V2 notes

doc/v2.md

@@ -0,0 +1,118 @@
+# JD V2
+
+## What should before and after context look like for nested lists?
+
+- need context for producing minimal diffs
+- so we can insert an element into the middle of a list
+- patch must apply only once so we need to add enough context
+
+A:
+
+```json
+[[1,2,3],[4,6],[7,8,9]]
+
+```
+
+B:
+
+```json
+[[1,2,3],[4,5,6],[7,8,9]]
+```
+
+D:
+
+```diff
+@ [1,1]
+ 4
++ 5
+ 6
+```
+
+- the `4` and `6` are compared for equality
+- no context means "end of list" or "beginning of list"
+
+A:
+
+```json
+[2,3]
+```
+
+B:
+
+```json
+[1,2,3]
+```
+
+D:
+
+```diff
+@ [0]
++ 1
+ 2
+```
+
+- if a patch doesn't have enough context to prevent double application, more context is added
+
+A:
+
+```json
+[1,2,2,3]
+```
+
+B:
+
+```json
+[1,2,2,2,3]
+```
+
+D:
+
+```diff
+@ [2]
+ 2
++ 2
+ 2
+ 3
+```
+
+- the `3` prevents double application
+
+## What should metadata look like?
+
+- metadata applying to entire hunk (not just path) is a separate line
+- version (2)
+- merge patch behavior
+
+```diff
+^ {"version":"2"}
+@ ["foo"]
+- "bar"
++ "baz"
+```
+
+```diff
+^ {"version":2,"merge":true}
+@ ["foo"]
+- "bar"
++ "baz"
+```
+
+## What about in-path metadata?
+
+- no more metadata in a list (`[["multiset"],{}]`)
+- still objects mean set
+- object in list means multiset
+- object with keys means object identity
+- other use cases are now in the top-level `^` metadata object
+
+Set:
+
+```diff
+@ ["foo",{"id":"bar"}]
+```
+
+Multiset:
+
+```diff
+@ ["foo",[{"id":"bar"}]]
+```