LibraryConfiguration: extend with allowBRANCH_NAME_PR to let CHANGE_BRANCH and CHANGE_TARGET be considered as fallbacks [JENKINS-69731]

Author: jimklimov

src/main/java/org/jenkinsci/plugins/workflow/libs/LibraryConfiguration.java

@@ -61,6 +61,7 @@ public class LibraryConfiguration extends AbstractDescribableImpl<LibraryConfigu
     private boolean implicit;
     private boolean allowVersionOverride = true;
     private boolean allowBRANCH_NAME = false;
+    private boolean allowBRANCH_NAME_PR = false;
     private boolean includeInChangesets = true;
     private LibraryCachingConfiguration cachingConfiguration = null;
 
@@ -129,6 +130,14 @@ public boolean isAllowBRANCH_NAME() {
         this.allowBRANCH_NAME = allowBRANCH_NAME;
     }
 
+    public boolean isAllowBRANCH_NAME_PR() {
+        return allowBRANCH_NAME_PR;
+    }
+
+    @DataBoundSetter public void setAllowBRANCH_NAME_PR(boolean allowBRANCH_NAME_PR) {
+        this.allowBRANCH_NAME_PR = allowBRANCH_NAME_PR;
+    }
+
     /**
      * Whether to include library changes in reported changes in a job {@link #getIncludeInChangesets}.
      */
@@ -202,6 +211,47 @@ public LibraryCachingConfiguration getCachingConfiguration() {
                 if (fv != null && fv.kind == FormValidation.Kind.OK) {
                     return runVersion;
                 }
+
+                if (runVersion.startsWith("PR-") && allowBRANCH_NAME_PR) {
+                    // MultiBranch Pipeline support for pull requests
+                    // sets BRANCH_NAME="PR-123" and keeps source
+                    // and target branch names in CHANGE_BRANCH and
+                    // CHANGE_TARGET respectively.
+
+                    // First check for possible PR-source branch of
+                    // pipeline coordinated with a PR of trusted
+                    // shared library (if branch exists in library,
+                    // after repo protections involved, it is already
+                    // somewhat trustworthy):
+                    try {
+                        runVersion = run.getEnvironment(listener).get("CHANGE_BRANCH", null);
+                    } catch (Exception x) {
+                        runVersion = null;
+                    }
+                    if (runVersion != null && !("".equals(runVersion))) {
+                        fv = retriever.validateVersion(name, runVersion, runParent);
+
+                        if (fv != null && fv.kind == FormValidation.Kind.OK) {
+                            return runVersion;
+                        }
+                    }
+
+                    // Next check for possible PR-target branch of
+                    // pipeline coordinated with existing version of
+                    // trusted shared library:
+                    try {
+                        runVersion = run.getEnvironment(listener).get("CHANGE_TARGET", null);
+                    } catch (Exception x) {
+                        runVersion = null;
+                    }
+                    if (runVersion != null && !("".equals(runVersion))) {
+                        fv = retriever.validateVersion(name, runVersion, runParent);
+
+                        if (fv != null && fv.kind == FormValidation.Kind.OK) {
+                            return runVersion;
+                        }
+                    }
+                }
             }
 
             // No retriever, or its validateVersion() did not confirm
@@ -236,7 +286,7 @@ public FormValidation doCheckName(@QueryParameter String name) {
         }
 
         @RequirePOST
-        public FormValidation doCheckDefaultVersion(@AncestorInPath Item context, @QueryParameter String defaultVersion, @QueryParameter boolean implicit, @QueryParameter boolean allowVersionOverride, @QueryParameter boolean allowBRANCH_NAME, @QueryParameter String name) {
+        public FormValidation doCheckDefaultVersion(@AncestorInPath Item context, @QueryParameter String defaultVersion, @QueryParameter boolean implicit, @QueryParameter boolean allowVersionOverride, @QueryParameter boolean allowBRANCH_NAME, @QueryParameter boolean allowBRANCH_NAME_PR, @QueryParameter String name) {
             if (defaultVersion.isEmpty()) {
                 if (implicit) {
                     return FormValidation.error("If you load a library implicitly, you must specify a default version.");
@@ -247,6 +297,9 @@ public FormValidation doCheckDefaultVersion(@AncestorInPath Item context, @Query
                 if (!allowVersionOverride) {
                     return FormValidation.error("If you deny overriding a default version, you must define that version.");
                 }
+                if (allowBRANCH_NAME_PR) {
+                    return FormValidation.warning("This setting has no effect when you do not allow use of literal '@${BRANCH_NAME}' for overriding a default version");
+                }
                 return FormValidation.ok();
             } else {
                 if ("${BRANCH_NAME}".equals(defaultVersion)) {

src/main/resources/org/jenkinsci/plugins/workflow/libs/LibraryConfiguration/config.jelly

@@ -40,6 +40,9 @@ THE SOFTWARE.
     <f:entry field="allowBRANCH_NAME" title="${%Allow literal use of @Library 'libname@$${BRANCH_NAME}' in pipeline scripts from SCM; falls back to default version if BRANCH_NAME is not available or not found}">
         <f:checkbox default="false"/>
     </f:entry>
+    <f:entry field="allowBRANCH_NAME_PR" title="${%If you allow literal use of @Library 'libname@$${BRANCH_NAME}' above, you can also allow fallback to CHANGE_BRANCH and/or CHANGE_TARGET for pull request builds}">
+        <f:checkbox default="false"/>
+    </f:entry>
     <f:entry field="includeInChangesets" title="${%Include @Library changes in job recent changes}">
         <f:checkbox default="true"/>
     </f:entry>

src/main/resources/org/jenkinsci/plugins/workflow/libs/LibraryConfiguration/help-allowBRANCH_NAME_PR.html

@@ -0,0 +1,10 @@
+<div>
+  If checked, and if scripts are allowed to select a custom version
+  of the library by appending literally <code>@${BRANCH_NAME}</code>
+  in the <code>@Library</code> annotation, then for pull request
+  builds additional fall-back library branches would include the
+  names used as <code>CHANGE_BRANCH</code> (name of source branch
+  of pipeline pull request) and <code>CHANGE_TARGET</code> (name
+  of target branch of pipeline pull request), if such branch names
+  already exist in the trusted shared library repository.
+</div>