node-expr fails on valid labels

[jabbrwcky]

the nexpression parser used for node-expr fails - or even worse panics - on several classes of valid node labels, e.g.

draino-enabled=true, kubernetes.io/os=linux ordraino="true". (Examples below)

So either a different expression parser would be nice or at least adding a caveat to the documentation.

Some snippts to try in nodefilter_test.go:

{
	name: "ParseBoolean",
	obj: &core.Node{
		ObjectMeta: meta.ObjectMeta{
			Name:   nodeName,
			Labels: map[string]string{"metadata.labels.draino-enabled": "true"},
		},
	},
	expression:   "metadata.labels.draino-enabled == 'true'",
	passesFilter: true,
},

blows up completely

Running tool: /opt/homebrew/bin/go test -timeout 30s -run ^TestNodeLabelFilter$ github.com/planetlabs/draino/internal/kubernetes

2021-10-04T18:08:40.204+0200	ERROR	kubernetes/nodefilters.go:62	Could not parse expression: invalid operation: string - <nil> (1:23)
 | metadata.labels.draino-enabled == 'true'
 | ......................^
github.com/planetlabs/draino/internal/kubernetes.NewNodeLabelFilter.func1
	/Users/jenshausherr/src/draino/internal/kubernetes/nodefilters.go:62
github.com/planetlabs/draino/internal/kubernetes.TestNodeLabelFilter.func1
	/Users/jenshausherr/src/draino/internal/kubernetes/nodefilters_test.go:235
testing.tRunner
	/opt/homebrew/Cellar/go/1.17.1/libexec/src/testing/testing.go:1259
--- FAIL: TestNodeLabelFilter (0.00s)
    --- FAIL: TestNodeLabelFilter/Panics (0.00s)
panic: interface conversion: interface {} is nil, not bool [recovered]
	panic: interface conversion: interface {} is nil, not bool

goroutine 6 [running]:
testing.tRunner.func1.2({0x101122d60, 0x1400041f4d0})
	/opt/homebrew/Cellar/go/1.17.1/libexec/src/testing/testing.go:1209 +0x258
testing.tRunner.func1(0x1400044a1a0)
	/opt/homebrew/Cellar/go/1.17.1/libexec/src/testing/testing.go:1212 +0x284
panic({0x101122d60, 0x1400041f4d0})
	/opt/homebrew/Cellar/go/1.17.1/libexec/src/runtime/panic.go:1038 +0x21c
github.com/planetlabs/draino/internal/kubernetes.NewNodeLabelFilter.func1({0x1012192e0, 0x140002e3340})
	/Users/jenshausherr/src/draino/internal/kubernetes/nodefilters.go:64 +0x238
github.com/planetlabs/draino/internal/kubernetes.TestNodeLabelFilter.func1(0x1400044a1a0)
	/Users/jenshausherr/src/draino/internal/kubernetes/nodefilters_test.go:235 +0xc8
testing.tRunner(0x1400044a1a0, 0x1400000e918)
	/opt/homebrew/Cellar/go/1.17.1/libexec/src/testing/testing.go:1259 +0x104
created by testing.(*T).Run
	/opt/homebrew/Cellar/go/1.17.1/libexec/src/testing/testing.go:1306 +0x328
FAIL	github.com/planetlabs/draino/internal/kubernetes	0.119s
FAIL

as well as

{
	name: "AlsoPanics",
	obj: &core.Node{
		ObjectMeta: meta.ObjectMeta{
			Name:   nodeName,
			Labels: map[string]string{"metadata.labels.kubernetes.io/os": "linux"},
		},
	},
	expression:   "metadata.labels.kubernetes.io/os == 'linux'",
	passesFilter: true,
},

Running tool: /opt/homebrew/bin/go test -timeout 30s -run ^TestNodeLabelFilter$ github.com/planetlabs/draino/internal/kubernetes

2021-10-04T18:10:38.596+0200	ERROR	kubernetes/nodefilters.go:62	Could not parse expression: invalid operation: int(string) (1:28)
 | metadata.labels.kubernetes.io/os == 'linux'
 | ...........................^
github.com/planetlabs/draino/internal/kubernetes.NewNodeLabelFilter.func1
	/Users/jenshausherr/src/draino/internal/kubernetes/nodefilters.go:62
github.com/planetlabs/draino/internal/kubernetes.TestNodeLabelFilter.func1
	/Users/jenshausherr/src/draino/internal/kubernetes/nodefilters_test.go:246
testing.tRunner
	/opt/homebrew/Cellar/go/1.17.1/libexec/src/testing/testing.go:1259
--- FAIL: TestNodeLabelFilter (0.00s)
    --- FAIL: TestNodeLabelFilter/AlsoPanics (0.00s)
panic: interface conversion: interface {} is nil, not bool [recovered]
	panic: interface conversion: interface {} is nil, not bool

goroutine 6 [running]:
testing.tRunner.func1.2({0x101502d60, 0x140004054a0})
	/opt/homebrew/Cellar/go/1.17.1/libexec/src/testing/testing.go:1209 +0x258
testing.tRunner.func1(0x140004301a0)
	/opt/homebrew/Cellar/go/1.17.1/libexec/src/testing/testing.go:1212 +0x284
panic({0x101502d60, 0x140004054a0})
	/opt/homebrew/Cellar/go/1.17.1/libexec/src/runtime/panic.go:1038 +0x21c
github.com/planetlabs/draino/internal/kubernetes.NewNodeLabelFilter.func1({0x1015f92e0, 0x14000249340})
	/Users/jenshausherr/src/draino/internal/kubernetes/nodefilters.go:64 +0x238
github.com/planetlabs/draino/internal/kubernetes.TestNodeLabelFilter.func1(0x140004301a0)
	/Users/jenshausherr/src/draino/internal/kubernetes/nodefilters_test.go:246 +0xc8
testing.tRunner(0x140004301a0, 0x1400000e918)
	/opt/homebrew/Cellar/go/1.17.1/libexec/src/testing/testing.go:1259 +0x104
created by testing.(*T).Run
	/opt/homebrew/Cellar/go/1.17.1/libexec/src/testing/testing.go:1306 +0x328
FAIL	github.com/planetlabs/draino/internal/kubernetes	0.403s
FAIL

{
	name: "ParseBoolean",
	obj: &core.Node{
		ObjectMeta: meta.ObjectMeta{
			Name:   nodeName,
			Labels: map[string]string{"metadata.labels.draino": "true"},
		},
	},
	expression:   "metadata.labels.draino == 'true'",
	passesFilter: true,
},

also fails:

Running tool: /opt/homebrew/bin/go test -timeout 30s -run ^TestNodeLabelFilter$ github.com/planetlabs/draino/internal/kubernetes

--- FAIL: TestNodeLabelFilter (0.00s)
    --- FAIL: TestNodeLabelFilter/ParseBoolean (0.00s)
        /Users/jenshausherr/src/draino/internal/kubernetes/nodefilters_test.go:236: 
            	Error Trace:	nodefilters_test.go:236
            	Error:      	Not equal: 
            	            	expected: true
            	            	actual  : false
            	Test:       	TestNodeLabelFilter/ParseBoolean
FAIL
FAIL	github.com/planetlabs/draino/internal/kubernetes	0.118s
FAIL