[GitHub] [trafficcontrol] rob05c commented on a diff in pull request #6756: Fix t3c TO API fallback

[GitBox <gi...@apache.org>]

rob05c commented on code in PR #6756:
URL: https://github.com/apache/trafficcontrol/pull/6756#discussion_r850777407


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cache-config/t3cutil/toreq/client.go:
##########
@@ -48,8 +48,22 @@ import (
 )
 
 type TOClient struct {
-	c          *toclient.Session
-	old        *toreqold.TOClient
+	// c is the "new" Traffic Ops client, for the latest major API.
+	//
+	// This MUST NOT be accessed without checking for nil.
+	// If the Traffic Ops server doesn't support the latest API, it will fall back,
+	// and c will be nil and old will not, and old must be used.
+	//
+	// **WARNING** This MUST NOT be accessed without checking for nil. See above.
+	c *toclient.Session

Review Comment:
   This is something of a footgun. This being the second panic we've had recently. It'd be really nice to make it impossible to happen, but that'd require quite a bit of abstraction, it'd be a lot of code. So for now, I added some giant warning comments on the symbol. If it happens again, we can reconsider if the abstraction to make it impossible is worth it.



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