schemas: compress schema files to reduce LS binary size

vsfsgen used GZIP compression by default but we abandoned it in favour of the stdlib embed package in #1070. This alone resulted in 80M binary size (compared to 18M before). Breaking down schemas to individual files would further increase binary size to 160M. In either case this is well over the limit of what we can pack into VSIX (VS Code extension) - currently 30MB.

Using gzip compression can bring the size to 19M. Mentioned sizes reflect darwin/arm64, but differences on other platforms should be similar.

internal/schemas/gen/gen.go

@@ -4,6 +4,8 @@
 package main
 
 import (
+	"bytes"
+	"compress/gzip"
 	"context"
 	"encoding/json"
 	"fmt"
@@ -200,9 +202,9 @@ func gen() error {
 					continue
 				}
 
-				log.Printf("%s: obtained schema for %s (%d bytes); terraform init: %s",
+				log.Printf("%s: obtained schema for %s (%db raw / %db compressed); terraform init: %s",
 					input.Provider.Addr.ForDisplay(), details.Version,
-					details.Size, details.InitElapsedTime)
+					details.RawSize, details.CompressedSize, details.InitElapsedTime)
 			}
 		}(i)
 	}
@@ -222,7 +224,8 @@ type Inputs struct {
 
 type Outputs struct {
 	Version         string
-	Size            int64
+	RawSize         int
+	CompressedSize  int64
 	InitElapsedTime time.Duration
 }
 
@@ -358,15 +361,24 @@ func schemaForProvider(ctx context.Context, client registry.Client, input Inputs
 		return nil, err
 	}
 
-	f, err := os.Create(filepath.Join(dataDir, "schema.json"))
+	f, err := os.Create(filepath.Join(dataDir, "schema.json.gz"))
 	if err != nil {
 		return nil, fmt.Errorf("failed to create schema file: %w", err)
 	}
-
-	err = json.NewEncoder(f).Encode(ps)
+	var rawJson bytes.Buffer
+	err = json.NewEncoder(&rawJson).Encode(ps)
 	if err != nil {
 		return nil, fmt.Errorf("failed to encode schema file: %w", err)
 	}
+	gzw := gzip.NewWriter(f)
+	_, err = gzw.Write(rawJson.Bytes())
+	if err != nil {
+		return nil, fmt.Errorf("failed to write compressed file: %w", err)
+	}
+	err = gzw.Close()
+	if err != nil {
+		return nil, fmt.Errorf("failed to close compressed file: %w", err)
+	}
 
 	fi, err := f.Stat()
 	if err != nil {
@@ -375,7 +387,8 @@ func schemaForProvider(ctx context.Context, client registry.Client, input Inputs
 
 	return &Outputs{
 		Version:         pVersion.String(),
-		Size:            fi.Size(),
+		RawSize:         rawJson.Len(),
+		CompressedSize:  fi.Size(),
 		InitElapsedTime: initElapsed,
 	}, nil
 }

internal/schemas/schemas.go

@@ -1,10 +1,13 @@
 package schemas
 
 import (
+	"compress/gzip"
 	"embed"
 	"errors"
 	"fmt"
+	"io"
 	"io/fs"
+	"log"
 	"path"
 
 	"github.com/hashicorp/go-version"
@@ -15,7 +18,7 @@ import (
 var FS embed.FS
 
 type ProviderSchema struct {
-	File    fs.File
+	File    io.Reader
 	Version *version.Version
 }
 
@@ -44,7 +47,7 @@ func FindProviderSchemaFile(filesystem fs.ReadDirFS, pAddr tfaddr.Provider) (*Pr
 
 	rawVersion := entries[0].Name()
 
-	filePath := path.Join(providerPath, rawVersion, "schema.json")
+	filePath := path.Join(providerPath, rawVersion, "schema.json.gz")
 	file, err := filesystem.Open(filePath)
 	if err != nil {
 		return nil, err
@@ -55,8 +58,14 @@ func FindProviderSchemaFile(filesystem fs.ReadDirFS, pAddr tfaddr.Provider) (*Pr
 		return nil, err
 	}
 
+	gzipReader, err := gzip.NewReader(file)
+	if err != nil {
+		return nil, err
+	}
+	log.Printf("unzipped file at %s", filePath)
+
 	return &ProviderSchema{
-		File:    file,
+		File:    gzipReader,
 		Version: version,
 	}, nil
 }