Auto-trigger release pipeline on main merge and add version check (#3335)

* Auto-trigger release pipeline on main merge and add version check

* Simplify trigger syntax in publish-release.yml

Author: msyyc

README.md

@@ -37,7 +37,7 @@ pnpm clean
 **Semi-auto:**
 
 Follow https://github.com/Azure/autorest.python/blob/main/.github/skills/bump-and-release/SKILL.md to make a release PR. 
-After it merged, trigger [release pipeline](https://dev.azure.com/azure-sdk/internal/_build?definitionId=1668) to release new version.
+After it merged, [release pipeline](https://dev.azure.com/azure-sdk/internal/_build?definitionId=1668) will be triggered automatically to release new version.
 
 ## Contributing
 

eng/pipelines/publish-release.yml

@@ -1,5 +1,6 @@
-# This is a manual pipeline, don't trigger automatically
-trigger: none
+# Trigger only after PR merged into main
+trigger:
+  - main
 pr: none
 
 extends: 
@@ -28,6 +29,31 @@ extends:
                   inputs:
                       versionSpec: 3.10
 
+                - script: |
+                      set -e
+                      
+                      # Check @azure-tools/typespec-python
+                      TYPESPEC_VERSION=$(node -p "require('./packages/typespec-python/package.json').version")
+                      echo "Checking if @azure-tools/typespec-python@$TYPESPEC_VERSION is already published..."
+                      if npm view @azure-tools/typespec-python@$TYPESPEC_VERSION version 2>/dev/null; then
+                        echo "##vso[task.logissue type=error]@azure-tools/typespec-python@$TYPESPEC_VERSION is already published to npm"
+                        exit 1
+                      fi
+                      echo "@azure-tools/typespec-python@$TYPESPEC_VERSION is not yet published"
+                      
+                      # Check @autorest/python
+                      AUTOREST_VERSION=$(node -p "require('./packages/autorest.python/package.json').version")
+                      echo "Checking if @autorest/python@$AUTOREST_VERSION is already published..."
+                      if npm view @autorest/python@$AUTOREST_VERSION version 2>/dev/null; then
+                        echo "##vso[task.logissue type=error]@autorest/python@$AUTOREST_VERSION is already published to npm"
+                        exit 1
+                      fi
+                      echo "@autorest/python@$AUTOREST_VERSION is not yet published"
+                      
+                      echo "Version check passed. Proceeding with build and tests."
+                  displayName: Check if versions are already published
+                  workingDirectory: $(Build.SourcesDirectory)
+
                 - script: npm install -g pnpm@9.5.0
                   displayName: Install PNPM 9.5.0