[MD settings] i18n template replacements in shared HTML resources

ui/base/template_expressions.cc

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/base/template_expressions.h"
 
 #include <stddef.h>
 
 #include "base/logging.h"
+#include "base/values.h"
 #include "net/base/escape.h"
 
 namespace {
 const char kLeader[] = "$i18n";
 const size_t kLeaderSize = arraysize(kLeader) - 1;
 const char kKeyOpen = '{';
 const char kKeyClose = '}';
 }  // namespace
 
 namespace ui {
 
+void TemplateReplacementsFromDictionaryValue(
+    const base::DictionaryValue& dictionary,
+    TemplateReplacements* replacements) {
+  for (base::DictionaryValue::Iterator it(dictionary); !it.IsAtEnd();
+       it.Advance()) {
+    if (it.value().IsType(base::Value::Type::STRING)) {
+      std::string str_value;
+      if (it.value().GetAsString(&str_value))
+        (*replacements)[it.key()] = str_value;
+    } else if (it.value().IsType(base::Value::Type::BOOLEAN)) {
+      bool bool_value;
+      if (it.value().GetAsBoolean(&bool_value))
+        TemplateReplacementsSetBool(it.key(), bool_value, replacements);
+    }
+  }
+}
+
+void TemplateReplacementsSetBool(const std::string& name,
+                                 bool value,
+                                 TemplateReplacements* replacements) {
+  // These are HTML Boolean attributes which are represented by their name
+  // if truthy and by complete absence (empty string) if falsy.

[Dan Beam, 2017/01/03 20:03:15]

this comment is confusing.

hidden="" hides stuff, and disabled="" disables.

https://jsfiddle.net/1ezdb6cs/

I think what you mean is that if setAttribute('blah', '') is called, a boolean
attribute is added (boolean attribute means no value).  if a value is processed
with a false value, we shouldn't be calling setAttribute().  as in, we should
drop a 2-liner into i18n_template_no_process.js after we've gotten the propName
and value:

if (value === false)
  continue;

and update any code that relies on this (i.e. CSS that looks for
=="true"/"false" or something).

https://cs.chromium.org/chromium/src/ui/webui/resources/js/i18n_template_no_p...

[dschuyler, 2017/01/03 20:36:56]

Correct, so in this case:

<div $i18n{guestMode}>...</div>

TemplateReplacementsSetBool("guestMode", true, ...) will add a guestMode
attribute and 

TemplateReplacementsSetBool("guestMode", false, ...) will not add a guestMode
attribute.

You make a good point about hidden and disabled though. Having a i18n tag of 
mplateReplacementsSetBool("hidden", true, ...) is not very specific (i.e. what's
being hidden).

For cases that need to be handled in JavaScript, the current loadTimeData will
continue to operate with actual true and false Boolean values.

+  (*replacements)[name] = value ? name : "";
+}
+
 std::string ReplaceTemplateExpressions(
     base::StringPiece source,
     const TemplateReplacements& replacements) {
   std::string formatted;
   const size_t kValueLengthGuess = 16;
   formatted.reserve(source.length() + replacements.size() * kValueLengthGuess);
   // Two position markers are used as cursors through the |source|.
   // The |current_pos| will follow behind |next_pos|.
   size_t current_pos = 0;
   while (true) {
@@ skipping 37 matching lines @@
     }
 
     formatted.append(replacement);
 
     current_pos = key_end + sizeof(kKeyClose);
   }
   return formatted;
 }
 
 }  // namespace ui