma: no cover` comments on lines that are actually covered by
tests, helping keep coverage pragmas accurate.

Changes:
- Add strict-no-cover as dev dependency (installed from git)
- Add `pragma: lax no cover` to coverage exclude_lines for partial coverage
- Add CI step to run strict-no-cover after coverage report (Linux only
due to a Windows bug in the tool)
- Pin coverage to <=7.13 (7.13.1 introduced a regression that breaks
strict-no-cover by changing how source paths are reported in .coverage
databases)
- Remove relative_files=true from [tool.coverage.run] as it interferes
with strict-no-cover path matching

Author: maxisbey

.github/workflows/shared.yml

@@ -62,6 +62,10 @@ jobs:
           uv run --frozen --no-sync coverage combine
           uv run --frozen --no-sync coverage report
 
+      - name: Check for unnecessary no cover pragmas
+        if: runner.os != 'Windows'
+        run: uv run --frozen --no-sync strict-no-cover
+
   readme-snippets:
     runs-on: ubuntu-latest
     steps:

pyproject.toml

@@ -66,8 +66,9 @@ dev = [
     "pytest-pretty>=1.2.0",
     "inline-snapshot>=0.23.0",
     "dirty-equals>=0.9.0",
-    "coverage[toml]>=7.13.1",
+    "coverage[toml]>=7.10.7,<=7.13",
     "pillow>=12.0",
+    "strict-no-cover",
 ]
 docs = [
     "mkdocs>=1.6.1",
@@ -163,6 +164,7 @@ members = ["examples/clients/*", "examples/servers/*", "examples/snippets"]
 
 [tool.uv.sources]
 mcp = { workspace = true }
+strict-no-cover = { git = "https://github.com/pydantic/strict-no-cover" }
 
 [tool.pytest.ini_options]
 log_cli = true
@@ -198,7 +200,6 @@ branch = true
 patch = ["subprocess"]
 concurrency = ["multiprocessing", "thread"]
 source = ["src", "tests"]
-relative_files = true
 omit = [
     "src/mcp/client/__main__.py",
     "src/mcp/server/__main__.py",
@@ -215,6 +216,7 @@ ignore_errors = true
 precision = 2
 exclude_lines = [
     "pragma: no cover",
+    "pragma: lax no cover",
     "if TYPE_CHECKING:",
     "@overload",
     "raise NotImplementedError",