Consistent precondition formatting

Our "Preconditions:" blocks are very useful to determine the input invariants,
but they are bit inconsistent throughout the codebase, which makes them harder
to read (particularly cases with 5+ conditions in a single paragraph).

I've reformatted all of the cases to fit in simple rules:

1. Cases with a single condition are placed on a single line.
2. Cases with multiple conditions are placed in a bulleted list.

This format has been added to the style guide.

I've also mentioned "Postconditions:", though those are much less frequently
used, and all uses already match this style.

PiperOrigin-RevId: 327687465

1 files changed, 9 insertions, 0 deletions

diff --git a/g3doc/style.md b/g3doc/style.md
index d10549fe9..8258b0233 100644
--- a/g3doc/style.md
+++ b/g3doc/style.md
@@ -46,6 +46,15 @@ protected.
 Each field or variable protected by a mutex should state as such in a comment on
 the field or variable declaration.
 
+### Function comments
+
+Functions with special entry conditions (e.g., a lock must be held) should state
+these conditions in a `Preconditions:` comment block. One condition per line;
+multiple conditions are specified with a bullet (`*`).
+
+Functions with notable exit conditions (e.g., a `Done` function must eventually
+be called by the caller) can similarly have a `Postconditions:` block.
+
 ### Unused returns
 
 Unused returns should be explicitly ignored with underscores. If there is a