internal/filetypes: rename top level "tags" field

When reviewing this code, I was struck by the ambiguity between the
top level `tags` field and the `build.File.Tags` field (also encoded as
a `tags` field in CUE), and it wasn't immediately obvious that the
top level `tags` field didn't play a role in the latter. It doesn't,
so make that clearer by renaming it to something that's
clearly distinct.

Signed-off-by: Roger Peppe <rogpeppe@gmail.com>
Change-Id: I7356d940634dfd05a40295e62c937e60f2874b5a
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/1200761
Unity-Result: CUE porcuepine <cue.porcuepine@gmail.com>
Reviewed-by: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: CUEcueckoo <cueckoo@cuelang.org>

internal/filetypes/filetypes.go

@@ -320,7 +320,7 @@ func parseType(scope string, mode Mode) (modeVal, fileVal cue.Value, _ error) {
 			if ok {
 				fileVal = fileVal.FillPath(cue.MakePath(cue.Str("tags"), cue.Str(tagName)), tagVal)
 			} else {
-				info := typesValue.LookupPath(cue.MakePath(cue.Str("tags"), cue.Str(tag)))
+				info := typesValue.LookupPath(cue.MakePath(cue.Str("tagInfo"), cue.Str(tag)))
 				if !info.Exists() {
 					return cue.Value{}, cue.Value{}, errors.Newf(token.NoPos, "unknown filetype %s", tag)
 				}

internal/filetypes/types.cue

@@ -26,6 +26,7 @@ package build
 	encoding!:       #Encoding
 	interpretation?: #Interpretation
 	form?:           #Form
+	// Note: tags includes values for non-boolean tags only.
 	tags?: [string]: string
 }
 
@@ -162,23 +163,23 @@ modes: [string]: {
 	// extensions maps a file extension to its associated default file properties.
 	extensions: {
 		// "":           _
-		".cue":       tags.cue
-		".json":      tags.json
-		".jsonl":     tags.jsonl
-		".ldjson":    tags.jsonl
-		".ndjson":    tags.jsonl
-		".yaml":      tags.yaml
-		".yml":       tags.yaml
-		".toml":      tags.toml
-		".txt":       tags.text
-		".go":        tags.go
-		".wasm":      tags.binary
-		".proto":     tags.proto
-		".textproto": tags.textproto
-		".textpb":    tags.textproto // perhaps also pbtxt
+		".cue":       tagInfo.cue
+		".json":      tagInfo.json
+		".jsonl":     tagInfo.jsonl
+		".ldjson":    tagInfo.jsonl
+		".ndjson":    tagInfo.jsonl
+		".yaml":      tagInfo.yaml
+		".yml":       tagInfo.yaml
+		".toml":      tagInfo.toml
+		".txt":       tagInfo.text
+		".go":        tagInfo.go
+		".wasm":      tagInfo.binary
+		".proto":     tagInfo.proto
+		".textproto": tagInfo.textproto
+		".textpb":    tagInfo.textproto // perhaps also pbtxt
 
 		// TODO: jsonseq,
-		// ".pb":        tags.binpb // binarypb
+		// ".pb":        tagInfo.binpb // binarypb
 	}
 
 	// encodings: "": error("no encoding specified")
@@ -327,8 +328,8 @@ interpretations: pb: {
 	stream: true
 }
 
-// tags maps command line tags to file properties.
-tags: {
+// tagInfo maps command line tags to file properties.
+tagInfo: {
 	schema: form: "schema"
 	graph: form:  "graph"
 	dag: form:    "dag"