[SourceKit/CodeFormat] Column-align multiple patterns in catch clauses.

Catch clauses now support mutliple patterns. Like 'case' patterns, these
should be column-aligned if split across multiple lines.

do {
  ...
} catch MyErr.a(let x),
        MyErr.b(let x) {
  print("hello")
}

Author: Nathan Hawes

lib/IDE/Formatting.cpp

@@ -1809,38 +1809,27 @@ class FormatWalker : public ASTWalker {
 
     auto *CS = dyn_cast<CaseStmt>(S);
     if (CS && CS->getParentKind() == CaseParentKind::Switch) {
-      if (TrailingTarget && !TrailingTarget->isEmpty())
-        return None;
-
       SourceLoc CaseLoc = CS->getLoc();
       if (!SM.isBeforeInBuffer(CaseLoc, TargetLocation))
         return None;
 
       SourceRange LabelItemsRange = CS->getLabelItemsRange();
       SourceLoc ColonLoc = getLocIfKind(SM, LabelItemsRange.End, tok::colon);
 
-      if (isTargetContext(CaseLoc, ColonLoc)) {
-        ListAligner Aligner(SM, TargetLocation, CaseLoc, CaseLoc, ColonLoc);
-        for (auto &Elem: CS->getCaseLabelItems()) {
-          SourceRange ElemRange = Elem.getSourceRange();
-          Aligner.updateAlignment(ElemRange, CS);
-          if (isTargetContext(ElemRange)) {
-            Aligner.setAlignmentIfNeeded(CtxOverride);
-            return IndentContext {
-              ElemRange.Start,
-              !OutdentChecker::hasOutdent(SM, ElemRange, CS)
-            };
-          }
-        }
-        return Aligner.getContextAndSetAlignment(CtxOverride);
-      }
-      if (ColonLoc.isValid() && isTargetContext(ColonLoc, SourceLoc())) {
+      if (auto Ctx = getIndentContextFromCaseItems(CS, /*CloseLoc=*/ColonLoc))
+        return Ctx;
+
+      if (ColonLoc.isValid() && isTargetContext(ColonLoc, SourceLoc()) &&
+          (!TrailingTarget || TrailingTarget->isEmpty())) {
         SourceRange ColonToEnd = SourceRange(ColonLoc, CS->getEndLoc());
         return IndentContext {
           CaseLoc,
           !OutdentChecker::hasOutdent(SM, ColonToEnd, CS)
         };
       }
+
+      if (TrailingTarget)
+        return None;
       return IndentContext {CaseLoc, false};
     }
 
@@ -1858,13 +1847,21 @@ class FormatWalker : public ASTWalker {
     }
 
     if (CS && CS->getParentKind() == CaseParentKind::DoCatch) {
-      if (auto *BS = dyn_cast<BraceStmt>(CS->getBody())) {
-        if (auto Ctx = getIndentContextFrom(BS, CS->getStartLoc()))
-          return Ctx;
-      }
+      SourceLoc CatchLoc = CS->getLoc();
+      SourceLoc L;
+
+      auto *BS = dyn_cast<BraceStmt>(CS->getBody());
+      if (BS) L = getLocIfKind(SM, BS->getLBraceLoc(), tok::l_brace);
+
+      if (auto Ctx = getIndentContextFromCaseItems(CS, /*CloseLoc=*/L))
+        return Ctx;
+
+      if (auto Ctx = getIndentContextFrom(BS, CS->getStartLoc()))
+        return Ctx;
+
       if (TrailingTarget)
         return None;
-      return IndentContext {CS->getStartLoc(), true};
+      return IndentContext {CatchLoc, false};
     }
 
     if (auto *IS = dyn_cast<IfStmt>(S)) {
@@ -2086,6 +2083,33 @@ class FormatWalker : public ASTWalker {
     return Bounds;
   }
 
+  Optional<IndentContext>
+  getIndentContextFromCaseItems(CaseStmt *CS, SourceLoc CloseLoc) {
+    SourceLoc IntroducerLoc = CS->getLoc();
+    if (!isTargetContext(IntroducerLoc, CloseLoc))
+      return None;
+
+    ListAligner Aligner(SM, TargetLocation, IntroducerLoc, IntroducerLoc,
+                        CloseLoc);
+    for (auto &Elem: CS->getCaseLabelItems()) {
+      // Skip the implicit 'error' pattern for empty catch CaseStmts.
+      if ((!Elem.getPattern() || Elem.getPattern()->isImplicit()) &&
+          Elem.getWhereLoc().isInvalid())
+        continue;
+
+      SourceRange ElemRange = Elem.getSourceRange();
+      Aligner.updateAlignment(ElemRange, CS);
+      if (isTargetContext(ElemRange)) {
+        Aligner.setAlignmentIfNeeded(CtxOverride);
+        return IndentContext {
+          ElemRange.Start,
+          !OutdentChecker::hasOutdent(SM, ElemRange, CS)
+        };
+      }
+    }
+    return Aligner.getContextAndSetAlignment(CtxOverride);
+  }
+
 #pragma mark Expression indent contexts
 
   Optional<IndentContext>

test/SourceKit/CodeFormat/indent-trailing/trailing-catch-item-comma.swift

@@ -0,0 +1,7 @@
+do {
+    print("hello")
+} catch MyErr.a(let code),
+        MyErr.b(let code),
+
+// RUN: %sourcekitd-test -req=format -line=5 -length=1 %s | %FileCheck --strict-whitespace %s
+// CHECK: key.sourcetext: "        "

test/SourceKit/CodeFormat/indent-trailing/trailing-catch-item-no-comma.swift

@@ -0,0 +1,7 @@
+do {
+    print("hello")
+} catch MyErr.a(let code),
+        MyErr.b(let code)
+
+// RUN: %sourcekitd-test -req=format -line=5 -length=1 %s | %FileCheck --strict-whitespace %s
+// CHECK: key.sourcetext: ""

test/swift-indent/basic.swift

@@ -939,3 +939,36 @@ IncrementedFirst++
     }++
     .baz()
 
+
+// Multiple patterns in catch should align exactly.
+
+do {
+    print("hello")
+} catch MyErr.a(let code, let message),
+        MyErr.b(
+            let code,
+            let message
+        ),
+        MyErr.c(let code, let message) {
+    print("ahhh!")
+}
+
+do {
+    throw MyErr.a
+} catch where foo == 0,
+        where bar == 1 {
+}
+
+do
+{
+    print("hello")
+}
+catch MyErr.a(let code, let message),
+      MyErr.b(
+        let code,
+        let message
+      ),
+      MyErr.c(let code, let message)
+{
+    print("ahhh!")
+}