Fix frozen string literal warning in magic detection #123
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Tests pass on my machine and GH Actions, the Buildkite build erroring out seems unrelated and not fixable from this PR. |
simonbaird
reviewed
May 31, 2025
| @@ -119,7 +119,7 @@ def self.magic_match(io, method) | |||
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| io.binmode if io.respond_to?(:binmode) | |||
| io.set_encoding(Encoding::BINARY) if io.respond_to?(:set_encoding) | |||
| buffer = "".encode(Encoding::BINARY) | |||
| buffer = (+"").encode(Encoding::BINARY) | |||
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Perhaps this is better for readability:
Suggested change
| buffer = (+"").encode(Encoding::BINARY) | |
| buffer = String.new.encode(Encoding::BINARY) |
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I see from the bench-marking that you did already consider that option. Also this is more succinct hence better.
Suggested change
| buffer = (+"").encode(Encoding::BINARY) | |
| buffer = String.new(encoding: Encoding::BINARY) |
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I think what you want here is to declare a mutable string with binary encoding. That's
String.new(encoding: Encoding::BINARY)
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I’m not sure whether this actually fixes the issue I was trying to fix — tried to bundle install marcel from my repo and it still appeared — but this should still be a slight improvement |
simonbaird
added a commit
to tiddlyhost/tiddlyhost-com
that referenced
this pull request
Jun 2, 2025
As mentioned in the comments, rails/marcel#123 PR should make this go away. This is just for cosmetic reasons. The warning makes the test suite output look untidy.
sheldonh
reviewed
Jul 19, 2025
| @@ -119,7 +119,7 @@ def self.magic_match(io, method) | |||
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| io.binmode if io.respond_to?(:binmode) | |||
| io.set_encoding(Encoding::BINARY) if io.respond_to?(:set_encoding) | |||
| buffer = "".encode(Encoding::BINARY) | |||
| buffer = (+"").encode(Encoding::BINARY) | |||
There was a problem hiding this comment.
Suggested change
| buffer = (+"").encode(Encoding::BINARY) | |
| buffer = String.new(encoding: Encoding::BINARY) |
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With latest Ruby 3.4.x, using marcel emits the following warning:
lib/ruby/gems/3.4.0/gems/marcel-1.0.4/lib/marcel/magic.rb:120: warning: literal string will be frozen in the futureThis occurs because the code was creating an empty string literal used as mutable buffer for I/O operations.
This pull request replaces
"".dup.encode(Encoding::BINARY)with(+"").encode(Encoding::BINARY)in the buffer creation. Using the unary plus operator to explicitly create a mutable string benchmarked slightly faster than.dup.encode()on my local machine.Benchmark Results
String Creation Performance (1M iterations)
"".dup.encode()(+"").encode()String.new(encoding:)Memory Allocation (100K iterations)
"".dup.encode()(+"").encode()String.new(encoding:)Real-world Usage (10K magic detection operations)
"".dup.encode()(+"").encode()String.new(encoding:)