utility handler fn extraction

internal/rest/api_work_item.go

@@ -1,16 +1,13 @@
 package rest
 
 import (
-	"bytes"
 	"encoding/json"
-	"io"
 	"net/http"
 
 	"github.com/danicc097/openapi-go-gin-postgres-sqlc/internal"
 	"github.com/danicc097/openapi-go-gin-postgres-sqlc/internal/repos"
 	"github.com/danicc097/openapi-go-gin-postgres-sqlc/internal/repos/postgresql/gen/models"
 	"github.com/danicc097/openapi-go-gin-postgres-sqlc/internal/services"
-	"github.com/danicc097/openapi-go-gin-postgres-sqlc/internal/tracing"
 	"github.com/gin-gonic/gin"
 )
 
@@ -29,28 +26,14 @@ func (h *StrictHandlers) DeleteWorkitem(c *gin.Context, request DeleteWorkitemRe
 func (h *StrictHandlers) CreateWorkitem(c *gin.Context, request CreateWorkitemRequestObject) (CreateWorkitemResponseObject, error) {
 	ctx := c.Request.Context()
 
-	span := GetSpanFromCtx(c)
-
 	caller, _ := GetUserCallerFromCtx(c)
 	tx := GetTxFromCtx(c)
 
-	jsonBody, err := io.ReadAll(c.Request.Body)
-	if err != nil {
-		renderErrorResponse(c, "Failed to read request body", err)
-	}
-	span.SetAttributes(tracing.MetadataAttribute(jsonBody))
-	c.Request.Body = io.NopCloser(bytes.NewBuffer(jsonBody))
-
-	project, err := projectByDiscriminator(request.Body)
-	if err != nil {
-		renderErrorResponse(c, "Failed to get project", err)
-	}
+	addRequestBodyToSpan(c)
 
 	var res any // depends on project
-	b, err := request.Body.ValueByDiscriminator()
-	if err != nil {
-		renderErrorResponse(c, "Failed to read discriminator", err)
-	}
+
+	project, b := projectAndBodyByDiscriminator(c, request.Body)
 
 	//exhaustive:enforce
 	switch project {

internal/rest/discriminator.go

@@ -1,20 +1,25 @@
 package rest
 
 import (
-	"fmt"
-
 	"github.com/danicc097/openapi-go-gin-postgres-sqlc/internal/repos/postgresql/gen/models"
+	"github.com/gin-gonic/gin"
 )
 
 type PolymorphicBody interface {
 	Discriminator() (string, error)
+	ValueByDiscriminator() (interface{}, error)
 }
 
-func projectByDiscriminator(b PolymorphicBody) (models.ProjectName, error) {
-	d, err := b.Discriminator()
+func projectAndBodyByDiscriminator(c *gin.Context, body PolymorphicBody) (models.ProjectName, interface{}) {
+	d, err := body.Discriminator()
+	if err != nil {
+		renderErrorResponse(c, "could not get project discriminator: %w", err)
+	}
+
+	b, err := body.ValueByDiscriminator()
 	if err != nil {
-		return "", fmt.Errorf("could not get project discriminator: %w", err)
+		renderErrorResponse(c, "Failed to read discriminator", err)
 	}
 
-	return models.ProjectName(d), nil
+	return models.ProjectName(d), b
 }

internal/rest/otel.go

@@ -1,6 +1,9 @@
 package rest
 
 import (
+	"bytes"
+	"io"
+
 	"github.com/danicc097/openapi-go-gin-postgres-sqlc/internal"
 	"github.com/danicc097/openapi-go-gin-postgres-sqlc/internal/tracing"
 	"github.com/gin-gonic/gin"
@@ -38,3 +41,14 @@ func newOTelSpanWithUser(c *gin.Context, opts ...trace.SpanStartOption) trace.Sp
 
 	return builder.Build(c.Request.Context())
 }
+
+func addRequestBodyToSpan(c *gin.Context) {
+	span := GetSpanFromCtx(c)
+
+	jsonBody, err := io.ReadAll(c.Request.Body)
+	if err != nil {
+		renderErrorResponse(c, "Failed to read request body", err)
+	}
+	span.SetAttributes(tracing.MetadataAttribute(jsonBody))
+	c.Request.Body = io.NopCloser(bytes.NewBuffer(jsonBody))
+}

internal/rest/responses.go

@@ -38,6 +38,9 @@ func WithoutPanic() RenderErrorOption {
 }
 
 // renderErrorResponse writes an error response from title and error.
+// When used inside a StrictHandlers' handler, it panics with a HandlerExitError which
+// is recovered immediately by the handler wrapper.
+// When used outside a StrictHandlers' handler, WithoutPanic must be used to prevent unrecovered panics.
 // title represents an error title which will be shown to end users.
 // Inspired by https://www.rfc-editor.org/rfc/rfc7807.
 func renderErrorResponse(c *gin.Context, title string, err error, opts ...RenderErrorOption) {