What causes ""{uri}" already bound to the "{prefix}" prefix" in dianping/cat?

Keep one prefix per namespace URI and delete the redundant declaration.

dianping/cat · warning · StaticWarning

W02

W02

Error message

"{uri}" already bound to the "{prefix}" prefix

What it means

W02 is a StaticWarning that the same namespace URI is being bound again to a (new) prefix. After addNamespace() installs the new binding it checks whether a previous entry existed for that URI; if so it warns that the URI was already bound to the old prefix. Unlike XQST0047 this is not fatal — it just signals redundant or potentially confusing double binding.

Source

Thrown at cat-home/src/main/webapp/assets/js/editor/worker-xquery.js:1823

            }
            var namespace = this.getNamespace(uri);
            if (namespace && namespace.type === type && type !== 'declare' && !namespace.override) {
                throw new StaticError('XQST0047', '"' + uri + '": duplicate target namespace', pos);
            }
            namespace = this.getNamespaceByPrefix(prefix);
            if (namespace && !namespace.override) {
                throw new StaticError('XQST0033', '"' + prefix + '": namespace prefix already bound to "' + namespace.uri + '"', pos);
            }

            namespace = this.namespaces[uri];
            this.namespaces[uri] = {
                prefix: prefix,
                pos: pos,
                type: type
            };

            if (namespace) {
                throw new StaticWarning('W02', '"' + uri + '" already bound to the "' + namespace.prefix + '" prefix', pos);
            }

        },

        getNamespaces: function(){
            return this.root.namespaces;
        },
        
        getNamespace: function (uri) {
            var that = this;
            while (that) {
                var namespace = that.namespaces[uri];
                if (namespace) {
                    return namespace;
                }
                that = that.parent;
            }

View on GitHub (pinned to e815e74d4c)

Solutions

Keep one prefix per namespace URI and delete the redundant declaration.
If both prefixes are intentional aliases, accept the warning but document it to avoid reader confusion.
Search the prolog for the URI string to find all competing declarations.

Example fix

// before
declare namespace a = "http://example.org/mod";
declare namespace b = "http://example.org/mod";

// after
declare namespace a = "http://example.org/mod";

Defensive patterns

Strategy: validation

Validate before calling

// Detect the same URI bound under two prefixes
var byUri = {};
bindings.forEach(function(b) {
  if (byUri[b.uri] && byUri[b.uri] !== b.prefix) {
    warn(b.uri + ' already bound as ' + byUri[b.uri]);
  }
  byUri[b.uri] = b.prefix;
});

Try / catch

if (e.name === 'StaticWarning' && e.code === 'W02') {
  reportLint(e.pos, e.message);
}

Prevention

One URI, one prefix — enforce via code review or lint.
During prefix migrations, remove old declarations in the same change.

When it happens

Trigger: 'declare namespace a = "U";' then 'declare namespace b = "U";' — the second addNamespace call finds the existing namespaces[uri] entry and warns, having already overwritten the binding.

Common situations: Copy-pasted prologs that alias the same module twice; teams standardizing on a new prefix while old code still declares the old one; refactors that add a 'cleaner' prefix without removing the old declaration.

Related errors

AI-assisted analysis of dianping/cat@e815e74d4c (2026-08-14). Data as JSON: /api/errors/4d6b9ff6498136a9. Report an issue: GitHub.