@bfwk/expression-completion

Expression Editor

The Expression Editor is a general purpose editor/validator for expressions defined by an ANTLR grammar and with input contexts described by JSON Schema.

The grammar (in 232) is a small initial subset of the existing expression grammar (Formula.g4). In order to use a grammar for code completion it is useful to inject various rules to facilitate the discovery of a token's scope wrt completion.

This uses the Javascript ANTLR4 runtime.

Development

The build:dev target includes a code generation step, based upon the grammar (Expression.g4), to create various grammar specific source files in a non-repository gen/ directory. The code generator is Java-based and saved in the repository in the bin/ directory. Directions for running the code generator are available on the ANTLR site.

Do NOT checkin changes to the grammar without rebuilding and testing - the generated sources might be altered, and might become incompatible with the other source files.

Future Directions

As the grammar is expanded in subsequent releases we might want to consider the use of this code completion engine. This was not used in 232 because of difficulties rolling up the Typescript ANTLR4 runtime upon which it depends. An early cut using this is available on the branch https://git.soma.salesforce.com/BuilderFramework/builder-framework/tree/drobertson/DO-NOT-DELETE-typescript-completion-engine