internal/lsp/cache: correctly split env vars

We were using strings.Split on env vars, which did bad stuff when the
var contained an =, e.g. GOFLAGS=-tags=foo. Only split on the first =.

Irritatingly, this breaks only `go mod` commands, so almost nothing in
gopls failed, just organize imports and the `go.mod` code lens stuff.

Fixes #38669

Change-Id: I8d28c806b77a8df92100af1fa4fbcca5edf97cff
Reviewed-on: https://go-review.googlesource.com/c/tools/+/230560
Run-TryBot: Heschi Kreinick <[email protected]>
TryBot-Result: Gobot Gobot <[email protected]>
Reviewed-by: Rebecca Stambler <[email protected]>

Author: heschi

internal/lsp/cache/view.go

@@ -373,7 +373,7 @@ func (v *view) buildProcessEnv(ctx context.Context) (*imports.ProcessEnv, error)
 		}
 	}
 	for _, kv := range env {
-		split := strings.Split(kv, "=")
+		split := strings.SplitN(kv, "=", 2)
 		if len(split) < 2 {
 			continue
 		}

internal/lsp/regtest/diagnostics_test.go

@@ -245,7 +245,7 @@ func TestHello(t *testing.T) {
 }
 `
 
-func Test_Issue38267(t *testing.T) {
+func TestIssue38267(t *testing.T) {
 	runner.Run(t, testPackage, func(t *testing.T, env *Env) {
 		env.OpenFile("lib_test.go")
 		env.Await(
@@ -330,7 +330,7 @@ func TestMissingDependency(t *testing.T) {
 	})
 }
 
-func TestAdHocPackagesIssue_36951(t *testing.T) {
+func TestAdHocPackages_Issue36951(t *testing.T) {
 	const adHoc = `
 -- b/b.go --
 package b
@@ -345,7 +345,7 @@ func Hello() {
 	})
 }
 
-func TestNoGOPATHIssue_37984(t *testing.T) {
+func TestNoGOPATH_Issue37984(t *testing.T) {
 	const missingImport = `
 -- main.go --
 package main
@@ -362,3 +362,24 @@ func _() {
 		}
 	}, WithEnv("GOPATH="))
 }
+
+func TestEqualInEnv_Issue38669(t *testing.T) {
+	const missingImport = `
+-- go.mod --
+module mod.com
+
+-- main.go --
+package main
+
+var _ = x.X
+-- x/x.go --
+package x
+
+var X = 0
+`
+	runner.Run(t, missingImport, func(t *testing.T, env *Env) {
+		env.OpenFile("main.go")
+		env.OrganizeImports("main.go")
+		env.Await(EmptyDiagnostics("main.go"))
+	}, WithEnv("GOFLAGS=-tags=foo"))
+}