Handle KaTeX warnings

Fixes #13735

Author: bep

hugolib/site.go

@@ -204,6 +204,7 @@ func NewHugoSites(cfg deps.DepsCfg) (*HugoSites, error) {
 				// Katex is relatively slow.
 				PoolSize: 8,
 				Infof:    logger.InfoCommand("wasm").Logf,
+				Warnf:    logger.WarnCommand("wasm").Logf,
 			},
 		),
 	}

internal/warpc/js/common.js

@@ -4,6 +4,15 @@ export function readInput(handle) {
 	let currentLine = [];
 	const buffer = new Uint8Array(buffSize);
 
+	// These are not implemented by QuickJS.
+	console.warn = (value) => {
+		console.log(value);
+	};
+
+	console.error = (value) => {
+		throw new Error(value);
+	};
+
 	// Read all the available bytes
 	while (true) {
 		// Stdin file descriptor

internal/warpc/js/greet.bundle.js

@@ -7,6 +7,14 @@ const render = function (input) {
 	const expression = data.expression;
 	const options = data.options;
 	const header = input.header;
+	header.warnings = [];
+
+	if (options.strict == 'warn') {
+		// By default, KaTeX will write to console.warn, that's a little hard to handle.
+		options.strict = (errorCode, errorMsg, token) => {
+			header.warnings.push(`katex: ${errorCode}: ${errorMsg} at ${token}`);
+		};
+	}
 	// Any error thrown here will be caught by the common.js readInput function.
 	const output = katex.renderToString(expression, options);
 	writeOutput({ header: header, data: { output: output } });

internal/warpc/js/renderkatex.bundle.js

@@ -51,6 +51,9 @@ type Header struct {
 
 	// Set in the response if there was an error.
 	Err string `json:"err"`
+
+	// Warnings is a list of warnings that may be returned in the response.
+	Warnings []string `json:"warnings,omitempty"`
 }
 
 type Message[T any] struct {
@@ -155,6 +158,14 @@ func (p *dispatcherPool[Q, R]) Execute(ctx context.Context, q Message[Q]) (Messa
 	}
 
 	resp, err := call.response, p.Err()
+	if len(resp.Header.Warnings) > 0 {
+		for _, w := range resp.Header.Warnings {
+			if w != "" {
+				p.opts.Warnf("%s", w)
+			}
+		}
+	}
+
 	if err == nil && resp.Header.Err != "" {
 		err = errors.New(resp.Header.Err)
 	}
@@ -270,6 +281,8 @@ type Options struct {
 
 	Infof func(format string, v ...any)
 
+	Warnf func(format string, v ...any)
+
 	// E.g. quickjs wasm. May be omitted if not needed.
 	Runtime Binary
 
@@ -325,6 +338,7 @@ type dispatcherPool[Q, R any] struct {
 	counter     atomic.Uint32
 	dispatchers []*dispatcher[Q, R]
 	close       func() error
+	opts        Options
 
 	errc  chan error
 	donec chan struct{}
@@ -355,6 +369,11 @@ func newDispatcher[Q, R any](opts Options) (*dispatcherPool[Q, R], error) {
 			// noop
 		}
 	}
+	if opts.Warnf == nil {
+		opts.Warnf = func(format string, v ...any) {
+			// noop
+		}
+	}
 
 	if opts.Memory <= 0 {
 		// 32 MiB
@@ -466,6 +485,7 @@ func newDispatcher[Q, R any](opts Options) (*dispatcherPool[Q, R], error) {
 
 	dp := &dispatcherPool[Q, R]{
 		dispatchers: make([]*dispatcher[Q, R], len(inOuts)),
+		opts:        opts,
 
 		errc:  make(chan error, 10),
 		donec: make(chan struct{}),

internal/warpc/js/renderkatex.js

@@ -536,3 +536,21 @@ disableKinds = ['page','rss','section','sitemap','taxonomy','term']
 	b, err = hugolib.TestE(t, f)
 	b.Assert(err.Error(), qt.Contains, "invalid strict mode")
 }
+
+// Issue 13735.
+func TestToMathStrictModeWarn(t *testing.T) {
+	t.Parallel()
+
+	files := `
+-- hugo.toml --
+disableKinds = ['page','rss','section','sitemap','taxonomy','term']
+-- layouts/all.html --
+{{ transform.ToMath "a %" (dict "strict" "warn") }}
+-- foo --
+`
+
+	b := hugolib.Test(t, files, hugolib.TestOptWarn())
+
+	b.AssertLogMatches("commentAtEnd")
+	b.AssertFileContent("public/index.html", `<annotation encoding="application/x-tex">a %</annotation>`)
+}