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RFC: Restrict fields to a single line (revision 1)

This RFC seeks to establish that regular Field elements can never contain line breaks (\n) by repurposing the current newline continuation operator for new functionality.

The two changes

1. |, the current newline continuation operator, becomes the direct line continuation operator

Currently the newline continuation operator exists and works like this:

> my_field contains a value of "First line\nSecond line"

my_field: First line
|         Second line

According to this proposal | becomes the direct lined continuation operator and works like this:

> my_field contains a value of "my-token-continued-wihout-gap"

my_field: my-token-
|         continued-wihout-gap

2. \ retains its current functionality but adopts a new name: the spaced line continuation operator

The functionality remains unchanged:

> my_field contains a value of "my value continued with gap"

my_field: my value
\         continued with gap

Design considerations

Considerations around conveying meaning through document structure

An integral part of the reasoning behind this RFC is to establish a predictable dichotomy of single line data versus multi line data, a concept that is firmly established and known to the likely widest technological user base there can be: people who use a browser (in the form of the single line text input and the multi line textarea). By guaranteeing that fields only ever contain a single line the nature of data to be supplied becomes much more intuitively clear to users, and although a savvy user might still try to change a field into a block then, the barrier to such misuse and potential ensuing errors is considerably higher.

Cultural bias considerations

This RFC also exists because the initial specification (which only offers one way to continue a line - separated by a space) neglects that in some cultures a line continuation that does not introduce an extra space might be customary instead.

(Thanks to Tomoki Aonuma for pointing this out - see

Relation to Multiline Field Terminology RFC

This RFC relates to the changes proposed in If a Field only ever contains a single line, the therein proposed Multline Field terminology complements that behavior on the descriptive side as well. (On the functional side the existing Block element already complements the herein described single-line only field).

What is (not) lost, what is gained

In early eno language drafts there were only line continuations, mostly to allow this:

my_command: foo -u alice
\               -p 1234567890

Additional newline continuations were introduced to allow this:

| foo -u alice
\     -p 1234567890
| foo -u bob
\     -p abcdefghijklmnopqrstuvwxyz

But this can be stored (even more semantically I would argue) as a list too:

- foo -u alice
\     -p 1234567890
- foo -u bob
\     -p abcdefghijklmnopqrstuvwxyz

And based on this RFC we actually gain new possibilities:

|                                                &options=compact,files
|                                                &page=3
|                                                &lang=fr

| tQpVvLtVrOAQKJusuehMorHqvNOVmTrLPvVVEfMGeiSdfXQWdDgpGMhfQwc
| WprgefVgAgRhaOivsTvLDOwxIndAtpspeEmmsbkfrlsKIGVgrMegbCGtSWC
| xtHYYVBMfYsKdhyBAdyyiwdttoyLBUzwZLSNYnwPhkSYdaVUPldOwzeygiA

Continuation behavior details

There are some not so obvious scenarios and edge cases to consider here - the 4 following examples should completely cover these ambiguities. If you spot an oversight or something is yet unclear you're very welcome to open an issue to bring it up - thank you!

1. There is no leading/trailing spacing

\ value

> results in 'value' (leading/trailing spacing is discarded)

2. The spacing produced by spaced line continuations does not accumulate

\ value
\ continued

> results in 'value continued' (*one* separating space only)

3. Empty spaced line continuations between direct line continuations are taken into account

| value
| continued

> results in 'value continued'

4. Multiple empty spaced line continuation between direct line continuations do not accumulate

| value
| continued

> results in 'value continued' (*one* separating space only)

Revision history

rev1: Added a section to clarify continuation behavior details and edge case scenarios

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