Robonito · SDE II, Engineering Team

Nested Parser and Interpolation Engine

Built an nested expression parser and interpolation engine to resolve variables, invoke random data generators, and fetch values from external data sources for data-driven automation flows.

The Challenge

Automation flows needed a way to resolve variables, generate random data, and read from spreadsheets or CSV files, while also supporting nested expressions for complex operations.

Engineering Approach

Defined a custom expression syntax where {{!var_name}} resolved to a runtime variable value, {{$function_name}} invoked a generator function, and {{@datasource.sheet_name.col_name[row_start,row_end]}} read from tabular data sources.
Implemented random data helpers such as {{$random_name}} and {{$random_email}} to support data-driven flows without hardcoding values.
Built an extended parser that could interpret nested expressions, like {{$random_{{!var_name}}}}, so that dynamic values could be composed at runtime.
Added an evaluator that applied parsed values in the correct order so variables, functions, and datasource lookups were resolved consistently.
Supported spreadsheet and CSV-backed inputs so test flows could pull structured data from external files during execution.

Impact

Enabled expressive runtime interpolation for complex automation flows that needed dynamic inputs from variables, functions, and external data sources.
Made the engine more reusable for data-driven scenarios by supporting nested expressions and a uniform evaluation model across input types.