Allow disabling markdown check steps in the default build test (knati…

…ve#391)

* Allow disabling markdown check steps in the default build test

* Update comment in script

* Update documentation

scripts/README.md

@@ -12,16 +12,23 @@ This is a helper script to run the presubmit tests. To use it:
 1. [optional] Define the function `build_tests()`. If you don't define this
    function, the default action for running the build tests is to:
 
-   - lint and link check markdown files
+   - check markdown files
    - run `go build` on the entire repo
    - run `/hack/verify-codegen.sh` (if it exists)
-   - check licenses in `/cmd` (if it exists)
+   - check licenses in all go packages
 
    The markdown link checker tools doesn't check `localhost` links by default.
    Its configuration file, `markdown-link-check-config.json`, lives in the
    `test-infra/scripts` directory. To override it, create a file with the same
    name, containing the custom config in the `/test` directory.
 
+1. [optional] Customize the default build test runner, if you're using it. Set
+   the following environment variables if the default values don't fit your needs:
+
+   - `DISABLE_MD_LINTING`: Disable linting markdown files, defaults to 0 (false).
+   - `DISABLE_MD_LINK_CHECK`: Disable checking links in markdown files, defaults
+     to 0 (false).
+
 1. [optional] Define the functions `pre_build_tests()` and/or
    `post_build_tests()`. These functions will be called before or after the
    build tests (either your custom one or the default action) and will cause

scripts/presubmit-tests.sh

@@ -19,6 +19,10 @@
 
 source $(dirname ${BASH_SOURCE})/library.sh
 
+# Custom configuration of presubmit tests
+readonly DISABLE_MD_LINTING=${DISABLE_MD_LINTING:-0}
+readonly DISABLE_MD_LINK_CHECK=${DISABLE_MD_LINK_CHECK:-0}
+
 # Extensions or file patterns that don't require presubmit tests.
 readonly NO_PRESUBMIT_FILES=(\.png \.gitignore \.gitattributes ^OWNERS ^OWNERS_ALIASES ^AUTHORS)
 
@@ -103,21 +107,33 @@ function run_build_tests() {
   return ${failed}
 }
 
-# Default build test runner that:
-# * lint and link check markdown files
-# * `go build` on the entire repo
-# * run `/hack/verify-codegen.sh` (if it exists)
-# * check licenses in `/cmd` (if it exists)
-function default_build_test_runner() {
-  local failed=0
-  # Ignore markdown files in /vendor
+# Perform markdown build tests if necessary, unless disabled.
+function markdown_build_tests() {
+  (( DISABLE_MD_LINTING && DISABLE_MD_LINK_CHECK )) && return 0
+  # Get changed markdown files (ignore /vendor)
   local mdfiles="$(echo "${CHANGED_FILES}" | grep \.md$ | grep -v ^vendor/)"
-  if [[ -n "${mdfiles}" ]]; then
+  [[ -z "${mdfiles}" ]] && return 0
+  local failed=0
+  if (( ! DISABLE_MD_LINTING )); then
     subheader "Linting the markdown files"
     lint_markdown ${mdfiles} || failed=1
+  fi
+  if (( ! DISABLE_MD_LINK_CHECK )); then
     subheader "Checking links in the markdown files"
     check_links_in_markdown ${mdfiles} || failed=1
   fi
+  return ${failed}
+}
+
+# Default build test runner that:
+# * check markdown files
+# * `go build` on the entire repo
+# * run `/hack/verify-codegen.sh` (if it exists)
+# * check licenses in all go packages
+function default_build_test_runner() {
+  local failed=0
+  # Perform markdown build checks first
+  markdown_build_tests || failed=1
   # For documentation PRs, just check the md files
   (( IS_DOCUMENTATION_PR )) && return ${failed}
   # Ensure all the code builds