The dynamic writer (Schema Sources: Schema from Schema Feature) would not write the first feature into the destination dataset, if it has an attribute called "fme_schema_handling" with the value "schema_only", which the schema feature output from the <Schema> port contains.

I don't think you need to use the FeatureMerger. You can just send the schema feature and data features to the writer feature type separately.

Problem solved. Thanks a lot.

Hello,

I just fell into the same error (with FME 2021.2), removing the Feature Merger doesn't work (northing is written). I had to sample every first row (I was writting several files with the fanout), then (re)-sort them to make sure the first row of each file is the double created, so I write them all.

Can you show us screenshots, including entire workflow and the dynamic writer feature type parameters dialog?

I can't show you the entire workflow (too big), but I can show you the part of interest :

On the left upper part is the dynamic reader, on left down part is the data I want to write.

The red box is the patch I had to create.

My data is previously ordered by, so when I use the sampler the parameters sets make sure it is the first one that I duplicate :

Then I sort them again (because I don't know if all the duplicates are written at the end or "at the right place I want them to be")

I remove an attribute that just serves me for the ordering process.

And the dynamic settings (for the writer) is pretty basic :

I just start writing at the 10th line in the excel, the rest is not changed.

I hope this helps you !

Thank you for your clarification.

I suppose that you intend to configure the destination schema based on the schema definition (i.e. attribute{} list) contained by the feature read by the FeatureReader (Schema port).

If I understand your intention correctly, you can do that with just removing "fme_schema_handling" attribute from the schema feature. And then, it's not necessary to sample the first feature any longer. 

The workflow should look like this.

See here to learn more.

Dynamic Workflows: Destination Schema is Derived from a Schema Feature

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I think this method can also be applied​ in your case, since you retrieve the schema definition from an external dataset with the FeatureReader.

Dynamic Workflows: Destination Schema is Derived from an External Dataset

Thank you so much for your answer, I had several FME script to modify because of this issue. Your solution is way faster and easier (and it works of course).

You made my day !