From d55b105dae295818e0cd705b48c7aaac36dd8333 Mon Sep 17 00:00:00 2001
From: Andrea Gottardo <andrea@tailscale.com>
Date: Tue, 18 Jun 2024 13:34:55 -0700
Subject: [PATCH] health: expose DependsOn to local API via UnhealthyState
 (#12513)

Updates #4136

Small PR to expose the health Warnables dependencies to the GUI via LocalAPI, so that we can only show warnings for root cause issues, and filter out unnecessary messages before user presentation.

Signed-off-by: Andrea Gottardo <andrea@gottardo.me>
---
 health/health_test.go | 35 +++++++++++++++++++++++++++++++++++
 health/state.go       | 11 +++++++++--
 2 files changed, 44 insertions(+), 2 deletions(-)

diff --git a/health/health_test.go b/health/health_test.go
index ff4cddb70..7bfe87242 100644
--- a/health/health_test.go
+++ b/health/health_test.go
@@ -176,3 +176,38 @@ func TestRegisterWarnablePanicsWithDuplicate(t *testing.T) {
 	}()
 	Register(w)
 }
+
+// TestCheckDependsOnAppearsInUnhealthyState asserts that the DependsOn field in the UnhealthyState
+// is populated with the WarnableCode(s) of the Warnable(s) that a warning depends on.
+func TestCheckDependsOnAppearsInUnhealthyState(t *testing.T) {
+	ht := Tracker{}
+	w1 := Register(&Warnable{
+		Code:      "w1",
+		Text:      StaticMessage("W1 Text"),
+		DependsOn: []*Warnable{},
+	})
+	defer unregister(w1)
+	w2 := Register(&Warnable{
+		Code:      "w2",
+		Text:      StaticMessage("W2 Text"),
+		DependsOn: []*Warnable{w1},
+	})
+	defer unregister(w2)
+
+	ht.SetUnhealthy(w1, Args{ArgError: "w1 is unhealthy"})
+	us1, ok := ht.CurrentState().Warnings[w1.Code]
+	if !ok {
+		t.Fatalf("Expected an UnhealthyState for w1, got nothing")
+	}
+	if len(us1.DependsOn) != 0 {
+		t.Fatalf("Expected no DependsOn in the unhealthy state, got: %v", us1.DependsOn)
+	}
+	ht.SetUnhealthy(w2, Args{ArgError: "w2 is also unhealthy now"})
+	us2, ok := ht.CurrentState().Warnings[w2.Code]
+	if !ok {
+		t.Fatalf("Expected an UnhealthyState for w2, got nothing")
+	}
+	if !reflect.DeepEqual(us2.DependsOn, []WarnableCode{w1.Code}) {
+		t.Fatalf("Expected DependsOn = [w1.Code] in the unhealthy state, got: %v", us2.DependsOn)
+	}
+}
diff --git a/health/state.go b/health/state.go
index 1b12898eb..bd7338381 100644
--- a/health/state.go
+++ b/health/state.go
@@ -27,8 +27,9 @@ type UnhealthyState struct {
 	Severity     Severity
 	Title        string
 	Text         string
-	BrokenSince  *time.Time `json:",omitempty"`
-	Args         Args       `json:",omitempty"`
+	BrokenSince  *time.Time     `json:",omitempty"`
+	Args         Args           `json:",omitempty"`
+	DependsOn    []WarnableCode `json:",omitempty"`
 }
 
 // unhealthyState returns a unhealthyState of the Warnable given its current warningState.
@@ -40,6 +41,11 @@ func (w *Warnable) unhealthyState(ws *warningState) *UnhealthyState {
 		text = w.Text(Args{})
 	}
 
+	dependsOnWarnableCodes := make([]WarnableCode, len(w.DependsOn))
+	for i, d := range w.DependsOn {
+		dependsOnWarnableCodes[i] = d.Code
+	}
+
 	return &UnhealthyState{
 		WarnableCode: w.Code,
 		Severity:     w.Severity,
@@ -47,6 +53,7 @@ func (w *Warnable) unhealthyState(ws *warningState) *UnhealthyState {
 		Text:         text,
 		BrokenSince:  &ws.BrokenSince,
 		Args:         ws.Args,
+		DependsOn:    dependsOnWarnableCodes,
 	}
 }