Updates Semgrep rule setfield-without-assign to support assigning a new context

Author: gdavison

.ci/semgrep/tflog/tflog.go

@@ -0,0 +1,46 @@
+package main
+
+import (
+	"context"
+
+	"github.com/hashicorp/terraform-plugin-log/tflog"
+)
+
+func noAssignment() {
+	ctx := context.Background()
+
+	// ruleid: setfield-without-assign
+	tflog.SetField(ctx, "field", "value")
+}
+
+func assigned() {
+	ctx := context.Background()
+
+	// ok: setfield-without-assign
+	ctx = tflog.SetField(ctx, "field", "value")
+}
+
+func returnedContext() context.Context {
+	ctx := context.Background()
+
+	// ok: setfield-without-assign
+	return tflog.SetField(ctx, "field", "value")
+}
+
+func declareAndAssign_SameName() {
+	ctx := context.Background()
+
+	for i := 0; i < 1; i++ {
+		// ok: setfield-without-assign
+		ctx := tflog.SetField(ctx, "field", "value")
+	}
+}
+
+func declareAndAssign_Rename() {
+	outerCtx := context.Background()
+
+	for i := 0; i < 1; i++ {
+		// ok: setfield-without-assign
+		innerCtx := tflog.SetField(outerCtx, "field", "value")
+	}
+}

.ci/semgrep/tflog/tflog.yml

@@ -4,6 +4,6 @@ rules:
     message: The return value of "tflog.SetField" must be used
     patterns:
       - pattern: tflog.SetField(...)
-      - pattern-not-inside: $CTX = tflog.SetField($CTX, ...)
+      - pattern-not-inside: $CTX1 = tflog.SetField($CTX2, ...)
       - pattern-not-inside: return tflog.SetField($CTX, ...)
     severity: ERROR