Aryan Ganjoo created TEXT-243:
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Summary: StringSubstitutorReader.skip advances the template, not
the substituted output
Key: TEXT-243
URL: https://issues.apache.org/jira/browse/TEXT-243
Project: Commons Text
Issue Type: Bug
Reporter: Aryan Ganjoo
h3. Observed
{{StringSubstitutorReader}} inherits {{FilterReader.skip(long)}}, which skips
characters in the wrapped template reader rather than in the substituted
output. For example, with template {{${v}Z}} and {{v = abc}}, {{skip(1)}}
reports one skipped character but the next output is {{{v}Z}} instead of
{{bcZ}}. Buffered output and substitutions that contract the stream also give
incorrect skip positions or counts.
h3. Expected
{{skip(n)}} should consume up to {{n}} characters of the stream returned by
this reader, consistent with the {{Reader.skip}} contract. It should not call
{{skip}} on the wrapped template reader.
h3. Reproduction and validation
A local test using {{new StringSubstitutorReader(new StringReader("${v}Z"), new
StringSubstitutor(Collections.singletonMap("v", "abc")))}} reproduces the
mismatch. The affected production code is unchanged on current Commons Text
master {{f5bec9dd7becc3a20f3e949fb2391456a94611c3}}. An earlier pristine-source
regression run had 10 failures among 14 new cases. A local corrected candidate
passes 18 focused skip tests and the default Maven build (2,007 tests, zero
failures/errors, three skips); a separate independent read-only review found no
concrete P1/P2 issue. Java 8, hosted CI, and downstream usage were not tested.
h3. Possible fix
Implement {{skip(long)}} by consuming the substituted output through this
reader’s {{read}} path, and reject use after the wrapper is closed. This is a
local candidate, not a submitted PR. AI assistance was used for discovery, test
and patch preparation, and validation.
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