Add customizable context format and value conversion

[WarLikeLaux]

Q	A
Is bugfix?	❌
New feature?	✔️
Docs added?	✔️
Tests added?	✔️
Breaks BC?	❌
Fixed issues	#99

What does this PR do?

Add three new methods to Formatter and Target for customizing context output:

• setConvertToString(callable) - custom value-to-string conversion
• setContextTemplate(string) - string template for reordering context sections
• setContextFormat(callable) - full control over context rendering via callable

Use cases

setConvertToString allows replacing the default VarDumper-based conversion. For example, to JSON-encode all context values:

$target->setConvertToString(static fn(mixed $value): string => json_encode($value));

setContextTemplate reorders sections via {trace}, {message}, {common} placeholders. Empty sections are omitted automatically:

$target->setContextTemplate("{common}{message}{trace}\n");

setContextFormat gives full control over context rendering, including custom headers:

$target->setContextFormat(
    static function (string $trace, string $messageContext, string $commonContext): string {
        $result = '';
        if ($commonContext !== '') {
            $result .= "\n\nCommon:\n" . $commonContext;
        }
        if ($messageContext !== '') {
            $result .= "\n\nMessage:\n" . $messageContext;
        }
        if ($trace !== '') {
            $result .= "\n\nTrace:\n" . $trace;
        }
        return $result;
    },
);

Priority: setContextFormat > setContextTemplate > default behavior.

No BC break: new methods, default output unchanged.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (1d415af) to head (82d7b3b).
⚠️ Report is 2 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff             @@
##              master      #140   +/-   ##
===========================================
  Coverage     100.00%   100.00%           
- Complexity       163       178   +15     
===========================================
  Files             11        11           
  Lines            449       494   +45     
===========================================
+ Hits             449       494   +45     

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[Copilot]

Pull request overview

Adds new configuration hooks to customize how log context is rendered and how context values are converted to strings, enabling user-defined context ordering and formatting while keeping the default output unchanged.

Changes:

• Add setConvertToString(), setContextTemplate(), and setContextFormat() APIs on Target/Formatter and implement precedence rules in formatting.
• Update formatter context assembly to support template-based section ordering and fully custom rendering via callable.
• Add/extend tests and documentation covering the new customization options.

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
src/Message/Formatter.php	Implements custom context formatting/template logic and pluggable value-to-string conversion.
src/Target.php	Exposes new formatter customization methods at the target level.
tests/Message/FormatterTest.php	Adds coverage for new formatter customization behaviors and precedence/error cases.
tests/TargetTest.php	Adds target-level tests for new customization methods.
tests/TestAsset/DummyTarget.php	Ensures test target mirrors new formatter customization settings for exported formatting.
README.md	Documents new formatting customization options and examples.
CHANGELOG.md	Records the new feature in the upcoming release notes.

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[vjik]

@WarLikeLaux resolve conflicts, please

[vjik]

What about use constructor parameters instead of methods?

[vjik]

What about use constructor parameters instead of methods?

In another PR, mark existing methods as deprecated and also move to constructor?

@samdark WDYT?

[vjik]

Suggested change

	private $convertToString;
	private $stringConverter;

[vjik]

Move default converter to separate class and use it as default value for convertToString.

[vjik]

What about merge $contextTemplate and $contextFormatter to one property string|callable|null $contextFormat?