cmd/govim: add config for defining the gopls environment

gopls can be configured with an environment, an environment which is
passed to go/packages. For example, setting GOOS and GOARCH, or setting
GOFLAGS=-tags=other to set a build tag.

Therefore we define a govim config key, "GoplsEnv", for setting this
environment.

For example:

  govim#config#Set("GoplsEnv", {"GOFLAGS": "-mod=readonly"})

As part of this add a test that verifies the behaviour of the above
setting. Setting of build tags does not current work; that is blocked on
golang/go#35548 and will be tested in a follow
up PR.

Fixes #555

autoload/govim/config.vim

@@ -104,6 +104,18 @@ function! s:validExperimentalTempModfile(v)
   return s:validBool(a:v)
 endfunction
 
+function! s:validGoplsEnv(v)
+  if type(a:v) != 4
+    return [v:false, "value must be a dict"]
+  endif
+  for [key, value] in items(a:v)
+    if type(value) != 1
+      return [v:false, "value for key ".key." must be a string"]
+    endif
+  endfor
+  return [v:true, ""]
+endfunction
+
 function! s:validExperimentalMouseTriggeredHoverPopupOptions(v)
   if has_key(a:v, "line")
     if type(a:v["line"]) != 0
@@ -135,6 +147,7 @@ let s:validators = {
       \ "GoImportsLocalPrefix": function("s:validGoImportsLocalPrefix"),
       \ "CompletionBudget": function("s:validCompletionBudget"),
       \ "ExperimentalTempModfile": function("s:validExperimentalTempModfile"),
+      \ "GoplsEnv": function("s:validGoplsEnv"),
       \ "ExperimentalMouseTriggeredHoverPopupOptions": function("s:validExperimentalMouseTriggeredHoverPopupOptions"),
       \ "ExperimentalCursorTriggeredHoverPopupOptions": function("s:validExperimentalCursorTriggeredHoverPopupOptions"),
       \ }

cmd/govim/config/config.go

@@ -120,6 +120,13 @@ type Config struct {
 	// Default: false
 	ExperimentalTempModfile *bool `json:",omitempty"`
 
+	// GoplsEnv configures the set of environment variables gopls is using in
+	// calls to go/packages. This is most easily understood in the context of
+	// build tags/constraints, where GOOS/GOARCH could be set for example, or
+	// GOFLAGS set to "-mod=readonly" in order to prevent changes being
+	// automatically made to go.mod.
+	GoplsEnv *map[string]string `json:",omitempty"`
+
 	// ExperimentalMouseTriggeredHoverPopupOptions is a map of options to apply
 	// when creating hover-based popup windows triggered by the mouse hovering
 	// over an identifier. It corresponds to the second argument to popup_create

cmd/govim/config/gen_applygen.go

@@ -37,6 +37,9 @@ func (r *Config) Apply(v *Config) {
 	if v.ExperimentalTempModfile != nil {
 		r.ExperimentalTempModfile = v.ExperimentalTempModfile
 	}
+	if v.GoplsEnv != nil {
+		r.GoplsEnv = v.GoplsEnv
+	}
 	if v.ExperimentalMouseTriggeredHoverPopupOptions != nil {
 		r.ExperimentalMouseTriggeredHoverPopupOptions = v.ExperimentalMouseTriggeredHoverPopupOptions
 	}

cmd/govim/gopls_client.go

@@ -25,6 +25,7 @@ const (
 	goplsCompletionBudget     = "completionBudget"
 	goplsTempModfile          = "tempModfile"
 	goplsVerboseOutput        = "verboseOutput"
+	goplsEnv                  = "env"
 )
 
 var _ protocol.Client = (*govimplugin)(nil)
@@ -155,6 +156,11 @@ func (g *govimplugin) Configuration(ctxt context.Context, params *protocol.Param
 	if os.Getenv(string(config.EnvVarGoplsVerbose)) == "true" {
 		goplsConfig[goplsVerboseOutput] = true
 	}
+	if g.vimstate.config.GoplsEnv != nil {
+		// It is safe not to copy the map here because a new config setting from
+		// Vim creates a new map.
+		goplsConfig[goplsEnv] = *conf.GoplsEnv
+	}
 	res[0] = goplsConfig
 
 	g.logGoplsClientf("Configuration response: %v", pretty.Sprint(res))

cmd/govim/internal/vimconfig/vimconfig.go

@@ -19,24 +19,26 @@ type VimConfig struct {
 	GoImportsLocalPrefix                         *string
 	CompletionBudget                             *string
 	ExperimentalTempModfile                      *int
+	GoplsEnv                                     *map[string]string
 	ExperimentalMouseTriggeredHoverPopupOptions  *map[string]interface{}
 	ExperimentalCursorTriggeredHoverPopupOptions *map[string]interface{}
 }
 
 func (c *VimConfig) ToConfig(d config.Config) config.Config {
 	v := config.Config{
-		FormatOnSave:                                 c.FormatOnSave,
-		QuickfixSigns:                                boolVal(c.QuickfixSigns, d.QuickfixSigns),
-		QuickfixAutoDiagnostics:                      boolVal(c.QuickfixAutoDiagnostics, d.QuickfixAutoDiagnostics),
-		HighlightDiagnostics:                         boolVal(c.HighlightDiagnostics, d.HighlightDiagnostics),
-		HoverDiagnostics:                             boolVal(c.HoverDiagnostics, d.HoverDiagnostics),
-		CompletionDeepCompletions:                    boolVal(c.CompletionDeepCompletions, d.CompletionDeepCompletions),
-		CompletionMatcher:                            c.CompletionMatcher,
-		Staticcheck:                                  boolVal(c.Staticcheck, d.Staticcheck),
-		CompleteUnimported:                           boolVal(c.CompleteUnimported, d.CompleteUnimported),
-		GoImportsLocalPrefix:                         stringVal(c.GoImportsLocalPrefix, d.GoImportsLocalPrefix),
-		CompletionBudget:                             stringVal(c.CompletionBudget, d.CompletionBudget),
-		ExperimentalTempModfile:                      boolVal(c.ExperimentalTempModfile, d.ExperimentalTempModfile),
+		FormatOnSave:              c.FormatOnSave,
+		QuickfixSigns:             boolVal(c.QuickfixSigns, d.QuickfixSigns),
+		QuickfixAutoDiagnostics:   boolVal(c.QuickfixAutoDiagnostics, d.QuickfixAutoDiagnostics),
+		HighlightDiagnostics:      boolVal(c.HighlightDiagnostics, d.HighlightDiagnostics),
+		HoverDiagnostics:          boolVal(c.HoverDiagnostics, d.HoverDiagnostics),
+		CompletionDeepCompletions: boolVal(c.CompletionDeepCompletions, d.CompletionDeepCompletions),
+		CompletionMatcher:         c.CompletionMatcher,
+		Staticcheck:               boolVal(c.Staticcheck, d.Staticcheck),
+		CompleteUnimported:        boolVal(c.CompleteUnimported, d.CompleteUnimported),
+		GoImportsLocalPrefix:      stringVal(c.GoImportsLocalPrefix, d.GoImportsLocalPrefix),
+		CompletionBudget:          stringVal(c.CompletionBudget, d.CompletionBudget),
+		ExperimentalTempModfile:   boolVal(c.ExperimentalTempModfile, d.ExperimentalTempModfile),
+		GoplsEnv:                  copyStringValMap(c.GoplsEnv, d.GoplsEnv),
 		ExperimentalMouseTriggeredHoverPopupOptions:  copyMap(c.ExperimentalMouseTriggeredHoverPopupOptions, d.ExperimentalMouseTriggeredHoverPopupOptions),
 		ExperimentalCursorTriggeredHoverPopupOptions: copyMap(c.ExperimentalCursorTriggeredHoverPopupOptions, d.ExperimentalCursorTriggeredHoverPopupOptions),
 	}
@@ -64,6 +66,21 @@ func stringVal(i, j *string) *string {
 	return i
 }
 
+func copyStringValMap(i, j *map[string]string) *map[string]string {
+	toCopy := i
+	if i == nil {
+		toCopy = j
+		if j == nil {
+			return nil
+		}
+	}
+	res := make(map[string]string)
+	for ck, cv := range *toCopy {
+		res[ck] = cv
+	}
+	return &res
+}
+
 func copyMap(i, j *map[string]interface{}) *map[string]interface{} {
 	toCopy := i
 	if i == nil {

cmd/govim/testdata/scenario_modreadonly/config_set_env_goflags_mod_readonly.txt

@@ -0,0 +1,66 @@
+# Test that calling govim#config#Set with a value for GoplsEnv of GOFLAGS
+# does the right thing. This will necessarily involve a number of checks
+# for the various build flags that can be set via GOFLAGS.
+
+[short] skip 'Skip short because we sleep for GOVIM_ERRLOGMATCH_WAIT to ensure we don''t have any errors'
+
+vim ex 'e main.go'
+vimexprwait pre.golden getqflist()
+vim ex 'w'
+
+# We have to sleep here because there is no event we are waiting for
+sleep $GOVIM_ERRLOGMATCH_WAIT
+
+# Verify go.mod has not changed
+cmp go.mod go.mod.golden.pre
+
+# Change go.mod from outside Vim
+exec go get example.com/blah@v1.0.0
+exec go mod tidy
+cmp go.mod go.mod.golden.post
+
+# Verify the diagnostic has been updated
+vimexprwait post.golden getqflist()
+
+# Disabled pending resolution to https://github.com/golang/go/issues/34103
+# errlogmatch -count=0 'LogMessage callback: &protocol\.LogMessageParams\{Type:(1|2), Message:".*'
+
+-- go.mod --
+module mod.com
+
+go 1.13
+-- go.mod.golden.pre --
+module mod.com
+
+go 1.13
+-- go.mod.golden.post --
+module mod.com
+
+go 1.13
+
+require example.com/blah v1.0.0
+-- main.go --
+package main
+
+import "example.com/blah"
+
+func main() {
+	println(blah.Name)
+}
+-- pre.golden --
+[
+  {
+    "bufnr": 1,
+    "col": 8,
+    "lnum": 3,
+    "module": "",
+    "nr": 0,
+    "pattern": "",
+    "text": "could not import example.com/blah (no package for import example.com/blah)",
+    "type": "",
+    "valid": 1,
+    "vcol": 0
+  }
+]
+-- post.golden --
+[]

cmd/govim/testdata/scenario_modreadonly/user_config.json

@@ -0,0 +1,3 @@
+{
+	"GoplsEnv": {"GOFLAGS": "-mod=readonly"}
+}