Ruby: add downgrade scripts to prepare-db-upgrade.sh

.github/workflows/ruby-qltest.yml

@@ -48,3 +48,11 @@ jobs:
           codeql dataset import -S ql/lib/upgrades/initial/ruby.dbscheme testdb empty.trap
           codeql dataset upgrade testdb --additional-packs ql/lib
           diff -q testdb/ruby.dbscheme ql/lib/ruby.dbscheme
+      - name: Check DB downgrade scripts
+        run: |
+          echo >empty.trap
+          rm -rf testdb; codeql dataset import -S ql/lib/ruby.dbscheme testdb empty.trap
+          codeql resolve upgrades --format=lines --allow-downgrades --additional-packs downgrades \
+           --dbscheme=ql/lib/ruby.dbscheme --target-dbscheme=downgrades/initial/ruby.dbscheme |
+           xargs codeql execute upgrades testdb
+          diff -q testdb/ruby.dbscheme downgrades/initial/ruby.dbscheme

ruby/downgrades/qlpack.yml

@@ -0,0 +1,4 @@
+name: codeql/ruby-downgrades
+groups: ruby
+downgrades: .
+library: true

ruby/scripts/create-extractor-pack.ps1

@@ -7,6 +7,7 @@ rm -Recurse -Force extractor-pack
 mkdir extractor-pack | Out-Null
 cp codeql-extractor.yml, ql\lib\ruby.dbscheme, ql\lib\ruby.dbscheme.stats extractor-pack
 cp -Recurse tools extractor-pack
+cp -Recurse downgrades extractor-pack
 mkdir extractor-pack\tools\win64 | Out-Null
 cp target\release\ruby-extractor.exe extractor-pack\tools\win64\extractor.exe
 cp target\release\ruby-autobuilder.exe extractor-pack\tools\win64\autobuilder.exe

ruby/scripts/create-extractor-pack.sh

@@ -17,7 +17,7 @@ codeql query format -i ql/lib/codeql/ruby/ast/internal/TreeSitter.qll
 
 rm -rf extractor-pack
 mkdir -p extractor-pack
-cp -r codeql-extractor.yml tools ql/lib/ruby.dbscheme ql/lib/ruby.dbscheme.stats extractor-pack/
+cp -r codeql-extractor.yml downgrades tools ql/lib/ruby.dbscheme ql/lib/ruby.dbscheme.stats extractor-pack/
 mkdir -p extractor-pack/tools/${platform}
 cp target/release/ruby-extractor extractor-pack/tools/${platform}/extractor
 cp target/release/ruby-autobuilder extractor-pack/tools/${platform}/autobuilder

ruby/scripts/prepare-db-upgrade.sh

@@ -63,6 +63,7 @@ fi
 
 scheme_file="ql/lib/ruby.dbscheme"
 upgrade_root="ql/lib/upgrades"
+downgrade_root="downgrades"
 
 check_hash_valid()
 {
@@ -95,12 +96,28 @@ description: <INSERT DESCRIPTION HERE>
 compatibility: full|backwards|partial|breaking
 EOF
 
+# Copy current and new dbscheme into the downgrade dir
+downgradedir="${downgrade_root}/${current_hash}"
+mkdir -p "${downgradedir}"
+
+cp "${scheme_file}" "${downgradedir}/old.dbscheme"
+git cat-file blob "${prev_hash}" > "${downgradedir}/$(basename "${scheme_file}")"
+
+# Create the template upgrade.properties file.
+cat <<EOF > "${downgradedir}/upgrade.properties"
+description: <INSERT DESCRIPTION HERE>
+compatibility: full|backwards|partial|breaking
+EOF
+
 # Tell user what we've done
 cat <<EOF
 Created upgrade directory here:
   ${upgradedir}
+Created downgrade directory here:
+  ${downgradedir}
 
 Please update:
   ${upgradedir}/upgrade.properties
-with appropriate upgrade instructions
+  ${downgradedir}/upgrade.properties
+with appropriate instructions
 EOF