fix #8242, fix #12586: fix 'formatFloat' with 'precision = 0' (#12592)

* fix #8242, fix #12586: fix 'formatFloat' with 'precision = 0'

'formatFloat' with 'precision = 0' now gives the same result
(a number without a decimal point) in all backends.
This is compatible with Python's formatters, too.

* fix failing tests

* add changelog entry

* add version switch

changelog.md

@@ -7,29 +7,47 @@
 
 ### Breaking changes in the standard library
 
-- `base64.encode` no longer supports `lineLen` and `newLine` use `base64.encodeMIME` instead.
-- `os.splitPath()` behavior synchronized with `os.splitFile()` to return "/" as the dir component of "/root_sub_dir" instead of the empty string.
-- `sequtils.zip` now returns a sequence of anonymous tuples i.e. those tuples now do not have fields named "a" and "b".
+- `base64.encode` no longer supports `lineLen` and `newLine`.
+  Use `base64.encodeMIME` instead.
+- `os.splitPath()` behavior synchronized with `os.splitFile()` to return "/"
+   as the dir component of "/root_sub_dir" instead of the empty string.
+- `sequtils.zip` now returns a sequence of anonymous tuples i.e. those tuples
+  now do not have fields named "a" and "b".
+- `strutils.formatFloat` with `precision = 0` has the same behavior in all
+  backends, and it is compatible with Python's behavior,
+  e.g. `formatFloat(3.14159, precision = 0)` is now `3`, not `3.`.
+
 
 ### Breaking changes in the compiler
 
-- Implicit conversions for `const` behave correctly now, meaning that code like `const SOMECONST = 0.int; procThatTakesInt32(SOMECONST)` will be illegal now.
+- Implicit conversions for `const` behave correctly now, meaning that code like
+  `const SOMECONST = 0.int; procThatTakesInt32(SOMECONST)` will be illegal now.
   Simply write `const SOMECONST = 0` instead.
 
 
+
 ## Library additions
 
 - `macros.newLit` now works for ref object types.
 - `system.writeFile` has been overloaded to also support `openarray[byte]`.
-- Added overloaded `strformat.fmt` macro that use specified characters as delimiter instead of '{' and '}'.
+- Added overloaded `strformat.fmt` macro that use specified characters as
+  delimiter instead of '{' and '}'.
+
+
 
 ## Library changes
 
-- `asyncdispatch.drain` now properly takes into account `selector.hasPendingOperations` and only returns once all pending async operations are guaranteed to have completed.
-- `asyncdispatch.drain` now consistently uses the passed timeout value for all iterations of the event loop, and not just the first iteration. This is more consistent with the other asyncdispatch apis, and allows `asyncdispatch.drain` to be more efficient.
+- `asyncdispatch.drain` now properly takes into account `selector.hasPendingOperations`
+  and only returns once all pending async operations are guaranteed to have completed.
+- `asyncdispatch.drain` now consistently uses the passed timeout value for all
+  iterations of the event loop, and not just the first iteration.
+  This is more consistent with the other asyncdispatch apis, and allows
+  `asyncdispatch.drain` to be more efficient.
 - `base64.encode` and `base64.decode` was made faster by about 50%.
 - `htmlgen` adds [MathML](https://wikipedia.org/wiki/MathML) support (ISO 40314).
 
+
+
 ## Language additions
 
 
@@ -45,9 +63,12 @@
 
 ### Compiler changes
 
-- JS target indent is all spaces, instead of mixed spaces and tabs, for generated JavaScript.
+- JS target indent is all spaces, instead of mixed spaces and tabs, for
+  generated JavaScript.
+
 
 
 ## Bugfixes
 
-- The `FD` variant of `selector.unregister` for `ioselector_epoll` and `ioselector_select` now properly handle the `Event.User` select event type.
+- The `FD` variant of `selector.unregister` for `ioselector_epoll` and
+  `ioselector_select` now properly handle the `Event.User` select event type.