Configuration quoted and unquoted map keys

[radcortez]

When a map key does not contain dots, it can be written in both quoted and unquoted forms:

map.key.url=https://example.com
map.key.timeout=2000

or

map."key".url=https://example.com
map."key".timeout=2000

Both forms are valid and equivalent for simple keys (no dots). However, when both forms are present in the configuration for the same logical key, properties from one form are silently lost:

map."key".url=https://example.com
map.key.timeout=2000

Instead of producing one map entry with both url and timeout populated, only properties from one notation are bound. The other form's values are silently ignored, and which form wins depends on iteration order, hence our recommendation to use the same form: https://smallrye.io/smallrye-config/Latest/config/mappings/#maps.

Root Cause

There is a mismatch between how property names are compared and how map keys are extracted:

• Property name comparison treats map.key.url and map."key".url as two different names — quotes are only significant when the key contains dots.
• Map key extraction strips quotes, so both forms resolve to the same key, to store the unquoted key in the Map

When building a map with a complex value type (a nested object), the code commits to one path form per key and constructs the nested object in a single pass using that path. Properties defined with the other form are never found because the property name comparison considers them different.

In many cases, extensions generate additional configurations that may not follow the user syntax (usually, we don't add quotes to single names, but the user may use them).

Comparison with Spring Boot

Spring Boot uses bracket notation (map[key].url) instead of quotes. For simple keys, both map.key.url and map[key].url are valid. When mixed for a complex object, Spring also binds properties from only one notation — the other is silently ignored. However, Spring's behavior is deterministic (bracket notation takes precedence), while in SmallRye Config the result depends on property name iteration order.

Possible Solutions

Multiple Quarkus extensions have independently worked around this at the extension level:

• Produce both quoted and unquoted variants of schema management config #54492
• Improve compatibility of the REST Client configuration #42932
• Fix dev service always restarting on named datasource configuration change #41736

Ideally, this should be fixed in SmallRye Config directly:

• When building a map, always use the unquoted form as the canonical path for simple keys. This ensures the nested object is always constructed against a consistent, predictable path.
• Fallback lookup: When a property is not found under the canonical (unquoted) name, try the quoted form. This handles the case where a config source only stores the value under the quoted key. Since config sources are provided by external implementations and cannot be modified, the fallback must happen at the lookup layer controlled by SmallRye Config.

Unfortunately, I don't see any other solution than a fallback lookup. I've always refrained from implementing it, because it would potentially cause an explosion of lookups, as explained here: #52690 (comment).

The only other solution I see is to force the use of quotes (or even brackets) on any Map segment, either simple or composed. This actually has the benefit of visually making it clear that a specific segment of a configuration is actually a user-defined name (or dynamic name).

Related

• Inconsistency using quotation marks in named datasources #52690 — Inconsistency using quotation marks in named datasources
• Produce both quoted and unquoted variants of schema management config #54492 — Produce both quoted and unquoted variants of schema management config
• Dev services (new model?) may not apply "additional configuration provider"'s config properly #52699 — Dev services may not apply additional configuration provider's config properly
• Fix dev service always restarting on named datasource configuration change #41736 — Fix dev service always restarting on named datasource configuration change
• Improve compatibility of the REST Client configuration #42932 — Improve compatibility of the REST Client configuration
• Stork environment variable resolution not working properly #41344 — Stork environment variable resolution not working properly
• SRCFG00014 when defining map value from env var #50442 — SRCFG00014 when defining map value from env var
• Problem with environment variables when using multiple datasources #12968 — Problem with environment variables when using multiple datasources
• Cache name with hyphen/dash loses the hyphen during configuration binding in Quarkus Cache Caffeine #54940 — Cache name with hyphen loses the hyphen during configuration binding

[radcortez]

//cc @gsmet