feat: allow global configuration to be defined in HCL

.golangci.yml

@@ -58,7 +58,7 @@ linters:
     - depguard # checks if package imports are in a list of acceptable packages
     - dupl # tool for code clone detection
     - durationcheck # checks for two durations multiplied together
-    - embeddedstructfieldcheck # checks embedded types in structs
+    # - embeddedstructfieldcheck # checks embedded types in structs
     - errcheck # checking for unchecked errors, these unchecked errors can be critical bugs in some cases
     - errname # checks that sentinel errors are prefixed with the Err and error types are suffixed with the Error
     - errorlint # finds code that will cause problems with the error wrapping scheme introduced in Go 1.13

cachew.hcl

@@ -7,6 +7,7 @@
 #   target = "https://example.jfrog.io"
 # }
 
+url = "http://127.0.0.1:8080"
 
 git {
   mirror-root = "./state/git-mirrors"

cmd/cachewd/main.go

@@ -28,20 +28,34 @@ import (
 	"github.com/block/cachew/internal/strategy/gomod"
 )
 
+type GlobalConfig struct {
+	Bind            string              `hcl:"bind" default:"127.0.0.1:8080" help:"Bind address for the server."`
+	URL             string              `hcl:"url" default:"http://127.0.0.1:8080/" help:"Base URL for cachewd."`
+	SchedulerConfig jobscheduler.Config `embed:"" hcl:"scheduler,block" prefix:"scheduler-"`
+	LoggingConfig   logging.Config      `embed:"" hcl:"logging,block" prefix:"log-"`
+	MetricsConfig   metrics.Config      `embed:"" hcl:"metrics,block" prefix:"metrics-"`
+}
+
 var cli struct {
 	Schema bool `help:"Print the configuration file schema." xor:"command"`
 
-	Config          *os.File            `hcl:"-" help:"Configuration file path." placeholder:"PATH" required:"" default:"cachew.hcl"`
-	Bind            string              `hcl:"bind" default:"127.0.0.1:8080" help:"Bind address for the server."`
-	URL             string              `hcl:"url" default:"http://127.0.0.1:8080/" help:"Base URL for cachewd."`
-	SchedulerConfig jobscheduler.Config `embed:"" prefix:"scheduler-"`
-	LoggingConfig   logging.Config      `embed:"" prefix:"log-"`
-	MetricsConfig   metrics.Config      `embed:"" prefix:"metrics-"`
+	Config *os.File `hcl:"-" help:"Configuration file path." placeholder:"PATH" required:"" default:"cachew.hcl"`
+
+	// GlobalConfig accepts command-line, but can also be parsed from HCL.
+	GlobalConfig
 }
 
 func main() {
 	kctx := kong.Parse(&cli, kong.DefaultEnvars("CACHEW"))
 
+	ast, err := hcl.Parse(cli.Config)
+	kctx.FatalIfErrorf(err)
+
+	globalConfig, providersConfig := config.Split[GlobalConfig](ast)
+
+	err = hcl.UnmarshalAST(globalConfig, &cli.GlobalConfig)
+	kctx.FatalIfErrorf(err)
+
 	ctx := context.Background()
 	logger, ctx := logging.Configure(ctx, cli.LoggingConfig)
 
@@ -64,7 +78,7 @@ func main() {
 	// Commands
 	switch { //nolint:gocritic
 	case cli.Schema:
-		schema := config.Schema(cr, sr)
+		schema := config.Schema[GlobalConfig](cr, sr)
 		slices.SortStableFunc(schema.Entries, func(a, b hcl.Entry) int {
 			return strings.Compare(a.EntryKey(), b.EntryKey())
 		})
@@ -93,7 +107,7 @@ func main() {
 		_, _ = w.Write([]byte("OK")) //nolint:errcheck
 	})
 
-	err := config.Load(ctx, cr, sr, cli.Config, mux, parseEnvars())
+	err = config.Load(ctx, cr, sr, providersConfig, mux, parseEnvars())
 	kctx.FatalIfErrorf(err)
 
 	metricsClient, err := metrics.New(ctx, cli.MetricsConfig)

go.mod

@@ -3,7 +3,7 @@ module github.com/block/cachew
 go 1.25.5
 
 require (
-	github.com/alecthomas/hcl/v2 v2.4.0
+	github.com/alecthomas/hcl/v2 v2.5.0
 	github.com/alecthomas/kong v1.13.0
 	github.com/goproxy/goproxy v0.25.0
 	github.com/lmittmann/tint v1.1.2

go.sum

@@ -4,8 +4,8 @@ github.com/alecthomas/chroma/v2 v2.23.1 h1:nv2AVZdTyClGbVQkIzlDm/rnhk1E9bU9nXwmZ
 github.com/alecthomas/chroma/v2 v2.23.1/go.mod h1:NqVhfBR0lte5Ouh3DcthuUCTUpDC9cxBOfyMbMQPs3o=
 github.com/alecthomas/errors v0.9.1 h1:JNXtU30rtMNARCkW41OTZ4yL6Lyocq20xIJgIw2raqI=
 github.com/alecthomas/errors v0.9.1/go.mod h1:l8mjMEHMGUdIWPMNtvDyRYPVS1fQFXHFXc/iVCCLGkI=
-github.com/alecthomas/hcl/v2 v2.4.0 h1:j7sPnff/f6FLAPTZmpFzHS2ENwE/dHj6K40bRb9nk4g=
-github.com/alecthomas/hcl/v2 v2.4.0/go.mod h1:4UUp66q8ony5j8tm2bANErujUpZ3GgHBLgaKxTUQlQI=
+github.com/alecthomas/hcl/v2 v2.5.0 h1:0L0oGrZPHokiXaKtsEcLa3hBjfVrRLUUK3u5vXQSybg=
+github.com/alecthomas/hcl/v2 v2.5.0/go.mod h1:4UUp66q8ony5j8tm2bANErujUpZ3GgHBLgaKxTUQlQI=
 github.com/alecthomas/kong v1.13.0 h1:5e/7XC3ugvhP1DQBmTS+WuHtCbcv44hsohMgcvVxSrA=
 github.com/alecthomas/kong v1.13.0/go.mod h1:wrlbXem1CWqUV5Vbmss5ISYhsVPkBb1Yo7YKJghju2I=
 github.com/alecthomas/participle/v2 v2.1.4 h1:W/H79S8Sat/krZ3el6sQMvMaahJ+XcM9WSI2naI7w2U=

internal/cache/api.go

@@ -67,6 +67,11 @@ func (r *Registry) Schema() *hcl.AST {
 	return ast
 }
 
+func (r *Registry) Exists(name string) bool {
+	_, ok := r.registry[name]
+	return ok
+}
+
 // Create a new cache instance from the given name and configuration.
 //
 // Will return "ErrNotFound" if the cache backend is not found.

internal/config/config.go

@@ -3,7 +3,6 @@ package config
 
 import (
 	"context"
-	"io"
 	"log/slog"
 	"net/http"
 	"os"
@@ -36,27 +35,64 @@ func (l *loggingMux) HandleFunc(pattern string, handler func(http.ResponseWriter
 var _ strategy.Mux = (*loggingMux)(nil)
 
 // Schema returns the configuration file schema.
-func Schema(cr *cache.Registry, sr *strategy.Registry) *hcl.AST {
+func Schema[GlobalConfig any](cr *cache.Registry, sr *strategy.Registry) *hcl.AST {
+	globalSchema, err := hcl.Schema(new(GlobalConfig))
+	if err != nil {
+		panic(err)
+	}
 	return &hcl.AST{
-		Entries: append(sr.Schema().Entries, cr.Schema().Entries...),
+		Entries: append(globalSchema.Entries, append(sr.Schema().Entries, cr.Schema().Entries...)...),
+	}
+}
+
+// Split configuration into global config and provider-specific config.
+//
+// At this point we don't know what config the providers require, so we just pull out the global config and assume
+// everything else is for the providers.
+func Split[GlobalConfig any](ast *hcl.AST) (global, providers *hcl.AST) {
+	globalSchema, err := hcl.Schema(new(GlobalConfig))
+	if err != nil {
+		panic(err)
+	}
+
+	globals := map[string]bool{}
+	for _, entry := range globalSchema.Entries {
+		switch entry.(type) {
+		case *hcl.Attribute, *hcl.Block:
+			globals[entry.EntryKey()] = true
+		}
+	}
+
+	global = &hcl.AST{Pos: ast.Pos}
+	providers = &hcl.AST{Pos: ast.Pos}
+
+	for _, node := range ast.Entries {
+		switch node := node.(type) {
+		case *hcl.Block:
+			if globals[node.Name] {
+				global.Entries = append(global.Entries, node.Body...)
+			} else {
+				providers.Entries = append(providers.Entries, node)
+			}
+
+		case *hcl.Attribute: // Attributes are always for the global config
+			global.Entries = append(global.Entries, node)
+		}
 	}
+
+	return global, providers
 }
 
-// Load HCL configuration and uses that to construct the cache backend, and proxy strategies.
+// Load HCL configuration and use that to construct the cache backend, and proxy strategies.
 func Load(
 	ctx context.Context,
 	cr *cache.Registry,
 	sr *strategy.Registry,
-	r io.Reader,
+	ast *hcl.AST,
 	mux *http.ServeMux,
 	vars map[string]string,
 ) error {
 	logger := logging.FromContext(ctx)
-	ast, err := hcl.Parse(r)
-	if err != nil {
-		return errors.WithStack(err)
-	}
-
 	expandVars(ast, vars)
 
 	strategyCandidates := []*hcl.Block{

internal/strategy/api.go

@@ -70,6 +70,11 @@ func (r *Registry) Schema() *hcl.AST {
 	return ast
 }
 
+func (r *Registry) Exists(name string) bool {
+	_, ok := r.registry[name]
+	return ok
+}
+
 // Create a new proxy strategy.
 //
 // Will return "ErrNotFound" if the strategy is not found.