Check branch labels upon v2 dataset JSON validation

If a default branch label is set in the JSON then ensure it is defined on at least one node in the tree. We allow the special case of setting the default label to `none`. Note that `augur export` currently only exports clade and/or aa labels, but we should still be able to validate JSONs made somewhere else.

A test build is added.

augur/data/schema-export-v2.json

@@ -224,8 +224,7 @@
                         },
                         "branch_label": {
                             "description": "What branch label should be displayed by default.",
-                            "type": "string",
-                            "enum": ["clade", "aa", "none"]
+                            "type": "string"
                         }
                     }
                 },

augur/validate_export.py

@@ -57,6 +57,14 @@ def recurse(node):
     genes -= {"nuc"}
     return genes
 
+def collectBranchLabels(root):
+    labels = set()
+    def recurse(node):
+        labels.update(node.get("branch_attrs", {}).get("labels", {}).keys())
+        if "children" in node:
+            [recurse(child) for child in node["children"]]
+    recurse(root)
+    return labels
 
 def verifyMainJSONIsInternallyConsistent(data, ValidateError):
     """
@@ -144,6 +152,12 @@ def warn(msg):
                 if gene not in data["meta"]["genome_annotations"]:
                     warn("The tree defined mutations on gene {} which doesn't appear in the metadata annotations object.".format(gene))
 
+    default_branch_label = data.get("meta").get("display_defaults", {}).get("branch_label")
+    if default_branch_label and default_branch_label.lower() != "none":
+        labels = collectBranchLabels(data['tree'])
+        if not default_branch_label in labels:
+            warn("Default label to display \"{}\" isn't found anywhere on the tree!".format(default_branch_label))
+
     if not warnings:
         print("Validation succeeded")
     else:

tests/builds/validation/Snakefile

@@ -0,0 +1,5 @@
+rule all:
+  shell:
+    """
+    augur validate export-v2 auspice/v2_zika.json
+    """