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https://issues.apache.org/jira/browse/GROOVY-12445?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18129428#comment-18129428
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ASF GitHub Bot commented on GROOVY-12445:
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daniellansun opened a new pull request, #2972:
URL: https://github.com/apache/groovy/pull/2972
https://issues.apache.org/jira/browse/GROOVY-12445
> STC: refuse unknown SignatureCodec versions without reading payload bytes
> -------------------------------------------------------------------------
>
> Key: GROOVY-12445
> URL: https://issues.apache.org/jira/browse/GROOVY-12445
> Project: Groovy
> Issue Type: Improvement
> Reporter: Daniel Sun
> Priority: Major
>
> h2. Context
> {{@TypeChecked}} stores an inferred method return type on bytecode as
> {{@TypeChecked.TypeCheckingInfo}}. The annotation has two members:
> * {{version}} — an {{int}}, default {{0}}
> * {{inferredType}} — a Base64 string
> The protocol version is that {{version}} member. The payload string has no
> version byte, magic number, or extra length prefix. This release implements
> version {{1}} only. {{SignatureCodecFactory.getCodec(int)}} returns
> {{SignatureCodecVersion1}} for {{1}}, and {{null}} for every other {{int}}:
> the annotation default {{0}}, any negative value, and {{2}} or higher.
> h2. Problem
> The {{SignatureCodec}} Javadoc said the encoded string itself must carry a
> version so later Groovy releases can decode older payloads. That puts the
> version in the wrong place and invites a reader to parse bytes whose layout
> it does not implement.
> On the write path, {{addTypeCheckingInfoAnnotation}} called
> {{codec.encode(...)}} with no null check. A {{null}} codec would throw
> {{NullPointerException}}.
> On the read path there was no helper that treated a {{null}} codec as "there
> is no inferred signature". Feeding an unknown version to the version-1 codec,
> or decoding anyway, would throw or invent a type from bytes that belong to
> another layout. Two experimental compilers may use the same unpublished
> version {{int}} for different layouts. A release compiler refuses those
> payloads the same way it refuses a higher version it does not implement.
> h2. Contract
> A {{null}} codec means there is no inferred signature. The caller uses the
> method's declared return type. The payload string is left unread.
> ||Version||getCodec||Read path||
> |{{1}}|{{SignatureCodecVersion1}}|decode {{inferredType}}|
> |{{0}}, negative, or {{2}} and higher|{{null}}|declared return type; payload
> unread|
> A version {{int}} that has shipped in a release is append-only: one {{int}}
> keeps one layout. A later codec that claims an older version still decodes
> that older version. The version stays a single {{int}} on the annotation.
> {{getCodec}} continues to return {{null}} for an unimplemented version. The
> write path returns before {{encode}} when the codec is {{null}}.
> {code:java}
> static ClassNode inferredReturnOrDeclared(int version, String signature,
> ClassLoader loader, ClassNode declared) {
> SignatureCodec codec = getCodec(version, loader);
> if (codec == null) {
> return declared;
> }
> return codec.decode(signature);
> }
> {code}
> {{addTypeCheckingInfoAnnotation}} currently has no production callers
> (disconnected under GROOVY-6401). There is also no production reader of
> {{@TypeCheckingInfo}} today. Locking the unknown-version rule now means a
> later reader uses the declared return type for any version this compiler does
> not implement.
> h2. Touch points
> * {{org.codehaus.groovy.transform.stc.SignatureCodec}} — protocol Javadoc
> * {{StaticTypeCheckingVisitor.addTypeCheckingInfoAnnotation}} — return when
> the codec is {{null}}
> * {{SignatureCodecFactory.inferredReturnOrDeclared}} — decode helper
> *
> {{src/test/groovy/org/codehaus/groovy/transform/stc/SignatureCodecTest.groovy}}
> h2. Scope
> This issue covers the unknown-version rule only. Union payload layout,
> rewiring {{addTypeCheckingInfoAnnotation}} onto {{startMethodInference}}, and
> a new compiler diagnostic are separate work.
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