[chore] Allow adding component labels through comments (open-telemetry#15719)

This adds the ability to add and remove component labels using comments, which will allow issue openers to add the label corresponding to a component to ping the code owners, and will enable code owners to update the component labels on an issue if necessary.

There are two relatively minor caveats with the way the add-labels.sh script is currently implemented.

- Labels and comments are added separately, so adding a lot of labels can make things noisy. This can be fixed with additional processing, but I figure this is an uncommon case, so I opted to instead keep the script simple.
- Adding a component label that already is applied will ping the code owners again.

Author: evan-bradley

.github/workflows/add-labels.yml

@@ -5,7 +5,7 @@ on:
 
 jobs:
   add-labels:
-    if: ${{ !github.event.issue.pull_request && (github.event.comment.body == '/help-wanted' || github.event.comment.body == '/good-first-issue' ) }}
+    if: ${{ !github.event.issue.pull_request && startsWith(github.event.comment.body, '/label') }}
 
     runs-on: ubuntu-latest
     steps:
@@ -20,3 +20,4 @@ jobs:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
           ISSUE: ${{ github.event.issue.number }}
           COMMENT: ${{ github.event.comment.body }}
+          SENDER: ${{ github.event.sender.login }}

.github/workflows/scripts/add-labels.sh

@@ -16,15 +16,61 @@
 #
 #
 
-if [ -z "${ISSUE}" ] || [ -z "${COMMENT}" ]; then
+set -euo pipefail
+
+if [[ -z "${ISSUE:-}" || -z "${COMMENT:-}" || -z "${SENDER:-}" ]]; then
+    echo "At least one of ISSUE, COMMENT, or SENDER has not been set, please ensure each is set."
     exit 0
 fi
 
-declare -A labels
-labels["/good-first-issue"]="good first issue"
-labels["/help-wanted"]="help wanted"
-
+CUR_DIRECTORY=$(dirname "$0")
 
-if [ -n "${labels["${COMMENT}"]}" ] ; then
-    gh issue edit "${ISSUE}" --add-label "${labels["${COMMENT}"]}"
+if [[ ${COMMENT:0:6} != "/label" ]]; then
+    echo "Comment is not a label comment, exiting."
+    exit 0
 fi
+
+declare -A COMMON_LABELS
+COMMON_LABELS["good-first-issue"]="good first issue"
+COMMON_LABELS["help-wanted"]="help wanted"
+
+LABELS=$(echo "${COMMENT}" | sed -E 's%^/label%%')
+
+for LABEL_REQ in ${LABELS}; do
+    LABEL=$(echo "${LABEL_REQ}" | sed -E s/^[+-]?//)
+    SHOULD_ADD=true
+
+    if [[ "${LABEL_REQ:0:1}" = "-" ]]; then
+        SHOULD_ADD=false
+    fi
+
+    if [[ -v COMMON_LABELS["${LABEL}"] ]]; then
+        if [[ ${SHOULD_ADD} = true ]]; then
+            gh issue edit "${ISSUE}" --add-label "${COMMON_LABELS["${LABEL}"]}"
+        else
+            gh issue edit "${ISSUE}" --remove-label "${COMMON_LABELS["${LABEL}"]}"
+        fi
+        continue
+    fi
+
+    # Grep exits with status code 1 if there are no matches,
+    # so we manually set RESULT to 0 if nothing is found.
+    RESULT=$(grep -c "${LABEL}" .github/CODEOWNERS || true)
+
+    if [[ ${RESULT} = 0 ]]; then
+        echo "\"${LABEL}\" doesn't correspond to a component, skipping."
+        continue
+    fi
+
+    if [[ ${SHOULD_ADD} = true ]]; then
+        gh issue edit "${ISSUE}" --add-label "${LABEL}"
+
+        # Labels added by a GitHub Actions workflow don't trigger other workflows
+        # by design, so we have to manually ping code owners here.
+        COMPONENT="${LABEL}" ISSUE=${ISSUE} SENDER="${SENDER}" bash "${CUR_DIRECTORY}/ping-codeowners.sh"
+    else
+        gh issue edit "${ISSUE}" --remove-label "${LABEL}"
+    fi
+done
+
+

CONTRIBUTING.md

@@ -160,14 +160,22 @@ in general try to follow them.
 
 ## Adding Labels via Comments
 
-In order to facilitate proper label usage and to empower Code Owners, you are able to add the following labels to issues via comments.
+In order to facilitate proper label usage and to empower Code Owners, you are able to add labels to issues via comments. To add a label through a comment, post a new comment on an issue starting with `/label`, followed by a space-separated list of your desired labels. Supported labels come from the table below, or correspond to a component defined in the [CODEOWNERS file](.github/CODEOWNERS).
 
-| Label              | Generating Comment |
+The following general labels are supported:
+
+| Label              | Label in Comment   |
 |--------------------|--------------------|
-| `good first issue` | /good-first-issue  |
-| `help wanted`      | /help-wanted       |
+| `good first issue` | `good-first-issue` |
+| `help wanted`      | `help-wanted`      |
+
+To delete a label, prepend the label with `-`. Note that you must make a new comment to modify labels; you cannot edit an existing comment.
+
+Example label comment:
 
-Currently, labels can only be created via comment, not deleted.  You must make a new comment; you cannot edit an existing comment.
+```
+/label receiver/prometheus help-wanted -exporter/prometheus
+```
 
 ## Becoming a Code Owner