FHIRPath

Use this when working in helios-fhirpath, helios-fhirpath-support, the FHIRPath CLI, or the FHIRPath HTTP server.

CLI Usage

# Basic expression evaluation
cargo run --bin fhirpath-cli -- -e "Patient.name.family" -r patient.json

# With context expression
cargo run --bin fhirpath-cli -- -c "Patient.name" -e "family" -r patient.json

# With variables
cargo run --bin fhirpath-cli -- -e "value > %threshold" -r observation.json --var threshold=5.0

# Parse debug tree, no resource needed
cargo run --bin fhirpath-cli -- -e "Patient.name.given.first()" --parse-debug-tree

# Read from stdin
cat patient.json | cargo run --bin fhirpath-cli -- -e "Patient.name.family" -r -

# Specify FHIR version
cargo run --bin fhirpath-cli -- --fhir-version R5 -e "Patient.name.family" -r patient.json

HTTP Server

The FHIRPath server is compatible with fhirpath-lab.

# Start with defaults, port 3000
cargo run --bin fhirpath-server

# Custom configuration
FHIRPATH_SERVER_PORT=8080 FHIRPATH_SERVER_HOST=0.0.0.0 cargo run --bin fhirpath-server

Method	URL	Description
POST	/	Evaluate FHIRPath and auto-detect FHIR version
POST	/r4, /r4b, /r5, /r6	Version-specific evaluation
GET	/health	Health check

Environment

Variable	Default	Description
FHIRPATH_SERVER_PORT	3000	Server port
FHIRPATH_SERVER_HOST	127.0.0.1	Host to bind
FHIRPATH_LOG_LEVEL	info	Log level
FHIRPATH_ENABLE_CORS	true	Enable CORS
FHIRPATH_CORS_ORIGINS	*	Allowed origins
FHIRPATH_MAX_BODY_SIZE	10485760	Max request body size in bytes, measured after decompression
FHIRPATH_TERMINOLOGY_SERVER	none	Terminology server URL

Request bodies with gzip, deflate, br, or zstd Content-Encoding are decompressed before parsing. Unsupported encodings return 415. Responses are compressed when the client sends Accept-Encoding.

Tests

• FHIRPath test cases live under crates/fhirpath/tests/.
• Official FHIR test cases come from the fhir-test-cases repository.
• Test expressions independently with fhirpath-cli before debugging broader server behavior.