fix: Change PaymentCurrencyAmount.value type from float to string

[dinstein]

Summary

The value field in PaymentCurrencyAmount is currently defined as a numeric type (float/float64/Double), which is inconsistent with the W3C Payment Request API spec where value is defined as a DOMString. This PR aligns the type definition with the W3C standard for cross-language consistency.

Changes

• Change PaymentCurrencyAmount.value from numeric type to string across Python (float → str), Go (float64 → string), and Kotlin (Double → String)
• Update all sample code to use string literal values (e.g., "2.00" instead of 2.00) and add float() / strconv.ParseFloat() conversions where arithmetic operations are needed

Files changed (8 files)

File	Change
src/ap2/types/payment_request.py	float → str
samples/go/pkg/ap2/types/payment_request.go	float64 → string
samples/android/.../data/ShoppingAgentTypes.kt	Double → String
samples/python/.../merchant_agent/tools.py	String literals + float() for sum
samples/python/.../sub_agents/catalog_agent.py	float() conversion for arithmetic
samples/go/.../merchant_agent/tools.go	String literals + strconv conversions
samples/go/.../merchant_agent/storage.go	strconv.FormatFloat for Price→Value
samples/android/.../agent/DpcHelper.kt	Remove redundant .toString() calls

Test plan

• Verify Python samples run correctly with string values
• Verify Go samples compile and run correctly
• Verify Android sample builds successfully

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[gemini-code-assist]

Summary of Changes

Hello, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request addresses an inconsistency between the current implementation and the W3C Payment Request API specification by changing the PaymentCurrencyAmount.value field to a string type. This ensures cross-language consistency and requires updates to sample code to handle arithmetic operations with string values.

Highlights

• Type Change: The PaymentCurrencyAmount.value field was changed from a numeric type (float/float64/Double) to a string type across Python, Go, and Kotlin to align with the W3C Payment Request API spec.
• Code Updates: Sample code was updated to use string literal values for monetary amounts (e.g., "2.00" instead of 2.00).
• Arithmetic Operations: Explicit conversions to numeric types (float() in Python, strconv.ParseFloat() in Go) were added where arithmetic operations are performed on the value field.

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[gemini-code-assist]

Code Review

This pull request correctly aligns the PaymentCurrencyAmount.value type with the W3C specification by changing it from a numeric type to a string across the Python, Go, and Kotlin codebases. The changes are consistent and well-executed. My feedback focuses on improving the robustness of the implementation by adding error handling for string-to-numeric conversions and ensuring consistent formatting for currency values, which is crucial when dealing with monetary data.

[gemini-code-assist]

The error from strconv.ParseFloat is ignored. If an item's amount is not a valid number, it will be silently added as 0 to the total. This could lead to incorrect calculations. It's better to log this error for debugging purposes. For example:

v, err := strconv.ParseFloat(item.Amount.Value, 64)
if err != nil {
    fmt.Fprintf(os.Stderr, "could not parse item value '%s', treating as 0: %v\n", item.Amount.Value, err)
}
newTotal += v

[gemini-code-assist]

The float() conversion could raise a ValueError if item.amount.value is not a valid number string. This would crash the request. It's safer to wrap this in a try...except ValueError block to handle potential malformed data gracefully.

[gemini-code-assist]

This block can be improved for robustness and formatting.

1. Error Handling: The float() conversion will raise a ValueError if a value is not a valid number, which will crash the tool.
2. Currency Formatting: str(sum(...)) doesn't guarantee two decimal places for the currency value (e.g., str(1.5) is '1.5').

Consider refactoring this to handle errors and format the output correctly. You may need to import logging.

total = 0
for item in payment_request.details.display_items:
    try:
        total += float(item.amount.value)
    except (ValueError, TypeError):
        logging.warning(f'Invalid value for item amount, skipping: {item.amount.value}')
payment_request.details.total.amount.value = f'{total:.2f}'