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changelog.md

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v2.0.0 - yyyy-mm-dd

Changes affecting backward compatibility

  • httpclient.contentLength default to -1 if the Content-Length header is not set in the response, it followed Apache HttpClient(Java), http(go) and .Net HttpWebResponse(C#) behavior. Previously it raised ValueError.

  • addr is now available for all addressable locations, unsafeAddr is now deprecated and an alias for addr.

  • Certain definitions from the default system module have been moved to the following new modules:

    • std/syncio
    • std/assertions
    • std/formatfloat
    • std/objectdollar
    • std/widestrs
    • std/typedthreads
    • std/sysatomics

In the future, these definitions will be removed from the system module, and their respective modules will have to be imported to use them. Currently, to make these imports required, the -d:nimPreviewSlimSystem option may be used.

  • Enabling -d:nimPreviewSlimSystem also removes the following deprecated symbols in the system module:

    • Aliases with Error suffix to exception types that have a Defect suffix (see exceptions): ArithmeticError, DivByZeroError, OverflowError, AccessViolationError, AssertionError, OutOfMemError, IndexError, FieldError, RangeError, StackOverflowError, ReraiseError, ObjectAssignmentError, ObjectConversionError, FloatingPointError, FloatOverflowError, FloatUnderflowError, FloatInexactError, DeadThreadError, NilAccessError
    • addQuitProc, replaced by exitprocs.addExitProc
    • Legacy unsigned conversion operations: ze, ze64, toU8, toU16, toU32
    • TaintedString, formerly a distinct alias to string
    • PInt32, PInt64, PFloat32, PFloat64, aliases to ptr int32, ptr int64, ptr float32, ptr float64

  • Enabling -d:nimPreviewSlimSystem removes the import of channels_builtin in in the system module.

  • Enabling -d:nimPreviewCstringConversion, ptr char, ptr array[N, char] and ptr UncheckedArray[N, char] don't support conversion to cstring anymore.

  • The gc:v2 option is removed.

  • The mainmodule and m options are removed.

  • The threads:on option is now the default.

  • Optional parameters in combination with : body syntax (RFC #405) are now opt-in via experimental:flexibleOptionalParams.

  • Automatic dereferencing (experimental feature) is removed.

  • The Math.trunc polyfill for targeting Internet Explorer was previously included in most JavaScript output files. Now, it is only included with -d:nimJsMathTruncPolyfill. If you are targeting Internet Explorer, you may choose to enable this option or define your own Math.trunc polyfill using the emit pragma. Nim uses Math.trunc for the division and modulo operators for integers.

  • shallowCopy and shallow are removed for ARC/ORC. Use move when possible or combine assignment and sink for optimization purposes.

  • The nimPreviewDotLikeOps define is going to be removed or deprecated.

  • The {.this.} pragma, deprecated since 0.19, has been removed.

  • nil literals can no longer be directly assigned to variables or fields of distinct pointer types. They must be converted instead. ```nim type Foo = distinct ptr int

# Before: var x: Foo = nil # After: var x: Foo = Foo(nil)

- Removed two type pragma syntaxes deprecated since 0.20, namely
  `type Foo = object {.final.}`, and `type Foo {.final.} [T] = object`.

- `foo a = b` now means `foo(a = b)` rather than `foo(a) = b`. This is consistent
  with the existing behavior of `foo a, b = c` meaning `foo(a, b = c)`.
  This decision was made with the assumption that the old syntax was used rarely;
  if your code used the old syntax, please be aware of this change.

- [Overloadable enums](https://nim-lang.github.io/Nim/manual.html#overloadable-enum-value-names) and Unicode Operators
  are no longer experimental.

- Removed the `nimIncrSeqV3` define.

- `macros.getImpl` for `const` symbols now returns the full definition node
  (as `nnkConstDef`) rather than the AST of the constant value.

- Lock levels are deprecated, now a noop.

- ORC is now the default memory management strategy. Use
  `--mm:refc` for a transition period.

- `strictEffects` are no longer experimental.
  Use `legacy:laxEffects` to keep backward compatibility.

- The `gorge`/`staticExec` calls will now return a descriptive message in the output
  if the execution fails for whatever reason. To get back legacy behaviour use `-d:nimLegacyGorgeErrors`.

- Pointer to `cstring` conversion now triggers a `[PtrToCstringConv]` warning.
  This warning will become an error in future versions! Use a `cast` operation
  like `cast[cstring](x)` instead.

- `logging` will default to flushing all log level messages. To get the legacy behaviour of only flushing Error and Fatal messages, use `-d:nimV1LogFlushBehavior`.

- Object fields now support default values, see https://nim-lang.github.io/Nim/manual.html#types-default-values-for-object-fields for details.

- Redefining templates with the same signature was previously
  allowed to support certain macro code. To do this explicitly, the
  `{.redefine.}` pragma has been added. Note that this is only for templates.
  Implicit redefinition of templates is now deprecated and will give an error in the future.

- Using an unnamed break in a block is deprecated. This warning will become an error in future versions! Use a named block with a named break instead.

- Several Standard libraries are moved to nimble packages, use `nimble` to install them:
  - `std/punycode` => `punycode`
  - `std/asyncftpclient` => `asyncftpclient`
  - `std/smtp` => `smtp`
  - `std/db_common` => `db_connector/db_common`
  - `std/db_sqlite` => `db_connector/db_sqlite`
  - `std/db_mysql` => `db_connector/db_mysql`
  - `std/db_postgres` => `db_connector/db_postgres`
  - `std/db_odbc` => `db_connector/db_odbc`

- Previously, calls like `foo(a, b): ...` or `foo(a, b) do: ...` where the final argument of
  `foo` had type `proc ()` were assumed by the compiler to mean `foo(a, b, proc () = ...)`.
  This behavior is now deprecated. Use `foo(a, b) do (): ...` or `foo(a, b, proc () = ...)` instead.

- If no exception or any exception deriving from Exception but not Defect or CatchableError given in except, a `warnBareExcept` warning will be triggered.

## Standard library additions and changes


- OpenSSL 3 is now supported.
- `macros.parseExpr` and `macros.parseStmt` now accept an optional
  filename argument for more informative errors.
- Module `colors` expanded with missing colors from the CSS color standard.
  `colPaleVioletRed` and `colMediumPurple` have also been changed to match the CSS color standard.
- Fixed `lists.SinglyLinkedList` being broken after removing the last node ([#19353](https://github.com/nim-lang/Nim/pull/19353)).
- The `md5` module now works at compile time and in JavaScript.
- Changed `mimedb` to use an `OrderedTable` instead of `OrderedTableRef` to support `const` tables.
- `strutils.find` now uses and defaults to `last = -1` for whole string searches,
  making limiting it to just the first char (`last = 0`) valid.
- `random.rand` now works with `Ordinal`s.
- Undeprecated `os.isvalidfilename`.
- `std/oids` now uses `int64` to store time internally (before it was int32).
- `std/uri.Uri` dollar `$` improved, precalculates the `string` result length from the `Uri`.
- `std/uri.Uri.isIpv6` is now exported.
- `std/logging.ConsoleLogger` and `FileLogger` now have a `flushThreshold` attribute to set what log message levels are automatically flushed. For Nim v1 use `-d:nimFlushAllLogs` to automatically flush all message levels. Flushing all logs is the default behavior for Nim v2.


- `std/net.IpAddress` dollar `$` improved, uses a fixed capacity for the `string` result based from the `IpAddressFamily`.
- `std/jsfetch.newFetchOptions` now has default values for all parameters
- `std/jsformdata` now accepts `Blob` data type.



- Added ISO 8601 week date utilities in `times`:
  - Added `IsoWeekRange`, a range type for weeks in a week-based year.
  - Added `IsoYear`, a distinct type for a week-based year in contrast to a regular year.
  - Added a `initDateTime` overload to create a datetime from an ISO week date.
  - Added `getIsoWeekAndYear` to get an ISO week number and week-based year from a datetime.
  - Added `getIsoWeeksInYear` to return the number of weeks in a week-based year.
- Added new modules which were part of `std/os`:
  - Added `std/oserrors` for OS error reporting. Added `std/envvars` for environment variables handling.
  - Added `std/paths`, `std/dirs`, `std/files`, `std/symlinks` and `std/appdirs`.
  - Added `std/cmdline` for reading command line parameters.
- Added `sep` parameter in `std/uri` to specify the query separator.
- Added bindings to [`Array.shift`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/shift)
  and [`queueMicrotask`](https://developer.mozilla.org/en-US/docs/Web/API/queueMicrotask)
  in `jscore` for JavaScript targets.
- Added `UppercaseLetters`, `LowercaseLetters`, `PunctuationChars`, `PrintableChars` sets to `std/strutils`.
- Added `complex.sgn` for obtaining the phase of complex numbers.
- Added `insertAdjacentText`, `insertAdjacentElement`, `insertAdjacentHTML`,
  `after`, `before`, `closest`, `append`, `hasAttributeNS`, `removeAttributeNS`,
  `hasPointerCapture`, `releasePointerCapture`, `requestPointerLock`,
  `replaceChildren`, `replaceWith`, `scrollIntoViewIfNeeded`, `setHTML`,
  `toggleAttribute`, and `matches` to `std/dom`.
- Added [`jsre.hasIndices`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/RegExp/hasIndices)
- Added `capacity` for `string` and `seq` to return the current capacity, see https://github.com/nim-lang/RFCs/issues/460
- Added `openArray[char]` overloads for `std/parseutils` allowing more code reuse.
- Added `openArray[char]` overloads for `std/unicode` allowing more code reuse.
- Added `safe` parameter to `base64.encodeMime`.


- Deprecated `selfExe` for Nimscript.
- Deprecated `std/sums`.
- Deprecated `std/base64.encode` for collections of arbitrary integer element type.
  Now only `byte` and `char` are supported.


- Removed deprecated module `parseopt2`.
- Removed deprecated module `sharedstrings`.
- Removed deprecated module `dom_extensions`.
- Removed deprecated module `LockFreeHash`.
- Removed deprecated module `events`.
- Removed deprecated `oids.oidToString`.
- Removed define `nimExperimentalAsyncjsThen` for `std/asyncjs.then` and `std/jsfetch`.
- Removed deprecated `jsre.test` and `jsre.toString`.
- Removed deprecated `math.c_frexp`.
- Removed deprecated `` httpcore.`==` ``.
- Removed deprecated `std/posix.CMSG_SPACE` and `std/posix.CMSG_LEN` that takes wrong argument types.
- Removed deprecated `osproc.poDemon`, symbol with typo.
- Removed deprecated `tables.rightSize`.


- Removed deprecated `posix.CLONE_STOPPED`.


## Language changes

- [Tag tracking](https://nim-lang.github.io/Nim/manual.html#effect-system-tag-tracking) supports the definition of forbidden tags by the `.forbids` pragma
  which can be used to disable certain effects in proc types.
- [Case statement macros](https://nim-lang.github.io/Nim/manual.html#macros-case-statement-macros) are no longer experimental,
  meaning you no longer need to enable the experimental switch `caseStmtMacros` to use them.
- Full command syntax and block arguments i.e. `foo a, b: c` are now allowed
  for the right-hand side of type definitions in type sections. Previously
  they would error with "invalid indentation".

- Compile-time define changes:
  - `defined` now accepts identifiers separated by dots, i.e. `defined(a.b.c)`.
    In the command line, this is defined as `-d:a.b.c`. Older versions can
    use accents as in ``defined(`a.b.c`)`` to access such defines.
  - [Define pragmas for constants](https://nim-lang.github.io/Nim/manual.html#implementation-specific-pragmas-compileminustime-define-pragmas)
    now support a string argument for qualified define names.

    ```nim
    # -d:package.FooBar=42
    const FooBar {.intdefine: "package.FooBar".}: int = 5
    echo FooBar # 42
    ```

    This was added to help disambiguate similar define names for different packages.
    In older versions, this could only be achieved with something like the following:

    ```nim
    const FooBar = block:
      const `package.FooBar` {.intdefine.}: int = 5
      `package.FooBar`
    ```
  - A generic `define` pragma for constants has been added that interprets
    the value of the define based on the type of the constant value.
    See the [experimental manual](https://nim-lang.github.io/Nim/manual_experimental.html#generic-define-pragma)
    for a list of supported types.

- [Macro pragmas](https://nim-lang.github.io/Nim/manual.html#userminusdefined-pragmas-macro-pragmas) changes:
  - Templates now accept macro pragmas.
  - Macro pragmas for var/let/const sections have been redesigned in a way that works
    similarly to routine macro pragmas. The new behavior is documented in the
    [experimental manual](https://nim-lang.github.io/Nim/manual_experimental.html#extended-macro-pragmas).
  - Pragma macros on type definitions can now return `nnkTypeSection` nodes as well as `nnkTypeDef`,
    allowing multiple type definitions to be injected in place of the original type definition.

    ```nim
    import macros
    macro multiply(amount: static int, s: untyped): untyped =
      let name = $s[0].basename
      result = newNimNode(nnkTypeSection)
      for i in 1 .. amount:
        result.add(newTree(nnkTypeDef, ident(name & $i), s[1], s[2]))
    type
      Foo = object
      Bar {.multiply: 3.} = object
        x, y, z: int
      Baz = object
    # becomes
    type
      Foo = object
      Bar1 = object
        x, y, z: int
      Bar2 = object
        x, y, z: int
      Bar3 = object
        x, y, z: int
      Baz = object
    ```

- A new form of type inference called [top-down inference](https://nim-lang.github.io/Nim/manual_experimental.html#topminusdown-type-inference)
  has been implemented for a variety of basic cases. For example, code like the following now compiles:

  ```nim
  let foo: seq[(float, byte, cstring)] = @[(1, 2, "abc")]

  • cstring is now accepted as a selector in case statements, removing the need to convert to string. On the JS backend, this is translated directly to a switch statement.

  • Nim now supports out parameters and "strict definitions".

  • Nim now offers a strict mode for case objects.

Compiler changes

  • The gc switch has been renamed to mm ("memory management") in order to reflect the reality better. (Nim moved away from all techniques based on "tracing".)

  • Defines the gcRefc symbol which allows writing specific code for the refc GC.

  • nim can now compile version 1.4.0 as follows: nim c --lib:lib --stylecheck:off compiler/nim, without requiring -d:nimVersion140 which is now a noop.

  • --styleCheck, --hintAsError and --warningAsError now only apply to the current package.

  • The switch --nimMainPrefix:prefix has been added to add a prefix to the names of NimMain and related functions produced on the backend. This prevents conflicts with other Nim static libraries.

  • When compiling for Release the flag -fno-math-errno is used for GCC.

Tool changes

  • Nim now ships Nimble version 0.14 which added support for lock-files. Libraries are stored in $nimbleDir/pkgs2 (it was $nimbleDir/pkgs).