fix(engine): template dict key collision and workflow.input for-each source#21
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jrob5756 merged 3 commits intomicrosoft:mainfrom Mar 5, 2026
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Jinja2's default attribute resolution tries Python getattr() before dict key lookup. When a dict has a key named 'items' (or 'keys', 'values', etc.), getattr(d, 'items') returns the dict.items method instead of d['items'] (the stored value). Filters like '| length' then call len() on the method object, producing: Template rendering failed: object of type 'builtin_function_or_method' has no len() Fix: Subclass Jinja2 Environment with _DictSafeEnvironment that prefers dict key lookup over attribute access for dict objects. This resolves the collision for any field name that matches a dict method. Also rename the 'items' output field in for-each-simple.yaml to 'topics' to avoid the confusing collision in the example.
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Add _resolve_workflow_input_array to handle workflow.input.* references in for-each source fields, with automatic JSON string parsing for CLI --input values. Update for-each-simple.yaml to accept optional --input items array with fallback to agent-generated topics when not provided. Add 9 tests covering workflow.input source resolution.
Shazwazza
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jrob5756
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Mar 5, 2026
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Summary
Two related fixes for the workflow engine: a template rendering bug when dictionary keys shadow Python built-in methods, and missing support for
workflow.input.*references in for-each source fields.Changes
Fix template rendering error when dict keys shadow built-in methods
Dictionary outputs with keys like
"items","values", or"keys"causedAttributeErrorduring Jinja2 template rendering becauseTemplateRenderer._flatten_to_namespaceresolved these to the dict's built-in methods instead of the actual values.dict.__getitem__access in_flatten_to_namespaceto bypass method shadowingitems,values,keys,get, andupdateas dict keysSupport
workflow.input.*as for-each sourceThe docs and examples referenced
source: workflow.input.itemsfor for-each groups, but_resolve_array_referenceonly resolved paths fromagent_outputs, causing a runtime error._resolve_workflow_input_arrayhelper to resolveworkflow.input.*paths fromcontext.workflow_inputs--inputpasses arrays as strings like'["a","b"]')Update
for-each-simple.yamlexampleitemsas an optional input parameteritem_finderagent now conditionally passes through provided items or generates random topicsconductor run examples/for-each-simple.yaml --input items='["apple", "banana", "cherry"]' conductor run examples/for-each-simple.yaml