ENH: add ability to test examples PR against PR in bids-specification

.github/pull_request_template.md

@@ -0,0 +1,13 @@
+<!-- New examples often relate to in-progress changes to the specification or validator. Link to the relevant PRs, if any. -->
+
+- BIDS Specification PR: NONE
+- BIDS Validator PR: NONE
+- TODOs:
+  - [ ] ...
+
+<!-- PLEASE READ AND DELETE THE TEXT BELOW BEFORE OPENING THE PULL REQUEST -->
+
+See the [CONTRIBUTING](https://github.com/bids-standard/bids-examples/blob/master/CONTRIBUTING.md) guide. Specifically:
+
+- Please keep the title of your Pull Request (PR) short but informative - it will appear in the changelog.
+

.github/workflows/validate_datasets.yml

@@ -4,6 +4,7 @@ on:
   push:
     branches: ['**']
   pull_request:
+    types: [opened, synchronize, reopened, edited]
     branches: ['**']
   create:
     branches: [master]
@@ -21,16 +22,54 @@ defaults:
     shell: bash
 
 jobs:
+  # Prepare the matrix dynamically based on whether a bids-specification PR is referenced
+  prepare-matrix:
+    runs-on: ubuntu-latest
+    outputs:
+      matrix: ${{ steps.set-matrix.outputs.matrix }}
+      spec_pr: ${{ steps.find-pr.outputs.spec_pr }}
+      val_pr: ${{ steps.find-pr.outputs.val_pr }}
+    steps:
+    - uses: actions/checkout@v5
+      with:
+        fetch-depth: 0  # Get full history for commit message scanning
+
+    - name: Check for bids-specification PR reference
+      id: find-pr
+      run: |
+        # Check PR description if this is a PR
+        if [ "${{ github.event_name }}" == "pull_request" ]; then
+          cat << 'EOF' > /tmp/pr_body.txt
+        ${{ github.event.pull_request.body }}
+        EOF
+          SPEC_PR=$(grep -oP 'BIDS Specification PR:\s*(https://github\.com/bids-standard/bids-specification/pulls?/|bids-standard/bids-specification#)*\K[0-9]+' /tmp/pr_body.txt | head -1 || true)
+          [ -n "$SPEC_PR" ] && echo "spec_pr=$SPEC_PR" >> $GITHUB_OUTPUT || :
+          VAL_PR=$(grep -oP 'BIDS Validator PR:\s*(https://github\.com/bids-standard/bids-validator/pulls?/|bids-standard/bids-validator#)*\K[0-9]+' /tmp/pr_body.txt | head -1 || true)
+          [ -n "$VAL_PR" ] && echo "val_pr=$VAL_PR" >> $GITHUB_OUTPUT || :
+        fi
+
+    - name: Set matrix
+      id: set-matrix
+      run: |
+        EXTRA_ITEM=''
+        if [ -n "${{ steps.find-pr.outputs.spec_pr }}${{ steps.find-pr.outputs.val_pr }}" ]; then
+          EXTRA_ITEM=', "dev-prs"'
+        fi
+        echo "matrix=[\"stable\", \"main\", \"dev\", \"legacy\"${EXTRA_ITEM}]" >> $GITHUB_OUTPUT
+
   build:
+    needs: prepare-matrix
     strategy:
       fail-fast: false
       matrix:
         platform: [ubuntu-latest, macos-latest, windows-latest]
-        bids-validator: [stable, main, dev, legacy]
+        bids-validator: ${{ fromJson(needs.prepare-matrix.outputs.matrix) }}
 
     runs-on: ${{ matrix.platform }}
 
     env:
+      SPEC_PR: ${{ needs.prepare-matrix.outputs.spec_pr }}
+      VAL_PR: ${{ needs.prepare-matrix.outputs.val_pr }}
       TZ: Europe/Berlin
       FORCE_COLOR: 1
 
@@ -73,7 +112,7 @@ jobs:
         deno install -Agf https://github.com/bids-standard/bids-validator/raw/deno-build/bids-validator.js
 
     - name: Install BIDS validator (dev)
-      if: matrix.bids-validator == 'dev'
+      if: ( matrix.bids-validator == 'dev' ) || ( matrix.bids-validator == 'dev-prs' && env.VAL_PR == '' )
       run: |
         git clone -b dev https://github.com/bids-standard/bids-validator/ ../bids-validator
         cd ../bids-validator
@@ -84,6 +123,25 @@ jobs:
       run: |
         npm install -g bids-validator
 
+    - name: Install BIDS validator (dev-prs with VAL_PR)
+      if: matrix.bids-validator == 'dev-prs' && env.VAL_PR != ''
+      shell: bash
+      env:
+        GH_TOKEN: ${{ github.token }}
+      run: |
+        # Fetch PR info using gh cli (handles auth automatically)
+        fork_url=$(gh api repos/bids-standard/bids-validator/pulls/${{ env.VAL_PR }} --jq '.head.repo.html_url')
+        branch=$(gh api repos/bids-standard/bids-validator/pulls/${{ env.VAL_PR }} --jq '.head.ref')
+        echo "I: Received fork_url=$fork_url branch=$branch"
+        if [ "$fork_url" = "null" ] || [ -z "$fork_url" ]; then
+          echo "E: Failed to get PR info for VAL_PR=${{ env.VAL_PR }}"
+          exit 1
+        fi
+        # Perform the same installation as in "dev"
+        git clone -b "$branch" "$fork_url" ../bids-validator
+        cd ../bids-validator
+        deno compile -A -o $HOME/.deno/bin/bids-validator src/bids-validator.ts
+
     - name: Display versions and environment information
       run: |
         echo $TZ
@@ -131,6 +189,13 @@ jobs:
       # release of https://jsr.io/@bids/schema
       run: echo BIDS_SCHEMA=https://bids-specification.readthedocs.io/en/latest/schema.json >> $GITHUB_ENV
 
+    - name: Set BIDS_SCHEMA variable for dev-prs version
+      if: matrix.bids-validator == 'dev-prs' && env.SPEC_PR != ''
+      # Use the readthedocs PR preview build for the schema
+      run: |
+        echo "Using schema from bids-specification PR #${{ env.SPEC_PR }}"
+        echo BIDS_SCHEMA=https://bids-specification--${{ env.SPEC_PR }}.org.readthedocs.build/en/${{ env.SPEC_PR }}/schema.json >> $GITHUB_ENV
+
     - name: Validate all BIDS datasets using bids-validator
       run: |
         cat ./run_tests.sh