Disallow Ruby line comments that run all the way to the closing %> of an ERB tag, such as <%= foo # comment %>.
A comment inside a tag is allowed when it is followed by a newline inside the tag. ERB comment tags (<%# %>) are not affected. Tags that contain only a comment, such as <% # comment %>, are covered by erb-comment-syntax.
ERB and Erubi compile a template by appending the code of each tag to the generated Ruby source, followed by the code for the rest of the template. When a Ruby line comment runs up to the end of a tag, it also comments out that appended code, because it ends up on the same line. The result is a SyntaxError, or the rest of the template is silently dropped.
erb
<%= I18n.t("Hello") # comment%>
A Ruby comment at the end of an ERB tag also comments out the code that the template engine appends after the tag. Move the comment into a separate `<%# %>` tag, or put the closing `%>` on its own line. (erb-no-trailing-comment)
ruby
# The closing parenthesis is commented out, so this raises a SyntaxError_buf << ( I18n.t("Hello") # comment ).to_s;
erb
<% name= "World"# comment%>Hello, <%= name %>!
Local variable `name` is assigned but never used. Remove the assignment, or prefix it with an underscore as `_name` to show it is intentionally unused. (erb-no-unused-local-variable)
A Ruby comment at the end of an ERB tag also comments out the code that the template engine appends after the tag. Move the comment into a separate `<%# %>` tag, or put the closing `%>` on its own line. (erb-no-trailing-comment)
ruby
# The code is still valid, but "Hello, World!" is never renderedname = "World" # comment ; _buf << 'Hello, '.freeze; _buf << ( name ).to_s; _buf << '!'.freeze;
These offenses are reported as errors.
A <% %> tag that is the only thing on its line is the exception. Erubi trims such a line, so the line's trailing newline becomes part of the tag's code and ends the comment before the code that follows. This is how Rails compiles templates by default, so the template below renders correctly.
erb
<% if some_method %> Hello<% end# if some_method%>
Avoid Ruby comments at the end of ERB tags. This tag still renders correctly, but the comment breaks the template as soon as anything else is added to this line or the template is rendered by an engine that doesn't trim it. Move the comment into a separate `<%# %>` tag, or put the closing `%>` on its own line. (erb-no-trailing-comment)
Goodbye
ruby
# The newline after the comment ends it, so "Goodbye" is still renderedif some_method _buf << ' Hello'.freeze; end # if some_method _buf << 'Goodbye'.freeze;
The comment still breaks the template as soon as anything else is added to that line, and it breaks under an engine that doesn't trim the line. This rule reports these tags as warnings.
Herb::Engine handles trailing comments when it compiles a template. When template_engine is set to herb in .herb.yml, this rule reports every trailing comment as a warning, because none of them break rendering.
This rule provides an autofix that moves the comment into a separate <%# %> tag right after the original tag.
erb
<%= I18n.t("Hello") # comment%>
A Ruby comment at the end of an ERB tag also comments out the code that the template engine appends after the tag. Move the comment into a separate `<%# %>` tag, or put the closing `%>` on its own line. (erb-no-trailing-comment)
erb
<%= I18n.t("Hello") %><%# comment %>
The autofix is unsafe for a <% %> tag that is the only thing on its line. Erubi removes the indentation and trailing newline of such a line, but it doesn't do that for a line with two tags, so the rendered whitespace changes. For every other tag the line wasn't trimmed before the fix and isn't trimmed after it, so the autofix is safe.
The autofix is not applied to templates that have parse errors, such as <% if some_method # comment %><% end %>, or to tags that contain only a comment.
A Ruby comment at the end of an ERB tag also comments out the code that the template engine appends after the tag. Move the comment into a separate `<%# %>` tag, or put the closing `%>` on its own line. (erb-no-trailing-comment)
<% name = "World"# comment%>Hello, <%= name %>!
A Ruby comment at the end of an ERB tag also comments out the code that the template engine appends after the tag. Move the comment into a separate `<%# %>` tag, or put the closing `%>` on its own line. (erb-no-trailing-comment)
<% if some_method # comment%><% end %>
A Ruby comment at the end of an ERB tag also comments out the code that the template engine appends after the tag. Move the comment into a separate `<%# %>` tag, or put the closing `%>` on its own line. (erb-no-trailing-comment)
conditional_term: expected an `end` to close the conditional clause (`RUBY_PARSE_ERROR`) (parser-no-errors)
unexpected_token_close_context: unexpected end-of-input, assuming it is closing the parent top level context (`RUBY_PARSE_ERROR`) (parser-no-errors)
<% if some_method %> Hello<% end# if some_method%>
Avoid Ruby comments at the end of ERB tags. This tag still renders correctly, but the comment breaks the template as soon as anything else is added to this line or the template is rendered by an engine that doesn't trim it. Move the comment into a separate `<%# %>` tag, or put the closing `%>` on its own line. (erb-no-trailing-comment)
Linter Rule: Disallow Ruby comments at the end of ERB tags
Rule:
erb-no-trailing-commentDescription
Disallow Ruby line comments that run all the way to the closing
%>of an ERB tag, such as<%= foo # comment %>.A comment inside a tag is allowed when it is followed by a newline inside the tag. ERB comment tags (
<%# %>) are not affected. Tags that contain only a comment, such as<% # comment %>, are covered byerb-comment-syntax.Rationale
ERB and Erubi compile a template by appending the code of each tag to the generated Ruby source, followed by the code for the rest of the template. When a Ruby line comment runs up to the end of a tag, it also comments out that appended code, because it ends up on the same line. The result is a
SyntaxError, or the rest of the template is silently dropped.These offenses are reported as errors.
A
<% %>tag that is the only thing on its line is the exception. Erubi trims such a line, so the line's trailing newline becomes part of the tag's code and ends the comment before the code that follows. This is how Rails compiles templates by default, so the template below renders correctly.The comment still breaks the template as soon as anything else is added to that line, and it breaks under an engine that doesn't trim the line. This rule reports these tags as warnings.
Herb::Enginehandles trailing comments when it compiles a template. Whentemplate_engineis set toherbin.herb.yml, this rule reports every trailing comment as a warning, because none of them break rendering.Autofix
This rule provides an autofix that moves the comment into a separate
<%# %>tag right after the original tag.The autofix is unsafe for a
<% %>tag that is the only thing on its line. Erubi removes the indentation and trailing newline of such a line, but it doesn't do that for a line with two tags, so the rendered whitespace changes. For every other tag the line wasn't trimmed before the fix and isn't trimmed after it, so the autofix is safe.The autofix is not applied to templates that have parse errors, such as
<% if some_method # comment %><% end %>, or to tags that contain only a comment.Examples
✅ Good
🚫 Bad
⚠️ Warning
Configuration
This rule reports every trailing comment as a warning when the project renders its templates with
Herb::Engine:The rule's
severitysetting only applies to the offenses that break rendering. The other offenses are always reported as warnings.