From 2755d5d0ab459606eeaa1172def50d4f6cdb9283 Mon Sep 17 00:00:00 2001
From: Pratik Mahalle <mahallepratik683@gmail.com>
Date: Sun, 22 Feb 2026 11:59:00 +0530
Subject: [PATCH] [chore] Auto-generate PR from changelog (#42123)

Add GitHub workflow to parse .chloggen/*.yaml and populate PR title/body
when title matches 'as per changelog'.
---
 .../workflows/generate-pr-from-changelog.yml  |  40 ++++
 .../scripts/generate-pr-from-changelog.sh     | 215 ++++++++++++++++++
 CONTRIBUTING.md                               |   5 +-
 3 files changed, 259 insertions(+), 1 deletion(-)
 create mode 100644 .github/workflows/generate-pr-from-changelog.yml
 create mode 100755 .github/workflows/scripts/generate-pr-from-changelog.sh

diff --git a/.github/workflows/generate-pr-from-changelog.yml b/.github/workflows/generate-pr-from-changelog.yml
new file mode 100644
index 0000000000000..b8b7a0e4d7ca6
--- /dev/null
+++ b/.github/workflows/generate-pr-from-changelog.yml
@@ -0,0 +1,40 @@
+# This workflow generates a PR title and body from changelog entry YAML files
+# when the PR title contains "as per changelog" (case-insensitive).
+#
+# This allows contributors to write their changelog entry first, then simply
+# set the PR title to "as per changelog" to have the PR information auto-populated.
+#
+# See: https://github.com/open-telemetry/opentelemetry-collector-contrib/issues/42123
+
+name: 'Generate PR from changelog'
+on:
+  pull_request_target:
+    types:
+      - opened
+      - edited
+
+permissions: read-all
+
+jobs:
+  generate-pr-from-changelog:
+    permissions:
+      pull-requests: write
+      contents: read
+    runs-on: ubuntu-24.04
+    if: >-
+      github.actor != 'dependabot[bot]'
+      && github.repository_owner == 'open-telemetry'
+      && (contains(github.event.pull_request.title, 'as per changelog')
+        || contains(github.event.pull_request.title, 'as per chloggen'))
+    steps:
+      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6
+        with:
+          fetch-depth: 0
+
+      - name: Generate PR title and body from changelog
+        run: ./.github/workflows/scripts/generate-pr-from-changelog.sh
+        env:
+          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          REPO: ${{ github.repository }}
+          PR: ${{ github.event.number }}
+          PR_HEAD: ${{ github.event.pull_request.head.sha }}
diff --git a/.github/workflows/scripts/generate-pr-from-changelog.sh b/.github/workflows/scripts/generate-pr-from-changelog.sh
new file mode 100755
index 0000000000000..af8660aa5bdf7
--- /dev/null
+++ b/.github/workflows/scripts/generate-pr-from-changelog.sh
@@ -0,0 +1,215 @@
+#!/usr/bin/env bash
+#
+# Copyright The OpenTelemetry Authors
+# SPDX-License-Identifier: Apache-2.0
+#
+# Generates a PR title and body from changelog entry YAML files
+# when the PR title contains "as per changelog" (case-insensitive).
+#
+# Required environment variables:
+#   REPO    - The GitHub repository (e.g. "open-telemetry/opentelemetry-collector-contrib")
+#   PR      - The PR number
+#   PR_HEAD - The HEAD SHA of the PR
+
+set -euo pipefail
+
+if [[ -z "${REPO:-}" || -z "${PR:-}" || -z "${PR_HEAD:-}" ]]; then
+    echo "One or more of REPO, PR, and PR_HEAD have not been set, please ensure each is set."
+    exit 0
+fi
+
+# Map change_type values to human-readable prefixes
+change_type_label() {
+    case "$1" in
+        breaking)       echo "breaking change" ;;
+        deprecation)    echo "deprecation" ;;
+        new_component)  echo "new component" ;;
+        enhancement)    echo "enhancement" ;;
+        bug_fix)        echo "bug fix" ;;
+        *)              echo "$1" ;;
+    esac
+}
+
+main() {
+    # Find changelog YAML files added in this PR (excluding TEMPLATE.yaml, config.yaml)
+    ADDED_FILES=$(git diff --diff-filter=A --name-only "$(git merge-base origin/main "${PR_HEAD}")" "${PR_HEAD}" ./.chloggen/ \
+        | grep -E '\.yaml$' \
+        | grep -v 'TEMPLATE\.yaml' \
+        | grep -v 'config\.yaml' \
+        || true)
+
+    if [[ -z "${ADDED_FILES}" ]]; then
+        echo "No changelog entry YAML files found in this PR. Cannot generate PR info from changelog."
+        exit 0
+    fi
+
+    echo "Found changelog entries:"
+    echo "${ADDED_FILES}"
+
+    # Collect information from all changelog entries
+    COMPONENTS=()
+    NOTES=()
+    CHANGE_TYPES=()
+    ALL_ISSUES=()
+    SUBTEXTS=()
+
+    for FILE in ${ADDED_FILES}; do
+        if [[ ! -f "${FILE}" ]]; then
+            echo "Warning: File ${FILE} not found, skipping."
+            continue
+        fi
+
+        # Parse YAML fields using grep + sed (avoids requiring yq as a dependency)
+        # Extract change_type
+        CHANGE_TYPE=$(grep -E '^change_type:' "${FILE}" | head -1 | sed "s/^change_type:[[:space:]]*//" | sed "s/['\"]//g" | xargs)
+
+        # Extract component
+        COMPONENT=$(grep -E '^component:' "${FILE}" | head -1 | sed "s/^component:[[:space:]]*//" | sed "s/['\"]//g" | xargs)
+
+        # Extract note
+        NOTE=$(grep -E '^note:' "${FILE}" | head -1 | sed "s/^note:[[:space:]]*//" | sed "s/['\"]//g" | xargs)
+
+        # Extract issues (format: issues: [1234] or issues: [1234, 5678])
+        ISSUES=$(grep -E '^issues:' "${FILE}" | head -1 | sed "s/^issues:[[:space:]]*//" | tr -d '[]' | xargs)
+
+        # Extract subtext (can be multiline with pipe |)
+        SUBTEXT_LINE=$(grep -n '^subtext:' "${FILE}" | head -1)
+        SUBTEXT=""
+        if [[ -n "${SUBTEXT_LINE}" ]]; then
+            LINE_NUM=$(echo "${SUBTEXT_LINE}" | cut -d: -f1)
+            SUBTEXT_VALUE=$(echo "${SUBTEXT_LINE}" | sed "s/^[0-9]*:subtext:[[:space:]]*//" | xargs)
+
+            if [[ "${SUBTEXT_VALUE}" == "|" ]]; then
+                # Multiline subtext: read indented lines after the pipe
+                SUBTEXT=$(awk -v start="${LINE_NUM}" '
+                    NR > start {
+                        if (/^[[:space:]]+[^#]/) {
+                            sub(/^[[:space:]]{2}/, ""); print
+                        } else if (/^[[:space:]]*$/) {
+                            print ""
+                        } else {
+                            exit
+                        }
+                    }
+                ' "${FILE}")
+            elif [[ -n "${SUBTEXT_VALUE}" ]]; then
+                # shellcheck disable=SC2001
+                SUBTEXT=$(echo "${SUBTEXT_VALUE}" | sed "s/['\"]//g")
+            fi
+        fi
+
+        if [[ -n "${COMPONENT}" ]]; then
+            COMPONENTS+=("${COMPONENT}")
+        fi
+        if [[ -n "${NOTE}" ]]; then
+            NOTES+=("${NOTE}")
+        fi
+        if [[ -n "${CHANGE_TYPE}" ]]; then
+            CHANGE_TYPES+=("${CHANGE_TYPE}")
+        fi
+        if [[ -n "${ISSUES}" ]]; then
+            # Split comma-separated issues
+            IFS=',' read -ra ISSUE_ARRAY <<< "${ISSUES}"
+            for ISSUE in "${ISSUE_ARRAY[@]}"; do
+                ISSUE=$(echo "${ISSUE}" | xargs)
+                if [[ -n "${ISSUE}" ]]; then
+                    ALL_ISSUES+=("${ISSUE}")
+                fi
+            done
+        fi
+        if [[ -n "${SUBTEXT}" ]]; then
+            SUBTEXTS+=("${SUBTEXT}")
+        fi
+    done
+
+    if [[ ${#NOTES[@]} -eq 0 ]]; then
+        echo "No valid changelog notes found. Cannot generate PR info."
+        exit 0
+    fi
+
+    # --- Generate PR Title ---
+    # Format: [component] note (for single entry)
+    # Format: [component1, component2] first note (+N more) (for multiple entries)
+
+    # Deduplicate components
+    mapfile -t UNIQUE_COMPONENTS < <(echo "${COMPONENTS[@]}" | tr ' ' '\n' | sort -u)
+    COMPONENT_PREFIX=""
+    if [[ ${#UNIQUE_COMPONENTS[@]} -gt 0 ]]; then
+        COMPONENT_PREFIX="[$(IFS=', '; echo "${UNIQUE_COMPONENTS[*]}")] "
+    fi
+
+    if [[ ${#NOTES[@]} -eq 1 ]]; then
+        NEW_TITLE="${COMPONENT_PREFIX}${NOTES[0]}"
+    else
+        # Multiple entries: use the first note, mentioning there are more
+        REMAINING=$(( ${#NOTES[@]} - 1 ))
+        NEW_TITLE="${COMPONENT_PREFIX}${NOTES[0]} (+${REMAINING} more)"
+    fi
+
+    # Truncate title to 256 characters (GitHub limit)
+    if [[ ${#NEW_TITLE} -gt 256 ]]; then
+        NEW_TITLE="${NEW_TITLE:0:253}..."
+    fi
+
+    echo ""
+    echo "Generated PR title: ${NEW_TITLE}"
+
+    # --- Generate PR Body ---
+    BODY="#### Description"$'\n'
+
+    for i in "${!NOTES[@]}"; do
+        CHANGE_LABEL=""
+        if [[ -n "${CHANGE_TYPES[$i]:-}" ]]; then
+            CHANGE_LABEL=$(change_type_label "${CHANGE_TYPES[$i]}")
+        fi
+
+        if [[ ${#NOTES[@]} -eq 1 ]]; then
+            BODY+=$'\n'"**${CHANGE_LABEL^}**: ${NOTES[$i]}"$'\n'
+        else
+            BODY+=$'\n'"- **${CHANGE_LABEL^}** (${COMPONENTS[$i]:-unknown}): ${NOTES[$i]}"$'\n'
+        fi
+    done
+
+    # Add subtext if present
+    if [[ ${#SUBTEXTS[@]} -gt 0 ]]; then
+        BODY+=$'\n'"**Details:**"$'\n'
+        for SUBTEXT in "${SUBTEXTS[@]}"; do
+            if [[ -n "${SUBTEXT}" ]]; then
+                BODY+=$'\n'"${SUBTEXT}"$'\n'
+            fi
+        done
+    fi
+
+    # Add tracking issues
+    BODY+=$'\n'"#### Link to tracking issue"$'\n'
+    if [[ ${#ALL_ISSUES[@]} -gt 0 ]]; then
+        mapfile -t UNIQUE_ISSUES < <(echo "${ALL_ISSUES[@]}" | tr ' ' '\n' | sort -un)
+        for ISSUE in "${UNIQUE_ISSUES[@]}"; do
+            BODY+="Fixes #${ISSUE}"$'\n'
+        done
+    else
+        BODY+="Fixes "$'\n'
+    fi
+
+    BODY+=$'\n'"#### Testing"$'\n\n'
+    BODY+="#### Documentation"$'\n\n'
+
+    BODY+="---"$'\n'
+    BODY+="*This PR description was auto-generated from the changelog entry.*"$'\n'
+
+    echo ""
+    echo "Generated PR body:"
+    echo "${BODY}"
+
+    # --- Update the PR ---
+    echo ""
+    echo "Updating PR #${PR}..."
+
+    gh pr edit "${PR}" --title "${NEW_TITLE}" --body "${BODY}"
+
+    echo "PR #${PR} updated successfully."
+}
+
+# We don't want this workflow to ever fail and block a PR,
+# so ensure all errors are caught.
+main || echo "Failed to run $0"
diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 641c547c7dbca..d2a6ebe74ea4e 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -115,6 +115,10 @@ change. For instance:
 
     [processor/tailsampling] fix AND policy
 
+Alternatively, if you have already written a changelog entry, you can set your PR title to `as per changelog` and a
+GitHub Action will automatically generate the PR title and description from your changelog entry YAML file(s). This
+avoids duplicating effort between the changelog entry and the PR description.
+
 ### Description guidelines
 
 When linking to an open issue, if your PR is meant to close said issue, please prefix your issue with one of the
@@ -122,7 +126,6 @@ following keywords: `Resolves`, `Fixes`, or `Closes`. More information on this f
 [here](https://docs.github.com/en/issues/tracking-your-work-with-issues/linking-a-pull-request-to-an-issue#linking-a-pull-request-to-an-issue-using-a-keyword).
 This will automatically close the issue once your PR has been merged.
 
-
 ## Issue Triaging
 
 See [issue-triaging.md](./issue-triaging.md) for more information on the issue triaging process.