Add css.TailwindCSS

Closes #12618
Closes #12620

1 files changed, 235 insertions, 0 deletions

diff --git a/resources/resource_transformers/cssjs/postcss.go b/resources/resource_transformers/cssjs/postcss.go
new file mode 100644
index 000000000..1a9e01142
--- /dev/null
+++ b/resources/resource_transformers/cssjs/postcss.go
@@ -0,0 +1,235 @@
+// Copyright 2024 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 cssjs provides resource transformations backed by some popular JS based frameworks.
+package cssjs
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"path/filepath"
+	"strings"
+
+	"github.com/gohugoio/hugo/common/collections"
+	"github.com/gohugoio/hugo/common/hexec"
+	"github.com/gohugoio/hugo/common/loggers"
+
+	"github.com/gohugoio/hugo/common/hugo"
+
+	"github.com/gohugoio/hugo/resources/internal"
+	"github.com/spf13/cast"
+
+	"github.com/mitchellh/mapstructure"
+
+	"github.com/gohugoio/hugo/common/herrors"
+	"github.com/gohugoio/hugo/resources"
+	"github.com/gohugoio/hugo/resources/resource"
+)
+
+// NewPostCSSClient creates a new PostCSSClient with the given specification.
+func NewPostCSSClient(rs *resources.Spec) *PostCSSClient {
+	return &PostCSSClient{rs: rs}
+}
+
+func decodePostCSSOptions(m map[string]any) (opts PostCSSOptions, err error) {
+	if m == nil {
+		return
+	}
+	err = mapstructure.WeakDecode(m, &opts)
+
+	if !opts.NoMap {
+		// There was for a long time a discrepancy between documentation and
+		// implementation for the noMap property, so we need to support both
+		// camel and snake case.
+		opts.NoMap = cast.ToBool(m["no-map"])
+	}
+
+	return
+}
+
+// PostCSSClient is the client used to do PostCSS transformations.
+type PostCSSClient struct {
+	rs *resources.Spec
+}
+
+// Process transforms the given Resource with the PostCSS processor.
+func (c *PostCSSClient) Process(res resources.ResourceTransformer, options map[string]any) (resource.Resource, error) {
+	return res.Transform(&postcssTransformation{rs: c.rs, optionsm: options})
+}
+
+type InlineImports struct {
+	// Service `mapstructure:",squash"`
+	// Enable inlining of @import statements.
+	// Does so recursively, but currently once only per file;
+	// that is, it's not possible to import the same file in
+	// different scopes (root, media query...)
+	// Note that this import routine does not care about the CSS spec,
+	// so you can have @import anywhere in the file.
+	InlineImports bool
+
+	// When InlineImports is enabled, we fail the build if an import cannot be resolved.
+	// You can enable this to allow the build to continue and leave the import statement in place.
+	// Note that the inline importer does not process url location or imports with media queries,
+	// so those will be left as-is even without enabling this option.
+	SkipInlineImportsNotFound bool
+}
+
+// Some of the options from https://github.com/postcss/postcss-cli
+type PostCSSOptions struct {
+	// Set a custom path to look for a config file.
+	Config string
+
+	NoMap bool // Disable the default inline sourcemaps
+
+	InlineImports `mapstructure:",squash"`
+
+	// Options for when not using a config file
+	Use         string // List of postcss plugins to use
+	Parser      string //  Custom postcss parser
+	Stringifier string // Custom postcss stringifier
+	Syntax      string // Custom postcss syntax
+}
+
+func (opts PostCSSOptions) toArgs() []string {
+	var args []string
+	if opts.NoMap {
+		args = append(args, "--no-map")
+	}
+	if opts.Use != "" {
+		args = append(args, "--use")
+		args = append(args, strings.Fields(opts.Use)...)
+	}
+	if opts.Parser != "" {
+		args = append(args, "--parser", opts.Parser)
+	}
+	if opts.Stringifier != "" {
+		args = append(args, "--stringifier", opts.Stringifier)
+	}
+	if opts.Syntax != "" {
+		args = append(args, "--syntax", opts.Syntax)
+	}
+	return args
+}
+
+type postcssTransformation struct {
+	optionsm map[string]any
+	rs       *resources.Spec
+}
+
+func (t *postcssTransformation) Key() internal.ResourceTransformationKey {
+	return internal.NewResourceTransformationKey("postcss", t.optionsm)
+}
+
+// Transform shells out to postcss-cli to do the heavy lifting.
+// For this to work, you need some additional tools. To install them globally:
+// npm install -g postcss-cli
+// npm install -g autoprefixer
+func (t *postcssTransformation) Transform(ctx *resources.ResourceTransformationCtx) error {
+	const binaryName = "postcss"
+
+	infol := t.rs.Logger.InfoCommand(binaryName)
+	infow := loggers.LevelLoggerToWriter(infol)
+
+	ex := t.rs.ExecHelper
+
+	var configFile string
+
+	options, err := decodePostCSSOptions(t.optionsm)
+	if err != nil {
+		return err
+	}
+
+	if options.Config != "" {
+		configFile = options.Config
+	} else {
+		configFile = "postcss.config.js"
+	}
+
+	configFile = filepath.Clean(configFile)
+
+	// We need an absolute filename to the config file.
+	if !filepath.IsAbs(configFile) {
+		configFile = t.rs.BaseFs.ResolveJSConfigFile(configFile)
+		if configFile == "" && options.Config != "" {
+			// Only fail if the user specified config file is not found.
+			return fmt.Errorf("postcss config %q not found", options.Config)
+		}
+	}
+
+	var cmdArgs []any
+
+	if configFile != "" {
+		infol.Logf("use config file %q", configFile)
+		cmdArgs = []any{"--config", configFile}
+	}
+
+	if optArgs := options.toArgs(); len(optArgs) > 0 {
+		cmdArgs = append(cmdArgs, collections.StringSliceToInterfaceSlice(optArgs)...)
+	}
+
+	var errBuf bytes.Buffer
+
+	stderr := io.MultiWriter(infow, &errBuf)
+	cmdArgs = append(cmdArgs, hexec.WithStderr(stderr))
+	cmdArgs = append(cmdArgs, hexec.WithStdout(ctx.To))
+	cmdArgs = append(cmdArgs, hexec.WithEnviron(hugo.GetExecEnviron(t.rs.Cfg.BaseConfig().WorkingDir, t.rs.Cfg, t.rs.BaseFs.Assets.Fs)))
+
+	cmd, err := ex.Npx(binaryName, cmdArgs...)
+	if err != nil {
+		if hexec.IsNotFound(err) {
+			// This may be on a CI server etc. Will fall back to pre-built assets.
+			return &herrors.FeatureNotAvailableError{Cause: err}
+		}
+		return err
+	}
+
+	stdin, err := cmd.StdinPipe()
+	if err != nil {
+		return err
+	}
+
+	src := ctx.From
+
+	imp := newImportResolver(
+		ctx.From,
+		ctx.InPath,
+		options.InlineImports,
+		t.rs.Assets.Fs, t.rs.Logger, ctx.DependencyManager,
+	)
+
+	if options.InlineImports.InlineImports {
+		var err error
+		src, err = imp.resolve()
+		if err != nil {
+			return err
+		}
+	}
+
+	go func() {
+		defer stdin.Close()
+		io.Copy(stdin, src)
+	}()
+
+	err = cmd.Run()
+	if err != nil {
+		if hexec.IsNotFound(err) {
+			return &herrors.FeatureNotAvailableError{
+				Cause: err,
+			}
+		}
+		return imp.toFileError(errBuf.String())
+	}
+
+	return nil
+}