core: Allow refresh of local state with no resources

[dtolnay]

Fixes #4154 and fixes #5410.

HasResources is copied from @apparentlymart's work in #7026.

[dtolnay]

@jen20 Is there anything I can do to move this along?

[jen20]

We should probably verify that cached is not nil here since the HasResources() method accesses members.

[dtolnay]

HasResources returns false if the state is nil.

[jen20]

HI @dtolnay! Looks like we have a problem with the test applied to master:

--- FAIL: TestCacheState_RefreshState (0.01s)
panic: missing module path [recovered]
        panic: missing module path

goroutine 39 [running]:
panic(0x345f40, 0xc42021e050)
        /usr/local/Cellar/go/1.7/libexec/src/runtime/panic.go:500 +0x1a1
testing.tRunner.func1(0xc4201d4840)
        /usr/local/Cellar/go/1.7/libexec/src/testing/testing.go:579 +0x25d
panic(0x345f40, 0xc42021e050)
        /usr/local/Cellar/go/1.7/libexec/src/runtime/panic.go:458 +0x243
github.com/hashicorp/terraform/terraform.(*State).ModuleByPath(0xc420216960, 0x56bd10, 0x1, 0x1, 0xc420090838)
        /Users/James/Code/go/src/github.com/hashicorp/terraform/terraform/state.go:145 +0x1e2
github.com/hashicorp/terraform/terraform.(*State).init(0xc420216960)
        /Users/James/Code/go/src/github.com/hashicorp/terraform/terraform/state.go:580 +0x62
github.com/hashicorp/terraform/terraform.WriteState(0xc420216960, 0x553a40, 0xc420090a78, 0x0, 0x0)
        /Users/James/Code/go/src/github.com/hashicorp/terraform/terraform/state.go:1775 +0x51
github.com/hashicorp/terraform/state.(*LocalState).WriteState(0xc4201f1380, 0xc420216960, 0x0, 0x0)
        /Users/James/Code/go/src/github.com/hashicorp/terraform/state/local.go:69 +0x19c
github.com/hashicorp/terraform/state.(*CacheState).WriteState(0xc420051ec8, 0xc420216960, 0xc4201f1600, 0x3c)
        /Users/James/Code/go/src/github.com/hashicorp/terraform/state/cache.go:28 +0x41
github.com/hashicorp/terraform/state.TestCacheState_RefreshState(0xc4201d4840)
        /Users/James/Code/go/src/github.com/hashicorp/terraform/state/cache_test.go:91 +0x3f2
testing.tRunner(0xc4201d4840, 0x3fb5f8)
        /usr/local/Cellar/go/1.7/libexec/src/testing/testing.go:610 +0x81
created by testing.(*T).Run
        /usr/local/Cellar/go/1.7/libexec/src/testing/testing.go:646 +0x2ec
FAIL    github.com/hashicorp/terraform/state    0.044s

One of us will pick this up next week unless you get a chance to do so beforehand. Thanks!

[dtolnay]

I'm surprised it still merges cleanly after 2.5 months. I will let you folks take care of the test failure. I enabled the brand new "allow edits from maintainers" to make it easier.

[dtolnay]

Never mind, it was simple enough I fixed it myself.

[dtolnay]

git bisect points to #8120 as the point it started failing.

[zachgersh]

I would love to +1 this (can it be merged soonish) - just needed this today and thought terraform would work this way when it clearly does not.

[dtolnay]

@jen20 is there anything else I can do to help you merge this?

[ghost]

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