initial commit

.github/workflows/ci.yaml

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+name: CI
+
+on:
+  push:
+    branches:
+    - main
+  pull_request:
+  workflow_dispatch:
+
+permissions:
+  contents: read
+  pull-requests: read
+
+jobs:
+  ci:
+    name: ci | ${{ matrix.go_version }}
+    runs-on: ubuntu-latest
+
+    strategy:
+      matrix:
+        go_version: ["1.21"]
+
+    steps:
+    - uses: actions/setup-go@v4
+      with:
+        go-version: ${{ matrix.go_version }}
+    - uses: actions/checkout@v3
+    - name: golangci-lint
+      uses: golangci/golangci-lint-action@v3
+      with:
+        only-new-issues: true
+
+    - name: Make out dir
+      run: |
+        mkdir out
+
+    - name: Run tests
+      run: |
+        go test -race ./... -coverprofile=out/coverage.txt -covermode=atomic
+
+    - name: Upload coverage
+      uses: codecov/codecov-action@v2
+      with:
+        files: out/coverage.txt
+
+  # Ensures all matrix jobs complete before passing the build
+  complete:
+    name: complete
+    if: ${{ always() }}
+    needs: [ci]
+    runs-on: ubuntu-latest
+    steps:
+    - name: Check that all steps completed
+      run: |
+        [ "${{ needs.ci.result }}" != "success" ] && echo "CI failed." && exit 1;
+
+        echo "CI succeeded!";
+        exit 0;

README.md

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+# slogctx
+
+Simple [slog](https://pkg.go.dev/log/slog) wrapping handler that lets you pass fields down to a slog call through context.
+
+

go.mod

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+module github.com/aidenwallis/slogctx
+
+go 1.21

handler.go

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+package slogctx
+
+import (
+	"context"
+	"log/slog"
+)
+
+type contextKey uint8
+
+const (
+	argsKey contextKey = iota
+)
+
+// GetArgs returns the args currently found in context, or nil
+func GetArgs(ctx context.Context) []any {
+	if v, ok := ctx.Value(argsKey).([]any); ok {
+		return v
+	}
+	return nil
+}
+
+// WithArgs appends slog args to context
+func WithArgs(ctx context.Context, args ...any) context.Context {
+	return context.WithValue(ctx, argsKey, append(GetArgs(ctx), args...))
+}
+
+// Handler wraps a given slog handler, and applies extra fields to the call
+type Handler struct {
+	slog.Handler
+}
+
+var _ slog.Handler = (*Handler)(nil)
+
+// NewHandler creates a new instance of Handler
+func NewHandler(handler slog.Handler) *Handler {
+	return &Handler{Handler: handler}
+}
+
+// Handle appends any fields from context to the record and calls the nested handler
+func (h *Handler) Handle(ctx context.Context, r slog.Record) error {
+	if v := GetArgs(ctx); len(v) > 0 {
+		r.Add(v...)
+	}
+
+	return h.Handler.Handle(ctx, r)
+}

handler_test.go

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+package slogctx_test
+
+import (
+	"context"
+	"log/slog"
+	"testing"
+
+	"github.com/aidenwallis/slogctx"
+)
+
+type testHandler struct {
+	slog.Handler
+	lastRecord slog.Record
+	ch         chan struct{}
+}
+
+func (h *testHandler) wait() {
+	<-h.ch
+}
+
+func (h *testHandler) Handle(ctx context.Context, r slog.Record) error {
+	h.lastRecord = r
+	h.ch <- struct{}{}
+	return nil
+}
+
+var _ slog.Handler = (*testHandler)(nil)
+
+func TestHandler(t *testing.T) {
+	ctx := context.Background()
+
+	handler := &testHandler{
+		Handler: slog.NewTextHandler(nil, nil),
+		ch:      make(chan struct{}, 1), // allows the test to pause for the lastRecord to be written
+	}
+	logger := slog.New(slogctx.NewHandler(handler))
+
+	// default case: should have 0 attrs
+	logger.InfoContext(ctx, "test message")
+	handler.wait()
+	assert(t, handler.lastRecord.NumAttrs(), 0)
+
+	ctx = slogctx.WithArgs(ctx, "abc", 123)
+
+	// should now have 1 attr from the ctx
+	logger.InfoContext(ctx, "test message")
+	handler.wait()
+	assert(t, handler.lastRecord.NumAttrs(), 1)
+}
+
+func assert[T comparable](t *testing.T, in, expected T) {
+	t.Helper()
+
+	if in != expected {
+		t.Fatalf("expected %#v but got %#v", expected, in)
+	}
+}

view-coverage.sh

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+#!/bin/sh
+
+# This small script simply runs the tests and opens a browser window of the results.
+# From: https://stackoverflow.com/a/27284510
+
+t="/tmp/go-cover.$$.tmp"
+go test -coverprofile=$t -race ./... $@ && go tool cover -html=$t && unlink $t