Step one towards stable error messages with details:

pkg/polymer/lib/src/build/messages.dart

Index: pkg/polymer/lib/src/build/messages.dart
diff --git a/pkg/polymer/lib/src/build/messages.dart b/pkg/polymer/lib/src/build/messages.dart
new file mode 100644
index 0000000000000000000000000000000000000000..36b13e089dc2f81a78673cab95b925efae5ca1f5
--- /dev/null
+++ b/pkg/polymer/lib/src/build/messages.dart
@@ -0,0 +1,528 @@
+// Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+/// Contains all error and warning messages produced by polymer.
+library polymer.src.build.messages;
+
+import 'package:code_transformers/messages/messages.dart';
+import 'constants.dart';
+
+const importNotFound = const MessageTemplate(
+    const MessageId('polymer', 1),
+    'couldn\'t find imported asset "%-path-%" in package "%-package-%".',
+    'Import not found',
+    '''
+An HTML import seems to be broken. This could be because the file doesn't exist
+or because the link URL is incorrect.
+''');
+
+const duplicateDefinition = const MessageTemplate(
+    const MessageId('polymer', 2),
+    'duplicate definition for custom tag "%-name-%".%-second-%',
+    'Duplicate definition',
+    '''
+Custom element names are global and can only be defined once. Some common
+reasons why you might get two definitions:
+
+  * There are two different elements defined with the same name.

[Kathy Walrath, 2014/09/03 21:26:55]

There are two -> Two
defined with -> have [or "are defined that have" or "are defined with"]

[Siggi Cherem (dart-lang), 2014/09/04 02:32:16]

went with option 4: `are declared with` :)

+  * A single HTML file defining an element, is imported from two different

[Kathy Walrath, 2014/09/03 21:26:55]

, is imported from -> has been imported using

[Siggi Cherem (dart-lang), 2014/09/04 02:32:17]

Done.

+    URLs.
+''');
+
+const usePolymerHtmlMessage = const MessageTemplate(
+    const MessageId('polymer', 3),
+      'Missing definition for <polymer-element>, please add the following '
+      'HTML import at the top of this file: <link rel="import" '
+      'href="%-reachOutPrefix-%packages/polymer/polymer.html">.',
+      'Missing import to polymer.html',
+      '''
+Starting with polymer 0.11.0 we require that each file that uses the definition

[Kathy Walrath, 2014/09/03 21:26:54]

0.11.0 we require that each -> 0.11.0, each

[Siggi Cherem (dart-lang), 2014/09/04 02:32:18]

Done.

+of polymer-element has to import it either directly or transitively.

[Kathy Walrath, 2014/09/03 21:26:54]

has to import -> must import

[Siggi Cherem (dart-lang), 2014/09/04 02:32:15]

Done.

+''');
+
+const noImportWithinElement = const MessageTemplate(
+    const MessageId('polymer', 4),
+    'Polymer.dart\'s implementation of '
+    'HTML imports are not supported within polymer element definitions, yet. '
+    'Please move the import out of this <polymer-element>.',

[Kathy Walrath, 2014/09/03 21:26:53]

Please move -> Move

[Siggi Cherem (dart-lang), 2014/09/04 02:32:17]

Pretty please? :)

I'm actually curious: since this is an error on the command line, would users
appreciate to hear the magic words?

[Kathy Walrath, 2014/09/04 17:07:28]

I suppose "Please" isn't bad here. We don't usually use it in docs because it
hides the action. But if people are truly annoyed, "please" can't hurt.

+    'Can\'t use imports inside <polymer-element>',
+    '''
+HTML imports are expected on the top of each document, outside of any

[Kathy Walrath, 2014/09/03 21:26:53]

on the -> at the

[Siggi Cherem (dart-lang), 2014/09/04 02:32:15]

Done.

+polymer-element definitions. The polymer build process combines all your HTML
+files together so you can deploy a single HTML file with your application. This
+build process will ignore imports that appear to be in the wrong location.

[Kathy Walrath, 2014/09/03 21:26:54]

will ignore -> ignores

[Siggi Cherem (dart-lang), 2014/09/04 02:32:15]

Done.

+''');
+
+const useInitDart = const MessageTemplate(
+    const MessageId('polymer', 5),
+    'To run a polymer application, you need to call "initPolymer". You can '

[Kathy Walrath, 2014/09/03 21:26:55]

"initPolymer" -> initPolymer()

[Siggi Cherem (dart-lang), 2014/09/04 02:32:17]

Done.

+    'either include a generic script tag that does this for you:'
+    '\'<script type="application/dart">export "package:polymer/init.dart";'
+    '</script>\' or add your own script tag and call that function. '
+    'Make sure the script tag is placed after all HTML imports.',
+    'Missing init.dart',
+    '''
+We determined that your application entry point didn't have any Dart script

[Kathy Walrath, 2014/09/03 21:26:55]

->
Your application entrypoint doesn't have...

[Siggi Cherem (dart-lang), 2014/09/04 02:32:15]

Done.

+tags, and hence, it's missing some initialization needed for polymer.dart.

[Kathy Walrath, 2014/09/03 21:26:54]

->tags, so it's...

[Siggi Cherem (dart-lang), 2014/09/04 02:32:16]

Done.

+''');
+
+const noDartScriptAndExperimental = const MessageTemplate(
+    const MessageId('polymer', 6),
+    'The experimental bootstrap feature doesn\'t support script tags on '
+    'the main document (for now).',
+    'No script tags with experimental bootstrap.',

[Kathy Walrath, 2014/09/03 21:26:55]

Remove the "."

[Siggi Cherem (dart-lang), 2014/09/04 02:32:16]

Done.

+    'This experimental feature is no longer supported.');
+
+const onlyOneTag = const MessageTemplate(
+    const MessageId('polymer', 7),
+    'Only one "application/dart" script tag per document is allowed.',
+    'Single tag per document',

[Kathy Walrath, 2014/09/03 21:26:55]

Most of these are phrased to describe the problem, not the solution. Maybe:

Multiple Dart script tags found

[Siggi Cherem (dart-lang), 2014/09/04 02:32:17]

Done.

+    '''
+Dartium currently limits to have a single script tag per document. Any

[Kathy Walrath, 2014/09/03 21:26:55]

limits to have a single
->
allows only one

[Siggi Cherem (dart-lang), 2014/09/04 02:32:16]

Done.

+additional script tags might be ignored or result in an error. This will
+likely change in the future, but for now, we recommend that you combine the
+script tags together into a single Dart library.
+''');
+
+const moveHtmlImportsUp = const MessageTemplate(
+    const MessageId('polymer', 8),
+    'Move HTML imports above your Dart script tag.',
+    'Imports before script tags',
+    '''
+It is good practice to put all your HTML imports at the beginning of the
+document, above any Dart script tags. Today, the execution of Dart script tags
+is not synchronous in Dartium, so the difference is not noticeable. However, we
+are planning changes in Dartium that will eventually make the timing of script
+tags execution match how they are in Javascript. At that point the order of your
+imports with respect to script tags will be important. Following the practice of
+putting imports first protects your app from a future breaking change in this
+respect.
+''');
+
+const missingHref = const MessageTemplate(
+    const MessageId('polymer', 9),
+    'link rel="%-rel-%" missing href.',
+    'Missing href on a `<link>` tag',
+    'All `<link>` tags should have a valid URL to a resource.');
+
+const elementWasDeprecatedEonsAgo = const MessageTemplate(
+    const MessageId('polymer', 10),
+    '<element> elements are not supported, use <polymer-element> instead',
+    '`<element>` is deprecated',
+    '''
+Long ago `<polymer-element>` used to be called `<element>`. You probably ran
+into this error if you were migrating code that was written on a very early
+version of polymer.
+''');
+
+// TODO(jmesserly): this warning is wrong if someone is using raw custom
+// elements. Is there another way we can handle this warning that won't
+// generate false positives?
+const customElementNotFound = const MessageTemplate(
+    const MessageId('polymer', 11),
+    'custom element with name "%-tag-%" not found.',
+    'Definition of a custom element not found',
+    '''
+The polymer build was not able to find the definition of a custom element. This
+can happen if an element is defined with a `<polymer-element>` tag, but you are
+missing an HTML import or the import link is incorrect.
+
+This warning can also be a false alarm. For instance, when an element is defined
+programatically using `document.registerElement`. In that case the polymer build
+will not be able to see the definition and will produce this warning.
+''');
+
+const scriptTagSeemsEmpty = const MessageTemplate(
+    const MessageId('polymer', 12),
+    'script tag seems empty.',
+    'Empty script tag',
+    'Script tags should either have a `src` attribute or a non-empty body.');
+
+const wrongScriptTypeExpectedDart = const MessageTemplate(
+    const MessageId('polymer', 13),
+    'Wrong script type, expected type="application/dart".',
+    'Expected Dart mime-type',
+'''
+You seem to have a `.dart` extension on a script tag, but the mime-type
+doesn't match `application/dart`.
+''');
+
+const wrongFileTypeExpectedDart = const MessageTemplate(
+    const MessageId('polymer', 14),
+    '"application/dart" scripts should use the .dart file extension.',
+    'Expected Dart file extension',
+'''
+You are using the `application/dart` mime-type on a script tag, so we expected
+the URL to the script source URL to have a `.dart` extension, but it doesn't.
+''');
+
+const foundBothScriptSrcAndBody = const MessageTemplate(
+    const MessageId('polymer', 15),
+    'script tag has "src" attribute and also has script text.',
+    'Script tags should have either a URL or an inlined body.',

[Kathy Walrath, 2014/09/03 21:26:54]

->
Script with both src and inline text

(be sure to remove the ".")

[Siggi Cherem (dart-lang), 2014/09/04 02:32:16]

Done.

+'''
+You have a script tag that includes both a `src` attribute, and script text

[Kathy Walrath, 2014/09/03 21:26:54]

attribute,...
->
attribute and inline script text.

[Siggi Cherem (dart-lang), 2014/09/04 02:32:17]

Done.

+inlined. You must choose one or the other.
+''');
+
+const incorrectInstantiationMissingBaseTag = const MessageTemplate(
+    const MessageId('polymer', 16),
+    'custom element "%-tag-%" extends from "%-base-%", but '
+    'this tag will not include the default properties of "%-base-%". '
+    'To fix this, either write this tag as <%-base-% '
+    'is="%-tag-%"> or remove the "extends" attribute from '
+    'the custom element declaration.',
+    'Incorrect instantiation: missing base tag in instantiation.',

[Kathy Walrath, 2014/09/03 21:26:54]

remove the "."

[Siggi Cherem (dart-lang), 2014/09/04 02:32:16]

Done.

+    '''
+When you declare that a custom element extends from a base tag, for example:
+
+    <polymer-element name="my-example" extends="ul">
+
+or:
+
+    <polymer-element name="my-example2" extends="ul">
+    <polymer-element name="my-example" extends="my-example2">
+
+You should instantiate `my-example` by using this syntax:
+
+    <ul is="my-example">
+
+And not:
+
+    <my-example>
+
+Only elements that don't extend from existing HTML elements are created using
+the latter form.
+
+This is because browsers first create the base element, and then upgrade them to

[Kathy Walrath, 2014/09/03 21:26:55]

them -> it

[Siggi Cherem (dart-lang), 2014/09/04 02:32:15]

Done.

+have the extra functionality of your custom element. In the example above, using
+`<ul>` tells the browser what is the base type that they need to create before
+doing the upgrade.

[Kathy Walrath, 2014/09/03 21:26:53]

what is the base type that they need to create
->
which base type it must create

[Siggi Cherem (dart-lang), 2014/09/04 02:32:16]

Done.

+''');
+
+const incorrectInstantiationBogusBaseTag = const MessageTemplate(
+    const MessageId('polymer', 17),
+    'custom element "%-tag-%" doesn\'t declare any type '
+    'extensions. To fix this, either rewrite this tag as '
+    '<%-tag-%> or add \'extends="%-base-%"\' to '
+    'the custom element declaration.',
+
+    'Incorrect instantiation: extra `is` attribute or missing `extends` '
+    'in declaration.',

[Kathy Walrath, 2014/09/03 21:26:55]

remove the "."

[Siggi Cherem (dart-lang), 2014/09/04 02:32:16]

Done.

+    '''
+Creating a custom element using the syntax:
+
+    <ul is="my-example">
+
+means that the declaration of `my-example` extends transitively from `ul`. This
+error message is shown if the definition of `my-example` doesn't declare this
+extension. It might be that you no longer extend from the base element, in which
+case the fix is to change the instantiation to:
+
+    <my-example>
+
+or that the declaration needs to be fixed and include the `extends` attribute,

[Kathy Walrath, 2014/09/03 21:26:54]

or that ->
Another possibility is that

and include -> to include

[Siggi Cherem (dart-lang), 2014/09/04 02:32:17]

Done.

+for example:
+
+    <polymer-element name="my-example" extends="ul">
+''');
+
+const incorrectInstantiationWrongBaseTag = const MessageTemplate(
+    const MessageId('polymer', 18),
+    'custom element "%-tag-%" extends from "%-base-%". '
+    'Did you mean to write <%-base-% is="%-tag-%">?',
+    'Incorrect instantiation: base tag seems wrong',
+    '''
+It seems you have a declaration like:
+
+    <polymer-element name="my-example" extends="div">
+
+but an instantiation like:
+
+    <span is="my-example">
+
+Both the declaration and the instantiation need to match on the base type. So
+either the instantiation needs to be fixed to be more like:
+
+    <span is="my-example">
+
+or the declaration should be fixed to be like:
+
+    <polymer-element name="my-example" extends="span">
+''');
+
+const noDashesInCustomAttributes = const MessageTemplate(
+    const MessageId('polymer', 19),
+    'PolymerElement no longer recognizes attribute names with '
+    'dashes such as "%-name-%". Use %-alternative-% '
+    'instead (both forms are equivalent in HTML).',
+    'No dashes allowed in custom attributes',
+    '''
+Polymer used to recognize attributes with dashes like `my-name` and convert them
+to match properties where dashes were removed, and words follow the camelCase
+style (for example `myName`). This feature is no longer available. Now simply
+use the same name as the property.
+
+Because HTML attributes are case-insensitive, you can also write the name of
+your property entirely in lowercase. Just be sure that your custom-elements
+don't declare two properties with the same name but different capitalization.
+''');
+
+
+const eventHandlersOnlyWithinPolymerElements = const MessageTemplate(
+    const MessageId('polymer', 20),
+    'Inline event handlers are only supported inside '
+    'declarations of <polymer-element>.',
+    'Event handlers not supported here',
+    '''
+Bindings of the form `{{ }}` are supported inside `<template>` nodes, even outside
+of `<polymer-element>` declarations. However, those bindings only support binding
+values into the content of a node or an attribute.
+
+Inline event handlers of the form `on-click="{{method}}"` are a special feature
+of polymer elements, so they are only supported inside `<polymer-element>`
+definitions.
+''');
+
+const invalidEventHandlerBody = const MessageTemplate(
+    const MessageId('polymer', 21),
+    'Invalid event handler body "%-value-%". Declare a method '
+    'in your custom element "void handlerName(event, detail, target)" '
+    'and use the form %-name-%="{{handlerName}}".',
+    'Event handler bindings are method names, not expressions.',

[Kathy Walrath, 2014/09/03 21:26:53]

remove the "." and make it not a sentence. Maybe:

No expressions allowed in event handler bindings

[Siggi Cherem (dart-lang), 2014/09/04 02:32:15]

Done.

+    '''
+Unlike data bindings, event handler bindings of the form `on-click="{{method}}"`
+are not evaluated as expressions. They are meant to just contain a simple name
+that resolves to a method in your polymer element's class definition.
+''');
+
+const nestedPolymerElementDefinitionsNotAllowed = const MessageTemplate(
+    const MessageId('polymer', 22),
+    'Nested polymer element definitions are not allowed.',
+    'Nested polymer element definitions are not allowed.',

[Kathy Walrath, 2014/09/03 21:26:55]

Nested polymer element definitions not allowed

(removing the verb and the ".")

[Siggi Cherem (dart-lang), 2014/09/04 02:32:17]

Done.

+    '''
+Because custom element names are global, there is no need to have a
+`<polymer-element>` defined nested within a `<polymer-element>`. If you have a

[Kathy Walrath, 2014/09/03 21:26:53]

defined -> definition?

[Siggi Cherem (dart-lang), 2014/09/04 02:32:17]

Done.

+definition inside another, please move the sencond definition out.

[Kathy Walrath, 2014/09/03 21:26:53]

please move -> move
sencond -> second

[Siggi Cherem (dart-lang), 2014/09/04 02:32:15]

Done.

+
+It's possible that you see this error if you have an HTML import within a

[Kathy Walrath, 2014/09/03 21:26:55]

It's possible that you -> You might

[Siggi Cherem (dart-lang), 2014/09/04 02:32:16]

Done.

+polymer element. You should be able to also move the import out of the element

[Kathy Walrath, 2014/09/03 21:26:54]

to also -> to

[Siggi Cherem (dart-lang), 2014/09/04 02:32:17]

Done.

+definition.
+''');
+
+const missingTagName = const MessageTemplate(
+    const MessageId('polymer', 23),
+    'Missing tag name of the custom element. Please include an '

[Kathy Walrath, 2014/09/03 21:26:55]

Please include -> Include

[Siggi Cherem (dart-lang), 2014/09/04 02:32:17]

Done.

+    'attribute like \'name="your-tag-name"\'.',
+    'Polymer element definitions must have a name.',

[Kathy Walrath, 2014/09/03 21:26:55]

->
Polymer element definition without a name

[Siggi Cherem (dart-lang), 2014/09/04 02:32:17]

Done.

+    '''
+Polymer element definitions must have a name. You can include a name by using
+the `name` attribute in `<polymer-element>` for example:
+
+    <polymer-element name="my-example">
+''');
+
+final invalidTagName = new MessageTemplate(
+    const MessageId('polymer', 24),
+    'Invalid name "%-name-%". Custom element names must have '
+    'at least one dash and can\'t be any of the following names: '

[Kathy Walrath, 2014/09/03 21:26:54]

dash -> dash (-)

[Siggi Cherem (dart-lang), 2014/09/04 02:32:15]

Done.

+    '${invalidTagNames.keys.join(", ")}.',
+    'Custom element names must have a dash.',

[Kathy Walrath, 2014/09/03 21:26:53]

->
Custom element name missing a dash

[Siggi Cherem (dart-lang), 2014/09/04 02:32:15]

Done.

+    '''
+Custom element names must have a dash and can\'t be any of the following

[Kathy Walrath, 2014/09/03 21:26:55]

dash -> dash (`-`)

[Siggi Cherem (dart-lang), 2014/09/04 02:32:17]

Done.

+reserved names:
+
+${invalidTagNames.keys.map((e) => '  * `$e`\n').join('')}
+
+''');
+
+final inlineImportFail = const MessageTemplate(
+    const MessageId('polymer', 25),
+    'Failed to inline html import: %-error-%',

[Kathy Walrath, 2014/09/03 21:26:54]

html -> HTML

[Siggi Cherem (dart-lang), 2014/09/04 02:32:17]

Done.

+    'An error occurred while iniling an import',

[Kathy Walrath, 2014/09/03 21:26:54]

iniling -> inlining

[Siggi Cherem (dart-lang), 2014/09/04 02:32:16]

wow - this typo has been there for months!

+    '''
+An error occurred while iniling an import in the polymer build. This is often
+the result of a broken HTML import.
+''');
+
+final inlineStyleFail = const MessageTemplate(
+    const MessageId('polymer', 26),
+    'Failed to inline stylesheet: %-error-%',
+    'An error occurred while iniling a stylesheet.',

[Kathy Walrath, 2014/09/03 21:26:55]

->
Error while inlining a stylesheet

(remove the verb and the ".", fix the spelling of inlining)

[Siggi Cherem (dart-lang), 2014/09/04 02:32:17]

Done.

+    '''
+An error occurred while iniling a stylesheet in the polymer build. This is often

[Kathy Walrath, 2014/09/03 21:26:53]

GLOBAL:
iniling -> inlining

[Siggi Cherem (dart-lang), 2014/09/04 02:32:15]

Done.

+the result of a broken URL in a `<link rel="stylesheet" href="...">`.
+''');
+
+final scriptFileNotFound = const MessageTemplate(
+    const MessageId('polymer', 27),
+    'Script file at "%-url-%" not found.',
+    'URL to a script file might be incorrect',
+    '''
+An error occurred trying to read a script tag on a given URL. This is often the
+result of a broken URL in a `<script src="...">`.
+''');
+
+final useUnderscorePrefix = const MessageTemplate(
+    const MessageId('polymer', 28),
+    'When using bindings with the "%-name-%" attribute you may '
+    'experience errors in certain browsers. Please use the '
+    '"_%-name-%" attribute instead.',
+    'Not all browsers support bindings to URL attributes',

[Kathy Walrath, 2014/09/03 21:26:53]

This message seems more specific than the previous string indicates. They should
either both cover URLs or not be so specific to URLs. Maybe:

'Attribute missing "_" prefix'

[Siggi Cherem (dart-lang), 2014/09/04 02:32:16]

Done

+    '''
+Not all browsers support bindings to URL attributes. Some browsers might

[Kathy Walrath, 2014/09/03 21:26:55]

Delete the first sentence if it just repeats the message. Also, doesn't this
apply to _style and _value, as well as _src and _href?

[Siggi Cherem (dart-lang), 2014/09/04 02:32:15]

Well well well - you just found a bug in the linter :) We were assuming it was
only for URL attributes, not also for value or style. That's why the message was
tailored to URL attributes. We didn't mention URL in the error itself because
the attribute was mentioned already explicitly (%-name-%)

I rephrase it slightly. I kept the first sentence though, because now the title
doesn't include that anymore.

+sanitize the attributes and result in an incorrect link. For this reason polymer
+provides a special set of attributes that let you bypass any browser internal
+attribute validation. The name of the attribute is the same as the original
+attribute, but with a leading underscore. For example, instead of writing:
+
+    <img src="{{binding}}">
+
+you can write:
+
+    <img _src="{{binding}}">
+
+For more information, see <http://goo.gl/5av8cU>.
+''');
+
+final dontUseUndercorePrefix = const MessageTemplate(
+    const MessageId('polymer', 29),
+    'The "_%-name-%" attribute is only supported when using bindings. '
+    'Please change to the "%-name-%" attribute.',
+    'The special underscore attribute is only for bindings.',

[Kathy Walrath, 2014/09/03 21:26:54]

->
Attribute has "_" prefix'

[Siggi Cherem (dart-lang), 2014/09/04 02:32:15]

Done.

+    '''
+A special attribute exists to support bindings on URL attributes. For example,
+this correctly binds the `src` attribute in an image:
+
+    <img _src="{{binding}}">
+
+However, this special `_src` attribute is only available for bindings. If you
+just have a URL, use the normal `src` attribute instead.
+''');
+
+final internalErrorDontKnowHowToImport = const MessageTemplate(
+    const MessageId('polymer', 30),
+    "internal error: don't know how to include %-target-% from"
+    " %-source-%.%-extra-%",
+    "Internal error: don't know how to include a URL",
+    '''
+Sorry, you just run into a bug in the polymer transformer code. Please file a

[Kathy Walrath, 2014/09/03 21:26:54]

you just run -> you just ran
[GLOBAL]

[Siggi Cherem (dart-lang), 2014/09/04 02:32:16]

Done.

+bug at <http://dartbug.com/new> including if possible some example code that can

[Kathy Walrath, 2014/09/03 21:26:55]

including if possible some
->
including, if possible, some
[GLOBAL]

[Siggi Cherem (dart-lang), 2014/09/04 02:32:17]

Done.

+help us reproduce the issue so we can investigate.

[Kathy Walrath, 2014/09/03 21:26:54]

delete " so we can investigate"

[Siggi Cherem (dart-lang), 2014/09/04 02:32:16]

Done.

+''');
+
+final internalErrorUnexpectedScript = const MessageTemplate(
+    const MessageId('polymer', 31),
+    'unexpected script. The ScriptCompactor transformer should run after '
+    'running the ImportInliner',
+    'Internal error: phases run out of order',
+    '''
+Sorry, you just run into a bug in the polymer transformer code. Please file a
+bug at <http://dartbug.com/new> including if possible some example code that can
+help us reproduce the issue so we can investigate.
+''');
+
+final noPrivateCustomTag = const MessageTemplate(
+    const MessageId('polymer', 32),
+    '@CustomTag is not currently supported on private classes:'
+    ' %-name-%. Consider making this class public, or create a '
+    'public initialization method marked with `@initMethod` that calls '
+    '`Polymer.register(%-name-%, %-className-%)`.',
+    '`@CustomTag` is only supported on public classes.',

[Kathy Walrath, 2014/09/03 21:26:54]

->
`@CustomTag` used on a private class

[Siggi Cherem (dart-lang), 2014/09/04 02:32:16]

Done.

+    '''
+The `@CustomTag` annotation is currently only supported on public classes. If
+you need to register a custom element whose implementation is a private class,

[Kathy Walrath, 2014/09/03 21:26:53]

Maybe clarify that it's private because its name starts with a _ or its
library/package names starts with _? Otherwise, Java programmers will think they
have to add "public".

[Siggi Cherem (dart-lang), 2014/09/04 02:32:16]

added, but I'm not convinced this is the right place to educate about it. Maybe
there is a link about private vs public classes in our docs we can include here?

+you can still do so by invoking `Polymer.register` within a public method marked
+with `@initMethod`.
+''');
+
+final noPrivateInitMethod = const MessageTemplate(
+    const MessageId('polymer', 33),
+    '@initMethod is no longer supported on private functions: %-name-%',
+    '`@initMethod` is only supported on public functions.',

[Kathy Walrath, 2014/09/03 21:26:55]

->
`@initMethod` used on a private function

[Siggi Cherem (dart-lang), 2014/09/04 02:32:16]

Done.

+    '''
+The `@initMethod` annotation is currently only supported on public top-level
+functions.
+''');
+
+final missingArgumentInAnnotation = const MessageTemplate(
+    const MessageId('polymer', 34),
+    'Missing argument in @%-name-% annotation',
+    'Missing argument in annotation',
+    'The annotation expects one argument, but the argument was not provided.');
+
+final invalidArgumentInAnnotation = const MessageTemplate(
+    const MessageId('polymer', 35),
+    'The parameter to @%-name-% seems to be invalid.',
+    'Invalid argument in annotation',

[Kathy Walrath, 2014/09/03 21:26:54]

->
Non-constant argument in annotation

[Siggi Cherem (dart-lang), 2014/09/04 02:32:15]

Kept as "invalid" because we don't know that the problem was that it was a
non-constant :-/

+    '''
+We expected a constant argument in an annotation, but the polymer build was not

[Kathy Walrath, 2014/09/03 21:26:55]

->
The polymer transformer was not able to extract a constant value for the
annotation argument.
This can happen...

(getting rid of "we", plus "build" implies pub build to me, but it could be pub
serve, no? but maybe you really didn't mean the transformer?)

[Siggi Cherem (dart-lang), 2014/09/04 02:32:17]

Done.

+able to extract the value of this argument. This can happen if your code is
+currently in a state that can't be analyzed (for example, it has parse
+errors) or if the expression passed as an argument is invalid (for example, it
+is not a compile-time constant).
+''');
+
+
+final noInitializersError = const MessageTemplate(
+    const MessageId('polymer', 36),
+    'No polymer initializers were found. Make sure to either '
+    'annotate your polymer elements with @CustomTag or include a '
+    'top level method annotated with @initMethod that registers your '
+    'elements. Both annotations are defined in the polymer library ('
+    'package:polymer/polymer.dart).',
+    'No polymer initializers found',
+    '''
+No polymer initializers were found. Make sure to either 
+annotate your polymer elements with @CustomTag or include a 
+top level method annotated with @initMethod that registers your 
+elements. Both annotations are defined in the polymer library (
+package:polymer/polymer.dart).
+''');
+
+final noEventBindingsWithAtExpression = const MessageTemplate(
+    const MessageId('polymer', 37),
+    'event bindings with @ are no longer supported',
+    'Event bindings with @ are no longer supported',
+    '''
+For a while there was an undocumented feature that allowed users to include
+expressions in event bindings using the `@` prefix, for example:
+
+    <div on-click="{{@a.b.c}}">
+    
+This feature is no longer supported.
+''');
+
+final noPrivateEventHandlers = const MessageTemplate(
+    const MessageId('polymer', 38),
+    'private symbols cannot be used in event handlers',
+    'Private symbols cannot be used in event handlers',

[Kathy Walrath, 2014/09/03 21:26:53]

->
Private symbol in event handler

[Siggi Cherem (dart-lang), 2014/09/04 02:32:15]

Done.

+    '''
+Currently private members can't be used on event handlers. So you can't write:

[Kathy Walrath, 2014/09/03 21:26:53]

on -> as? with? for?

[Siggi Cherem (dart-lang), 2014/09/04 02:32:16]

in? :) 

+
+    <div on-click="{{_method}}">
+
+This restriction might be removed in the future, but for now, you need to make
+your event handlers public.
+''');
+
+final noPrivateSymbolsInBinding = const MessageTemplate(
+    const MessageId('polymer', 39),
+    'private symbols are not supported',
+    'Private symbols are not supported',

[Kathy Walrath, 2014/09/03 21:26:53]

->
Private symbol in a binding expression

[Siggi Cherem (dart-lang), 2014/09/04 02:32:17]

Done.

+    '''
+Private members can't be used on binding expressions. For example, you can't
+write:
+
+    <div>{{a.b._c}}</div>
+''');
+
+final html5Warning = const MessageTemplate(
+    const MessageId('polymer', 40),
+    '(from html5lib) %-message-%',
+    'A warning was found while parsing the html document',

[Kathy Walrath, 2014/09/03 21:26:54]

html -> HTML
[global within text]

[Siggi Cherem (dart-lang), 2014/09/04 02:32:15]

Done.

+    '''
+We use a parser that implements the HTML5 spec (`html5lib`). We report any

[Kathy Walrath, 2014/09/03 21:26:53]

We use a
->
The polymer transformer uses a

We report -> This message reports

that were detected by our....
->
that the parser detects.

[Siggi Cherem (dart-lang), 2014/09/04 02:32:15]

Done.

+warnings that were detected by our parser during the polymer build process.
+''');