See http://dev.clojure.org/display/design/Reader+Conditionals for design.

The implementation details contain several major parts:

1) LispReader changes to implement new conditional read syntax and features.

In RT:

• suppress-read - new dynamic var

• readString() - new arity that takes opts

In LispReader:

• read(...) entry point - added new variants that take opts. The opts-only form will decode :eof into the correct values for eofIsError and eofValue. Internal forms take both opts and pendingForms (list).

• All reader invoke dispatch methods now take both opts and pendingForms which get drug around the call stack.

• Defined all option keys and well-known allowed values - OPT_EOF, OPT_FEATURES, OPT_READ_COND, EOFTHROW, PLATFORM_KEY, PLATFORM_FEATURES, COND_ALLOW, COND_PRESERVE.

• read(...) entry point will ensure installation of {:features #{:clj}}, appropriately merging others or none. There is no path that will pass :features inside Clojure but users can call LispReader with it directly.

• readDelimitedList() was refactored so it can share logic with readCondDelimited().

• Luke can provide more detail on the guts of reader conditional reading if needed.

New ReaderConditional and TaggedLiteral types.

In clojure.core:

• tagged-literal?, tagged-literal, reader-conditional?, reader-conditional - new functions to support the preserved data form of these

• new print-method impls for TaggedLiteral and ReaderConditional

• read - added new arity that takes opts and explain opts in docstring

• read-string - added new arity that takes opts (placement matches edn/read-string and is designed for partial application)

2) cljc file changes.
In Compiler:

• OPTS_COND_ALLOWED - keep around a map {:read-cond :allow} to invoke reader when reading .cljc files.

• readerOpts() - new private function to determine reader options to use based on file name (.clj vs .cljc)

• load() - use readerOpts() and invoke LispReader with them

• compile() - use readerOpts() and invoke LispReader with them

In RT:

• load(...) - check first for .clj file, then for .cljc file when looking by ns

In clojure.main - update code to allow for .clj and .cljc files
In clojure.repl - update code to allow for .clj and .cljc files

3) Tests + infrastructure updates.

• Move test/clojure/test_clojure/reader.clj to test/clojure/test_clojure/reader.cljc so that we can test reader conditionals.

• Bump version of test.generative to get newer version that depends on newer tools.namespace which is able to find .cljc files as source files. The test script at src/script/run_test.clj uses this to find Clojure test files and without the bump, it will not find the new reader.cljc test ns. Note: if you use the ant build, you need to re-run antsetup.sh for this to take effect.

• src/script/run_test.clj - as part of the version bump, move from deprecated namespace to new namespace

• Added lots of tests in reader.cljc

Patch: clj-1424-12.patch

Screened by:

Related: CLJS-27, TRDR-14