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log/slog: rearrange package doc

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Move the "Attrs and Values" section lower. It describes an optimization;
the API it covers is not essential.

Also, move the brief section on Logger.With up to the first section.
It was in the "Groups" section but didn't belong there.

Change-Id: I0e36ef654e95f918d5b480566ec58d9990d26b40
Reviewed-on: https://go-review.googlesource.com/c/go/+/487856
Reviewed-by: Alan Donovan <adonovan@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Jonathan Amsterdam <jba@google.com>
This commit is contained in:
Jonathan Amsterdam 2023-04-23 11:06:34 -04:00
parent 2f5f231ac1
commit ae59562c71
1 changed files with 33 additions and 33 deletions
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66
src/log/slog/doc.go
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@ -78,38 +78,6 @@ will cause the top-level functions like [Info] to use it.
so that existing applications that use [log.Printf] and related functions
will send log records to the logger's handler without needing to be rewritten.
# Attrs and Values
An [Attr] is a key-value pair. The Logger output methods accept Attrs as well as
alternating keys and values. The statement
slog.Info("hello", slog.Int("count", 3))
behaves the same as
slog.Info("hello", "count", 3)
There are convenience constructors for [Attr] such as [Int], [String], and [Bool]
for common types, as well as the function [Any] for constructing Attrs of any
type.
The value part of an Attr is a type called [Value].
Like an [any], a Value can hold any Go value,
but it can represent typical values, including all numbers and strings,
without an allocation.
For the most efficient log output, use [Logger.LogAttrs].
It is similar to [Logger.Log] but accepts only Attrs, not alternating
keys and values; this allows it, too, to avoid allocation.
The call
logger.LogAttrs(nil, slog.LevelInfo, "hello", slog.Int("count", 3))
is the most efficient way to achieve the same output as
slog.Info("hello", "count", 3)
Some attributes are common to many log calls.
For example, you may wish to include the URL or trace identifier of a server request
with all log events arising from the request.
@ -164,7 +132,7 @@ How this qualification is displayed depends on the handler.
[TextHandler] separates the group and attribute names with a dot.
[JSONHandler] treats each group as a separate JSON object, with the group name as the key.
Use [Group] to create a Group Attr from a name and a list of key-value pairs:
Use [Group] to create a Group attribute from a name and a list of key-value pairs:
slog.Group("request",
"method", r.Method,
@ -212,6 +180,38 @@ in "Ctx" do. For example,
It is recommended to pass a context to an output method if one is available.
# Attrs and Values
An [Attr] is a key-value pair. The Logger output methods accept Attrs as well as
alternating keys and values. The statement
slog.Info("hello", slog.Int("count", 3))
behaves the same as
slog.Info("hello", "count", 3)
There are convenience constructors for [Attr] such as [Int], [String], and [Bool]
for common types, as well as the function [Any] for constructing Attrs of any
type.
The value part of an Attr is a type called [Value].
Like an [any], a Value can hold any Go value,
but it can represent typical values, including all numbers and strings,
without an allocation.
For the most efficient log output, use [Logger.LogAttrs].
It is similar to [Logger.Log] but accepts only Attrs, not alternating
keys and values; this allows it, too, to avoid allocation.
The call
logger.LogAttrs(nil, slog.LevelInfo, "hello", slog.Int("count", 3))
is the most efficient way to achieve the same output as
slog.Info("hello", "count", 3)
# Customizing a type's logging behavior
If a type implements the [LogValuer] interface, the [Value] returned from its LogValue