Make js.Build fully support modules

Fixes #7816
Fixes #7777
Fixes #7916

resources/jsconfig/jsconfig.go

@@ -0,0 +1,93 @@
+// Copyright 2020 The Hugo Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package jsconfig
+
+import (
+	"path/filepath"
+	"sort"
+	"sync"
+)
+
+// Builder builds a jsconfig.json file that, currently, is used only to assist
+// intellinsense in editors.
+type Builder struct {
+	sourceRootsMu sync.RWMutex
+	sourceRoots   map[string]bool
+}
+
+// NewBuilder creates a new Builder.
+func NewBuilder() *Builder {
+	return &Builder{sourceRoots: make(map[string]bool)}
+}
+
+// Build builds a new Config with paths relative to dir.
+// This method is thread safe.
+func (b *Builder) Build(dir string) *Config {
+	b.sourceRootsMu.RLock()
+	defer b.sourceRootsMu.RUnlock()
+
+	if len(b.sourceRoots) == 0 {
+		return nil
+	}
+	conf := newJSConfig()
+
+	var roots []string
+	for root := range b.sourceRoots {
+		rel, err := filepath.Rel(dir, filepath.Join(root, "*"))
+		if err == nil {
+			roots = append(roots, rel)
+		}
+	}
+	sort.Strings(roots)
+	conf.CompilerOptions.Paths["*"] = roots
+
+	return conf
+}
+
+// AddSourceRoot adds a new source root.
+// This method is thread safe.
+func (b *Builder) AddSourceRoot(root string) {
+	b.sourceRootsMu.RLock()
+	found := b.sourceRoots[root]
+	b.sourceRootsMu.RUnlock()
+
+	if found {
+		return
+	}
+
+	b.sourceRootsMu.Lock()
+	b.sourceRoots[root] = true
+	b.sourceRootsMu.Unlock()
+
+}
+
+// CompilerOptions holds compilerOptions for jsonconfig.json.
+type CompilerOptions struct {
+	BaseURL string              `json:"baseUrl"`
+	Paths   map[string][]string `json:"paths"`
+}
+
+// Config holds the data for jsconfig.json.
+type Config struct {
+	CompilerOptions CompilerOptions `json:"compilerOptions"`
+}
+
+func newJSConfig() *Config {
+	return &Config{
+		CompilerOptions: CompilerOptions{
+			BaseURL: ".",
+			Paths:   make(map[string][]string),
+		},
+	}
+}