ci: add coverage job

Uses the new llvm source-base coverage from nightly to generate coverage
reports:
- full html report as artifact
- cobertura report for gitlab MR integration
- output coverage summary for gitlab parsing

Here is the regexp to set in gitlab as "Test coverage parsing":
\s*lines\.*:\s*([\d\.]+%)

Ignore sys crates when calculating coverage are those are fully
generated anyway.

Resources:
- https://github.com/marco-c/rust-code-coverage-sample
- mozilla/grcov#468 (comment)
- https://www.greycastle.se/how-to-show-flutter-test-coverage-in-gitlab-ci/

.gitlab-ci.yml

@@ -81,7 +81,7 @@ stages:
   - .fdo.container-build@debian
   stage: container-base
   variables:
-    FDO_DISTRIBUTION_PACKAGES: "build-essential curl python3-setuptools liborc-0.4-dev libglib2.0-dev libxml2-dev libgtk-3-dev libegl1-mesa libgles2-mesa libgl1-mesa-dri libgl1-mesa-glx libwayland-egl1-mesa xz-utils libssl-dev git wget ca-certificates ninja-build python3-pip flex bison libglib2.0-dev"
+    FDO_DISTRIBUTION_PACKAGES: "build-essential curl python3-setuptools liborc-0.4-dev libglib2.0-dev libxml2-dev libgtk-3-dev libegl1-mesa libgles2-mesa libgl1-mesa-dri libgl1-mesa-glx libwayland-egl1-mesa xz-utils libssl-dev git wget ca-certificates ninja-build python3-pip flex bison libglib2.0-dev lcov"
     FDO_DISTRIBUTION_EXEC: 'bash ci/install-gst.sh && pip3 install git+http://gitlab.freedesktop.org/freedesktop/ci-templates'
 
 .build-final-image:
@@ -191,9 +191,7 @@ plugins-update-nightly:
   variables:
     UPDATE_IMG: "nightly"
 
-.cargo test:
-  stage: "test"
-  script:
+.cargo_test_var: &cargo_test
     - rustc --version
       # First build and test all the crates with their relevant features
       # Keep features in sync with below
@@ -229,6 +227,11 @@ plugins-update-nightly:
         cargo build --locked --color=always --manifest-path tutorials/Cargo.toml --bins --examples --all-features
       fi
 
+.cargo test:
+  stage: "test"
+  script:
+    - *cargo_test
+
 test msrv:
   extends:
     - '.cargo test'
@@ -413,6 +416,31 @@ outdated:
   script:
     - cargo outdated --color=always --root-deps-only --exit-code 1 -v
 
+coverage:
+  extends:
+    - '.cargo test'
+    - .img-nightly
+  stage: 'extras'
+  variables:
+    ALL_FEATURES: 'yes'
+    RUSTFLAGS: "-Zinstrument-coverage"
+    LLVM_PROFILE_FILE: "gstreamer-rs-%p-%m.profraw"
+  script:
+    - *cargo_test
+    # generate html report
+    - grcov . --binary-path ./target/debug/ -s . -t html --branch --ignore-not-existing --ignore "*target*" --ignore "*/sys/*" --ignore "examples/*" --ignore "tutorials/*" -o ./coverage/
+    # generate cobertura report for gitlab integration
+    - grcov . --binary-path ./target/debug/ -s . -t lcov --branch --ignore-not-existing --ignore "*target*" --ignore "*/sys/*" --ignore "examples/*" --ignore "tutorials/*" -o lcov
+    - python3 /usr/local/lib/python3.7/dist-packages/lcov_cobertura.py lcov
+    # output coverage summary for gitlab parsing
+    - lcov -r lcov "/*" 2&> out
+    - grep lines out
+  artifacts:
+    paths:
+      - 'coverage'
+    reports:
+      cobertura: coverage.xml
+
 pages:
   extends: .img-stable
   stage: 'deploy'

ci/images_template.yml

@@ -1,4 +1,4 @@
 variables:
-  GST_RS_IMG_TAG: '2020-12-31.0'
+  GST_RS_IMG_TAG: '2021-01-11.0'
   GST_RS_STABLE: '1.49.0'
   GST_RS_MSRV: '1.48.0'

ci/install-rust.sh

@@ -26,3 +26,10 @@ if [ "$RUST_IMAGE_FULL" = "1" ]; then
   cargo install --force cargo-deny
   cargo install --force cargo-outdated
 fi
+
+# coverage tools
+if [ "$RUST_VERSION" = "nightly" ]; then
+  cargo install grcov
+  rustup component add llvm-tools-preview
+  pip3 install lcov_cobertura
+fi