Fix NPE on trait with implicit null

smithy-lang · Aug 22, 2023 · 898dc09 · 898dc09
1 parent 68d122e
commit 898dc09
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Showing 3 changed files with 42 additions and 17 deletions.
diff --git a/smithy-syntax/src/main/java/software/amazon/smithy/syntax/Formatter.java b/smithy-syntax/src/main/java/software/amazon/smithy/syntax/Formatter.java
@@ -365,23 +365,32 @@ private Doc visit(TreeCursor cursor) {
                                 })
                                 .build();
                     } else {
-                        // Check the inner trait node for hard line breaks rather than the wrapper.
-                        TreeCursor traitNode = cursor
-                                .getFirstChild(TreeType.TRAIT_NODE)
-                                .getFirstChild(TreeType.NODE_VALUE)
-                                .getFirstChild(); // The actual node value.
-                        return new BracketBuilder()
-                                .open(Doc.text("("))
-                                .close(Doc.text(")"))
-                                .extractChildren(cursor, traitNode, child -> {
-                                    if (child.getTree().getType() == TreeType.TRAIT_NODE) {
-                                        // Split WS and NODE_VALUE so that they appear on different lines.
-                                        return child.getChildrenByType(TreeType.NODE_VALUE, TreeType.WS).stream();
-                                    } else {
-                                        return Stream.empty();
-                                    }
-                                })
-                                .build();
+                        if (cursor.getFirstChild(TreeType.TRAIT_NODE) != null) {
+                            // Check the inner trait node for hard line breaks rather than the wrapper.
+                            TreeCursor traitNode = cursor
+                                    .getFirstChild(TreeType.TRAIT_NODE)
+                                    .getFirstChild(TreeType.NODE_VALUE)
+                                    .getFirstChild(); // The actual node value.
+                            return new BracketBuilder()
+                                    .open(Doc.text("("))
+                                    .close(Doc.text(")"))
+                                    .extractChildren(cursor, traitNode, child -> {
+                                        if (child.getTree().getType() == TreeType.TRAIT_NODE) {
+                                            // Split WS and NODE_VALUE so that they appear on different lines.
+                                            return child.getChildrenByType(TreeType.NODE_VALUE, TreeType.WS).stream();
+                                        } else {
+                                            return Stream.empty();
+                                        }
+                                    })
+                                    .build();
+                        } else {
+                            // If the trait node is empty, explicitly set it to `null`.
+                            return new BracketBuilder()
+                                    .open(Doc.text("("))
+                                    .close(Doc.text(")"))
+                                    .children(Stream.<Doc>builder().add(Doc.text("null")).build())
+                                    .build();
+                        }
                     }
                 }
 

diff --git a/...c/test/resources/software/amazon/smithy/syntax/formatter/null-trait-body.formatted.smithy b/...c/test/resources/software/amazon/smithy/syntax/formatter/null-trait-body.formatted.smithy
@@ -0,0 +1,8 @@
+$version: "2.0"
+
+namespace smithy.example
+
+structure Struct {
+    @default(null)
+    a: String
+}
diff --git a/...-syntax/src/test/resources/software/amazon/smithy/syntax/formatter/null-trait-body.smithy b/...-syntax/src/test/resources/software/amazon/smithy/syntax/formatter/null-trait-body.smithy
@@ -0,0 +1,8 @@
+$version: "2.0"
+
+namespace smithy.example
+
+structure Struct {
+    @default()
+    a: String
+}