This view works in PouchDB but why does it fail to sync with CouchDB?

Question

After some time developing an app with PouchDB I am now beginning my first attempts at syncing with a remote CouchDB instance. For now I am only syncing with the CouchDB provided by the installable OSX CouchDB app.

Documents appear to sync fine but I am having trouble with a particular view. I've checked it is valid JS and can't see an error.

I am storing each view in its own design document, which I read is a best practise.

So far I've tried:

Removing toLowerCase() (no reason really, just to check)
Moving the value emitted into its own variable

Other folk have had issues with view sync due to the use of modern JS features but I believe I've written mine with ES5, which I've read is what is required.

Here is the view definition code:

const ddoc = {
  _id: '_design/title-only',
  views: {
    'title-only': {
      map: function titleOnly(doc) {
        if (doc.type && doc.type === 'song' && doc.title) {
          emit(doc.title.toLowerCase(), {
            id: doc._id,
            title: doc.title,
            authors: doc.authors,
            starred: doc.starred || false,
            labels: doc.labels || [],
            createdAt: doc.createdAt,
          });
        }
      }.toString(),
    },
  }
};

I get an error of type "compilation_error".

Here is the error message:

"Compilation of the map function in the 'title-only' view failed: Expression does not eval to a function. (function titleOnly(doc) {
                                if (doc.type && doc.type === 'song' && doc.title) {
                                    emit(doc.title.toLowerCase(), {
                                        id: doc._id,
                                        title: doc.title,
                                        authors: doc.authors,
                                        starred: doc.starred || false,
                                        labels: doc.labels || [],
                                        createdAt: doc.createdAt,
                                    });
                                }
                            })"

Any pointers gratefully received, thanks.

Flimzy Flimzy · Accepted Answer · 2019-06-12T08:20:09

Don't use a named function.

In other words, replace this:

map: function titleOnly(doc) {

with this:

map: function(doc) {

This view works in PouchDB but why does it fail to sync with CouchDB?

1 Answers