Add static analyzer to discourage use of panic() (#15075)

* Implement static analysis to prevent panics

* Add nopanic to nogo

* Fix violations and add exclusions

Fix violations and add exclusions for all

* Changelog fragment

* Use pass.Report instead of pass.Reportf

* Remove strings.ToLower for checking init method name

* Add exclusion for herumi init

* Move api/client/beacon template function to init and its own file

* Fix nopanic testcase

api/client/beacon/BUILD.bazel

@@ -7,6 +7,7 @@ go_library(
         "doc.go",
         "health.go",
         "log.go",
+        "template.go",
     ],
     importpath = "github.com/prysmaticlabs/prysm/v5/api/client/beacon",
     visibility = ["//visibility:public"],

api/client/beacon/client.go

@@ -11,7 +11,6 @@ import (
 	"regexp"
 	"sort"
 	"strconv"
-	"text/template"
 
 	"github.com/ethereum/go-ethereum/common/hexutil"
 	"github.com/pkg/errors"
@@ -64,23 +63,6 @@ func IdFromSlot(s primitives.Slot) StateOrBlockId {
 	return StateOrBlockId(strconv.FormatUint(uint64(s), 10))
 }
 
-// idTemplate is used to create template functions that can interpolate StateOrBlockId values.
-func idTemplate(ts string) func(StateOrBlockId) string {
-	t := template.Must(template.New("").Parse(ts))
-	f := func(id StateOrBlockId) string {
-		b := bytes.NewBuffer(nil)
-		err := t.Execute(b, struct{ Id string }{Id: string(id)})
-		if err != nil {
-			panic(fmt.Sprintf("invalid idTemplate: %s", ts))
-		}
-		return b.String()
-	}
-	// run the template to ensure that it is valid
-	// this should happen load time (using package scoped vars) to ensure runtime errors aren't possible
-	_ = f(IdGenesis)
-	return f
-}
-
 // RenderGetBlockPath formats a block id into a path for the GetBlock API endpoint.
 func RenderGetBlockPath(id StateOrBlockId) string {
 	return path.Join(getSignedBlockPath, string(id))
@@ -114,8 +96,6 @@ func (c *Client) GetBlock(ctx context.Context, blockId StateOrBlockId) ([]byte,
 	return b, nil
 }
 
-var getBlockRootTpl = idTemplate(getBlockRootPath)
-
 // GetBlockRoot retrieves the hash_tree_root of the BeaconBlock for the given block id.
 // Block identifier can be one of: "head" (canonical head in node's view), "genesis", "finalized",
 // <slot>, <hex encoded blockRoot with 0x prefix>. Variables of type StateOrBlockId are exported by this package
@@ -138,8 +118,6 @@ func (c *Client) GetBlockRoot(ctx context.Context, blockId StateOrBlockId) ([32]
 	return bytesutil.ToBytes32(rs), nil
 }
 
-var getForkTpl = idTemplate(getForkForStatePath)
-
 // GetFork queries the Beacon Node API for the Fork from the state identified by stateId.
 // Block identifier can be one of: "head" (canonical head in node's view), "genesis", "finalized",
 // <slot>, <hex encoded blockRoot with 0x prefix>. Variables of type StateOrBlockId are exported by this package

api/client/beacon/template.go

@@ -0,0 +1,34 @@
+package beacon
+
+import (
+	"bytes"
+	"fmt"
+	"text/template"
+)
+
+type templateFn func(StateOrBlockId) string
+
+var getBlockRootTpl templateFn
+var getForkTpl templateFn
+
+func init() {
+	// idTemplate is used to create template functions that can interpolate StateOrBlockId values.
+	idTemplate := func(ts string) func(StateOrBlockId) string {
+		t := template.Must(template.New("").Parse(ts))
+		f := func(id StateOrBlockId) string {
+			b := bytes.NewBuffer(nil)
+			err := t.Execute(b, struct{ Id string }{Id: string(id)})
+			if err != nil {
+				panic(fmt.Sprintf("invalid idTemplate: %s", ts))
+			}
+			return b.String()
+		}
+		// run the template to ensure that it is valid
+		// this should happen load time (using package scoped vars) to ensure runtime errors aren't possible
+		_ = f(IdGenesis)
+		return f
+	}
+
+	getBlockRootTpl = idTemplate(getBlockRootPath)
+	getForkTpl = idTemplate(getForkForStatePath)
+}