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Rewrite trailing setters and field setters as mapper.rebuild() chains #153

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Merged
steve-aom-elliott merged 2 commits into from
Jul 3, 2026
Merged

Rewrite trailing setters and field setters as mapper.rebuild() chains #153

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9a7bec6
Rewrite trailing setters and field setters as mapper.rebuild() chains
steve-aom-elliott Jul 3, 2026
db9c799
Remove verbose comments
steve-aom-elliott Jul 3, 2026
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216 changes: 214 additions & 2 deletions src/main/java/org/openrewrite/java/jackson/MigrateMapperSettersToBuilder.java
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Original file line number Diff line number Diff line change
Expand Up @@ -184,6 +184,7 @@ public J visitBlock(J.Block block, ExecutionContext ctx) {
if (visited != block) {
doAfterVisit(new UpdateSerializationInclusionConfiguration().getVisitor());
doAfterVisit(new UpdateAutoDetectVisibilityConfiguration().getVisitor());
doAfterVisit(coalesceRebuildAssignments());
}
return visited;
}
Expand Down Expand Up @@ -276,11 +277,14 @@ public J visitNewClass(J.NewClass newClass, ExecutionContext ctx) {
}
}

if (!(mi.getSelect() instanceof J.Identifier)) {
Expression select = mi.getSelect();
if (!(select instanceof J.Identifier) &&
!(select instanceof J.FieldAccess &&
((J.FieldAccess) select).getTarget() instanceof J.Identifier)) {
return mi;
}

String matchedMapper = matchingMapperType(mi.getSelect().getType());
String matchedMapper = matchingMapperType(select.getType());
if (matchedMapper == null) {
return mi;
}
Expand All @@ -290,6 +294,13 @@ public J visitNewClass(J.NewClass newClass, ExecutionContext ctx) {
return mi;
}

if (isTopLevelStatement(getCursor()) && isReassignableReceiver(select, getCursor())) {
J rebuilt = rewriteAsRebuildAssignment(mi, select, matchedMapper, mapping, ctx);
if (rebuilt != null) {
return rebuilt;
}
}

// Not eligible for builder migration - add a TODO comment
String simpleMapperName = matchedMapper.substring(matchedMapper.lastIndexOf('.') + 1);
String commentText = String.format(
Expand Down Expand Up @@ -696,10 +707,210 @@ private J applyBuilderTemplate(String mapperFqn, List<J.MethodInvocation> setter
}
return chained;
}

private @Nullable J rewriteAsRebuildAssignment(J.MethodInvocation mi, Expression select,
String mapperFqn, SetterToBuilderMapping mapping,
ExecutionContext ctx) {
String builderName = mapping.builderName;
if (mapping == SetterToBuilderMapping.SET_DEFAULT_PROPERTY_INCLUSION &&
mi.getArguments().size() == 1 &&
!(mi.getArguments().get(0) instanceof J.Empty) &&
TypeUtils.isAssignableTo("com.fasterxml.jackson.annotation.JsonInclude$Include",
mi.getArguments().get(0).getType())) {
builderName = "serializationInclusion";
}
StringBuilder templateCode = new StringBuilder();
templateCode.append("#{any(").append(mapperFqn).append(")} = #{any(")
.append(mapperFqn).append(")}.rebuild()\n.").append(builderName).append("(");
List<Expression> templateArgs = new ArrayList<>();
templateArgs.add(select);
templateArgs.add(select);
boolean first = true;
for (Expression arg : mi.getArguments()) {
if (arg instanceof J.Empty) {
continue;
}
if (!first) {
templateCode.append(", ");
}
first = false;
templateCode.append("#{any()}");
templateArgs.add(arg);
}
templateCode.append(")\n.build()");

maybeAddImport(mapperFqn);
maybeAddImport(JSON_INCLUDE);

JavaParser.Builder<?, ?> parser = JavaParser.fromJavaVersion()
.classpathFromResources(ctx, "jackson-annotations-2", "jackson-core-2", "jackson-databind-2")
.dependsOn(mapperStub(mapperFqn, emptyList()));

return JavaTemplate.builder(templateCode.toString())
.imports(mapperFqn, JSON_INCLUDE)
.javaParser(parser)
.build()
.apply(getCursor(), mi.getCoordinates().replace(), templateArgs.toArray());
}
}
);
}

private static boolean isTopLevelStatement(Cursor cursor) {
return cursor.getParentTreeCursor().getValue() instanceof J.Block;
}

private static boolean isReassignableReceiver(Expression select, Cursor cursor) {
if (select instanceof J.Identifier) {
return isReassignableLocal((J.Identifier) select, cursor);
}
if (select instanceof J.FieldAccess) {
J.FieldAccess fa = (J.FieldAccess) select;
if (!(fa.getTarget() instanceof J.Identifier)) {
return false;
}
JavaType.Variable v = fa.getName().getFieldType();
return v != null && !v.hasFlags(Flag.Final);
}
return false;
}

private static boolean isReassignableLocal(J.Identifier ident, Cursor cursor) {
JavaType.Variable fieldType = ident.getFieldType();
if (fieldType != null && fieldType.hasFlags(Flag.Final)) {
return false;
Comment on lines +763 to +781

@sambsnyd sambsnyd Jul 3, 2026

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I wonder if we should have a Reassignable trait or something like it. There must be quite a few recipes which must ask a variation on this question.

@steve-aom-elliott steve-aom-elliott Jul 3, 2026

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I can kick something off to try making one that would live in openrewrite/rewrite, as I feel that's likely a more appropriate place for it to live. Later on we could refactor this to use that trait instead?

@steve-aom-elliott steve-aom-elliott Jul 3, 2026

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@sambsnyd You can see the initial pass of this here:

}
String name = ident.getSimpleName();
Cursor c = cursor;
while (c != null) {
Object v = c.getValue();
if (v instanceof J.Block) {
for (Statement stmt : ((J.Block) v).getStatements()) {
J.VariableDeclarations vd = extractVariableDeclarations(stmt);
if (vd == null) {
continue;
}
for (J.VariableDeclarations.NamedVariable nv : vd.getVariables()) {
if (name.equals(nv.getName().getSimpleName()) &&
TypeUtils.isOfType(nv.getName().getType(), ident.getType())) {
return !vd.hasModifier(J.Modifier.Type.Final);
}
}
}
}
if (v instanceof J.MethodDeclaration) {
for (Statement p : ((J.MethodDeclaration) v).getParameters()) {
if (p instanceof J.VariableDeclarations) {
for (J.VariableDeclarations.NamedVariable nv : ((J.VariableDeclarations) p).getVariables()) {
if (name.equals(nv.getName().getSimpleName())) {
return false;
}
}
}
}
return false;
}
c = c.getParent();
}
return false;
}

private static JavaIsoVisitor<ExecutionContext> coalesceRebuildAssignments() {
return new JavaIsoVisitor<ExecutionContext>() {
@Override
public J.Block visitBlock(J.Block block, ExecutionContext ctx) {
J.Block b = super.visitBlock(block, ctx);
List<Statement> stmts = b.getStatements();
if (stmts.size() < 2) {
return b;
}
List<Statement> merged = new ArrayList<>(stmts.size());
boolean changed = false;
int i = 0;
while (i < stmts.size()) {
RebuildParts head = tryParseRebuildAssignment(stmts.get(i));
if (head == null) {
merged.add(stmts.get(i));
i++;
continue;
}
List<J.MethodInvocation> allChainCalls = new ArrayList<>(head.chainCalls);
int j = i + 1;
while (j < stmts.size()) {
RebuildParts next = tryParseRebuildAssignment(stmts.get(j));
if (next == null || !SemanticallyEqual.areEqual(head.lhs, next.lhs)) {
break;
}
allChainCalls.addAll(next.chainCalls);
j++;
}
if (j == i + 1) {
merged.add(stmts.get(i));
i++;
continue;
}
Statement coalesced = rebuildCoalescedAssignment(head, allChainCalls);
merged.add(coalesced);
changed = true;
i = j;
}
return changed ? b.withStatements(merged) : b;
}
};
}

private static class RebuildParts {
final J.Assignment assignment;
final Expression lhs;
final J.MethodInvocation buildCall;
final J.MethodInvocation rebuildCall;
final List<J.MethodInvocation> chainCalls;

RebuildParts(J.Assignment assignment, Expression lhs, J.MethodInvocation buildCall,
J.MethodInvocation rebuildCall, List<J.MethodInvocation> chainCalls) {
this.assignment = assignment;
this.lhs = lhs;
this.buildCall = buildCall;
this.rebuildCall = rebuildCall;
this.chainCalls = chainCalls;
}
}

private static @Nullable RebuildParts tryParseRebuildAssignment(Statement stmt) {
if (!(stmt instanceof J.Assignment)) {
return null;
}
J.Assignment assignment = (J.Assignment) stmt;
if (!(assignment.getAssignment() instanceof J.MethodInvocation)) {
return null;
}
J.MethodInvocation buildCall = (J.MethodInvocation) assignment.getAssignment();
if (!"build".equals(buildCall.getName().getSimpleName())) {
return null;
}
List<J.MethodInvocation> chainCalls = new ArrayList<>();
Expression current = buildCall.getSelect();
while (current instanceof J.MethodInvocation) {
J.MethodInvocation mi = (J.MethodInvocation) current;
if ("rebuild".equals(mi.getName().getSimpleName())) {
Collections.reverse(chainCalls);
return new RebuildParts(assignment, assignment.getVariable(), buildCall, mi, chainCalls);
}
chainCalls.add(mi);
current = mi.getSelect();
}
return null;
}

private static Statement rebuildCoalescedAssignment(RebuildParts head, List<J.MethodInvocation> allChainCalls) {
Expression newSelect = head.rebuildCall;
for (J.MethodInvocation chainCall : allChainCalls) {
newSelect = chainCall.withSelect(newSelect);
}
J.MethodInvocation newBuild = head.buildCall.withSelect(newSelect);
return head.assignment.withAssignment(newBuild);
}

/**
* Returns the FQN of the mapper type matched by the given new class, or null if none match.
*/
Expand Down Expand Up @@ -822,6 +1033,7 @@ private static String mapperStub(String mapperFqn, List<J.MethodInvocation> unkn
.append(" extends com.fasterxml.jackson.databind.ObjectMapper {\n");
sb.append(" public ").append(simpleName).append("() {}\n");
sb.append(" public static Builder builder() { return null; }\n");
sb.append(" public Builder rebuild() { return null; }\n");
sb.append(" public static class Builder extends ")
.append("com.fasterxml.jackson.databind.cfg.MapperBuilder<")
.append(simpleName).append(", Builder> {\n");
Expand Down
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