unison/unison-src/transcripts/doc-formatting.md

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This transcript explains a few minor details about doc parsing and pretty-printing, both from a user point of view and with some implementation notes. The later stuff is meant more as unit testing than for human consumption. (The ucm `add` commands and their output are hidden for brevity.)
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Docs can be used as inline code comments.
```ucm:hide
scratch/main> builtins.merge
```
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```unison
foo : Nat -> Nat
foo n =
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_ = [: do the thing :]
n + 1
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```
```ucm:hide
scratch/main> add
```
```ucm
scratch/main> view foo
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```
Note that `@` and `:]` must be escaped within docs.
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```unison
escaping = [: Docs look [: like \@this \:] :]
```
```ucm:hide
scratch/main> add
```
```ucm
scratch/main> view escaping
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```
(Alas you can't have `\@` or `\:]` in your doc, as there's currently no way to 'unescape' them.)
```unison
-- Note that -- comments are preserved within doc literals.
commented = [:
example:
-- a comment
f x = x + 1
:]
```
```ucm:hide
scratch/main> add
```
```ucm
scratch/main> view commented
```
### Indenting, and paragraph reflow
Handling of indenting in docs between the parser and pretty-printer is a bit fiddly.
```unison
-- The leading and trailing spaces are stripped from the stored Doc by the
-- lexer, and one leading and trailing space is inserted again on view/edit
-- by the pretty-printer.
doc1 = [: hi :]
```
```ucm:hide
scratch/main> add
```
```ucm
scratch/main> view doc1
```
```unison
-- Lines (apart from the first line, i.e. the bit between the [: and the
-- first newline) are unindented until at least one of
-- them hits the left margin (by a post-processing step in the parser).
-- You may not notice this because the pretty-printer indents them again on
-- view/edit.
doc2 = [: hello
- foo
- bar
and the rest. :]
```
```ucm:hide
scratch/main> add
```
```ucm
scratch/main> view doc2
```
```unison
doc3 = [: When Unison identifies a paragraph, it removes any newlines from it before storing it, and then reflows the paragraph text to fit the display window on display/view/edit.
For these purposes, a paragraph is any sequence of non-empty lines that have zero indent (after the unindenting mentioned above.)
- So this is not a paragraph, even
though you might want it to be.
And this text | as a paragraph
is not treated | either.
Note that because of the special treatment of the first line mentioned above, where its leading space is removed, it is always treated as a paragraph.
:]
```
```ucm:hide
scratch/main> add
```
```ucm
scratch/main> view doc3
```
```unison
doc4 = [: Here's another example of some paragraphs.
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All these lines have zero indent.
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- Apart from this one. :]
```
```ucm:hide
scratch/main> add
```
```ucm
scratch/main> view doc4
```
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```unison
-- The special treatment of the first line does mean that the following
-- is pretty-printed not so prettily. To fix that we'd need to get the
-- lexer to help out with interpreting doc literal indentation (because
-- it knows what columns the `[:` was in.)
doc5 = [: - foo
- bar
and the rest. :]
```
```ucm:hide
scratch/main> add
```
```ucm
scratch/main> view doc5
```
```unison
-- You can do the following to avoid that problem.
doc6 = [:
- foo
- bar
and the rest.
:]
```
```ucm:hide
scratch/main> add
```
```ucm
scratch/main> view doc6
```
### More testing
```unison
-- Check empty doc works.
empty = [::]
expr = foo 1
```
```ucm:hide
scratch/main> add
```
```ucm
scratch/main> view empty
```
```unison
test1 = [:
The internal logic starts to get hairy when you use the \@ features, for example referencing a name like @List.take. Internally, the text between each such usage is its own blob (blob ends here --> @List.take), so paragraph reflow has to be aware of multiple blobs to do paragraph reflow (or, more accurately, to do the normalization step where newlines with a paragraph are removed.)
Para to reflow: lorem ipsum dolor lorem ipsum dolor lorem ipsum dolor lorem ipsum dolor lorem ipsum dolor lorem ipsum dolor lorem ipsum dolor ending in ref @List.take
@List.take starting para lorem ipsum dolor lorem ipsum dolor lorem ipsum dolor lorem ipsum dolor lorem ipsum dolor lorem ipsum dolor lorem ipsum dolor.
Middle of para: lorem ipsum dolor lorem ipsum dolor lorem ipsum dolor @List.take lorem ipsum dolor lorem ipsum dolor lorem ipsum dolor lorem ipsum dolor.
- non-para line (@List.take) with ref @List.take
Another non-para line
@List.take starting non-para line
- non-para line with ref @List.take
before a para-line lorem ipsum dolor lorem ipsum dolor lorem ipsum dolor lorem ipsum dolor lorem ipsum dolor lorem ipsum dolor lorem ipsum dolor lorem ipsum dolor.
- non-para line followed by a para line starting with ref
@List.take lorem ipsum dolor lorem ipsum dolor lorem ipsum dolor lorem ipsum dolor lorem ipsum dolor lorem ipsum dolor lorem ipsum dolor lorem ipsum dolor.
a para-line ending with ref lorem ipsum dolor lorem ipsum dolor lorem ipsum dolor lorem ipsum dolor lorem ipsum dolor lorem ipsum dolor lorem ipsum dolor lorem ipsum dolor @List.take
- non-para line
para line lorem ipsum dolor lorem ipsum dolor lorem ipsum dolor lorem ipsum dolor lorem ipsum dolor lorem ipsum dolor lorem ipsum dolor lorem ipsum dolor
@List.take followed by non-para line starting with ref.
@[signature] List.take
@[source] foo
@[evaluate] expr
@[include] doc1
-- note the leading space below
@[signature] List.take
:]
```
```ucm:hide
scratch/main> add
```
```ucm
scratch/main> view test1
```
```unison
-- Regression test for #1363 - preservation of spaces after @ directives in first line when unindenting
reg1363 = [: `@List.take foo` bar
baz :]
```
```ucm:hide
scratch/main> add
```
```ucm
scratch/main> view reg1363
```
```unison
-- Demonstrate doc display when whitespace follows a @[source] or @[evaluate]
-- whose output spans multiple lines.
test2 = [:
Take a look at this:
@[source] foo ▶ bar
:]
```
```ucm:hide
scratch/main> add
```
View is fine.
```ucm
scratch/main> view test2
```
But note it's not obvious how display should best be handling this. At the moment it just does the simplest thing:
```ucm
scratch/main> display test2
```