Generate validation rules for map attributes

[bendrucker]

Extends the generator to produce validation rules for map-type attributes (tags, labels, environment variables) using key/value constraints from Smithy models. Adds 124 new tag validation rules across 48 services.

Changes

• Extends generator to support listmap(ListShape, KeyShape, ValueShape) syntax in mapping files
• Shapes in eval context are now rich objects carrying all constraint info
• Transform functions (uppercase, replace) operate on shape enum values
• Adds map_rule.go.tmpl template for map validation rules
• Cleans up dead code and adds safe type assertions

Implementation

AWS services define tags using two different patterns in their Smithy models.

Smithy map Type

Some services use a map type with explicit key and value targets:

TagMap (map)
  ├── key → TagKey (string with constraints)
  └── value → TagValue (string with constraints)

The generator traverses this automatically via traverseToMapConstraints(). No mapping file changes needed—just reference the shape name.

List of Structures

Most services use a list containing a structure with named members:

TagList (list)
  └── member → Tag (structure)
                 ├── Key → TagKey (string with constraints)
                 └── Value → TagValue (string with constraints)

This pattern cannot be inferred automatically because member names vary across services (key/Key/TagKey, value/Value/TagValue). To avoid hardcoding member name lookups, I introduced the listmap() function:

tags = listmap(TagList, TagKey, TagValue)

This explicitly specifies which shapes provide list-level, key, and value constraints. The generator resolves each shape to a rich object containing pattern, length, and enum constraints, then combines them into a single map validation rule.

Shape Objects in Eval Context

The generator now represents each Smithy shape as a cty object:

shapeType = cty.Object({
    "name":    cty.String,
    "type":    cty.String,
    "pattern": cty.String,
    "min":     cty.Number,
    "max":     cty.Number,
    "enum":    cty.List(cty.String),
})

This allows HCL expressions to directly reference shapes by name. Transform functions like uppercase() and replace() operate on the shape's enum values and return a new shape with transformed values:

compression_type = uppercase(CompressionTypeValue)
encryption_mode  = uppercase(replace(EncryptionModeValue, "-", "_"))

Regex Pattern Compatibility

Tag key patterns often include negative lookahead like (?!aws:) to prevent reserved prefixes. Since Go's regexp doesn't support lookahead, these patterns are stripped. The character class validation still applies.

Testing

• Table-driven tests for shape traversal functions
• Tests verify listmap() function combines constraints correctly
• Generator tests confirm transforms operate on shape objects
• Full build and test suite passes

References

• eCloses Validate tags attributes #1019