@amritk/generate-examples - npm Package Compare versions

Comparing version 0.3.2 to 0.4.0

dist/generators/derive-example.js

 import { getMjstInstanceOf, getMjstPrimitive } from '@amritk/helpers/mjst-extension';
 import { resolveRef } from '@amritk/helpers/resolve-ref';
-import { hasAnyOf, hasConst, hasDefault, hasEnum, hasExamples, hasFormat, hasItems, hasMaxLength, hasMinItems, hasMinimum, hasMinLength, hasOneOf, hasProperties, hasRef, hasType, isSchemaObject, } from '@amritk/helpers/schema-guards';
+import { hasAdditionalProperties, hasAllOf, hasAnyOf, hasConst, hasDefault, hasEnum, hasExamples, hasExclusiveMaximum, hasExclusiveMinimum, hasFormat, hasItems, hasMaxItems, hasMaximum, hasMaxLength, hasMinItems, hasMinimum, hasMinLength, hasMinProperties, hasMultipleOf, hasOneOf, hasPattern, hasProperties, hasRef, hasRequired, hasType, hasUniqueItems, isSchemaObject, } from '@amritk/helpers/schema-guards';
 /** Lowercases the first character of a name. e.g. "User" → "user" */
@@ -8,3 +8,165 @@ const lowerFirst = (name) => name.charAt(0).toLowerCase() + name.slice(1);
 const exampleName = (typeName) => `${lowerFirst(typeName)}Example`;
-/** Returns a representative string honouring `format` and length constraints. */
+/** A representative character for a single regex atom (class body / escape). */
+const charForClass = (inner) => {
+    if (/a-z/.test(inner))
+        return 'a';
+    if (/A-Z/.test(inner))
+        return 'A';
+    if (/0-9|\\d/.test(inner))
+        return '5';
+    const first = inner.replace(/^\^/, '')[0];
+    return first && first !== '\\' ? first : 'a';
+};
+const charForEscape = (esc) => {
+    if (esc === '\\d')
+        return '5';
+    if (esc === '\\w')
+        return 'a';
+    if (esc === '\\s')
+        return ' ';
+    return esc[1] ?? 'a';
+};
+/** Splits `s` on top-level `|`, respecting `[...]` and `(...)` nesting. */
+const topLevelAlternatives = (s) => {
+    const parts = [];
+    let depth = 0;
+    let inClass = false;
+    let cur = '';
+    for (let i = 0; i < s.length; i++) {
+        const c = s[i];
+        if (c === '\\') {
+            cur += c + (s[i + 1] ?? '');
+            i++;
+            continue;
+        }
+        if (inClass) {
+            cur += c;
+            if (c === ']')
+                inClass = false;
+            continue;
+        }
+        if (c === '[')
+            inClass = true;
+        else if (c === '(')
+            depth++;
+        else if (c === ')')
+            depth--;
+        else if (c === '|' && depth === 0) {
+            parts.push(cur);
+            cur = '';
+            continue;
+        }
+        cur += c;
+    }
+    parts.push(cur);
+    return parts;
+};
+/**
+ * Best-effort generator of a string matching a `pattern`, via recursive descent:
+ * anchors, literals, `.`, escapes (`\d`/`\w`/`\s`), character classes, groups
+ * (capturing / non-capturing / named), alternation (`a|b` — picks the first
+ * usable branch), and the `+`/`*`/`?`/`{n}`/`{n,m}` quantifiers. Lookarounds and
+ * backreferences fall through to `undefined`. The caller verifies the result
+ * against the real regex and only uses it on a match, so a partial sampler never
+ * makes the example worse — it just upgrades the cases it understands.
+ */
+const sampleFromPattern = (pattern, minLength) => {
+    let body = pattern;
+    if (body.startsWith('^'))
+        body = body.slice(1);
+    if (body.endsWith('$') && !body.endsWith('\\$'))
+        body = body.slice(0, -1);
+    // Samples one alternation, preferring the first branch that samples cleanly.
+    const sampleAlt = (s) => {
+        for (const alt of topLevelAlternatives(s)) {
+            const r = sampleSeq(alt);
+            if (r !== undefined)
+                return r;
+        }
+        return undefined;
+    };
+    // Samples one concatenation (no top-level `|`).
+    const sampleSeq = (seq) => {
+        let out = '';
+        let i = 0;
+        while (i < seq.length) {
+            let unit;
+            const c = seq[i];
+            if (c === '(') {
+                // Find the matching close paren.
+                let depth = 1;
+                let j = i + 1;
+                for (; j < seq.length && depth > 0; j++) {
+                    const cj = seq[j];
+                    if (cj === '\\') {
+                        j++;
+                        continue;
+                    }
+                    if (cj === '(')
+                        depth++;
+                    else if (cj === ')')
+                        depth--;
+                }
+                if (depth !== 0)
+                    return undefined;
+                let inner = seq.slice(i + 1, j - 1);
+                if (/^\?[=!]/.test(inner) || /^\?<[=!]/.test(inner))
+                    return undefined; // lookaround
+                inner = inner.replace(/^\?:/, '').replace(/^\?<[^>]*>/, '');
+                unit = sampleAlt(inner);
+                if (unit === undefined)
+                    return undefined;
+                i = j;
+            }
+            else if (c === '[') {
+                const end = seq.indexOf(']', i + 1);
+                if (end === -1)
+                    return undefined;
+                unit = charForClass(seq.slice(i + 1, end));
+                i = end + 1;
+            }
+            else if (c === '\\') {
+                const esc = seq.slice(i, i + 2);
+                if (/\d/.test(esc[1] ?? ''))
+                    return undefined; // backreference
+                unit = charForEscape(esc);
+                i += 2;
+            }
+            else if (c === '.') {
+                unit = 'a';
+                i++;
+            }
+            else {
+                unit = c;
+                i++;
+            }
+            // Optional quantifier.
+            let reps = 1;
+            const q = seq[i];
+            if (q === '+') {
+                reps = Math.max(1, minLength);
+                i++;
+            }
+            else if (q === '*') {
+                reps = Math.max(0, minLength);
+                i++;
+            }
+            else if (q === '?') {
+                reps = 1;
+                i++;
+            }
+            else if (q === '{') {
+                const end = seq.indexOf('}', i + 1);
+                if (end === -1)
+                    return undefined;
+                reps = Number.parseInt(seq.slice(i + 1, end), 10) || 0;
+                i = end + 1;
+            }
+            out += unit.repeat(reps);
+        }
+        return out;
+    };
+    return sampleAlt(body);
+};
+/** Returns a representative string honouring `format`, `pattern`, and length. */
 const exampleString = (schema) => {
@@ -34,5 +196,14 @@ if (hasFormat(schema)) {
     }
+    const minLength = hasMinLength(schema) ? schema.minLength : 0;
+    if (hasPattern(schema)) {
+        const sampled = sampleFromPattern(schema.pattern, minLength);
+        // Only trust the sampler when it actually matches and fits the length bound.
+        if (sampled !== undefined && new RegExp(schema.pattern).test(sampled)) {
+            if (!(hasMaxLength(schema) && sampled.length > schema.maxLength))
+                return sampled;
+        }
+    }
     let value = 'string';
-    if (hasMinLength(schema) && value.length < schema.minLength)
-        value = value.padEnd(schema.minLength, 'x');
+    if (value.length < minLength)
+        value = value.padEnd(minLength, 'x');
     if (hasMaxLength(schema) && value.length > schema.maxLength)
@@ -62,4 +233,8 @@ value = value.slice(0, schema.maxLength);
         return schema.default;
-    if (hasEnum(schema) && schema.enum.length > 0)
-        return schema.enum[0];
+    if (hasEnum(schema) && schema.enum.length > 0) {
+        // Prefer the first member that also satisfies any sibling length/range
+        // constraints (e.g. `enum` + `minLength`), falling back to the first member.
+        const fitting = schema.enum.find((value) => satisfiesScalarConstraints(schema, value));
+        return fitting !== undefined ? fitting : schema.enum[0];
+    }
     if (hasRef(schema)) {
@@ -80,2 +255,7 @@ const ref = schema.$ref;
         return 0n;
+    // `allOf` must satisfy every branch at once, so derive from a single schema
+    // that merges the branches (and the node's own keywords) rather than picking
+    // one branch — picking one would ignore the others' constraints.
+    if (hasAllOf(schema))
+        return deriveExample(mergeAllOf(schema), rootSchema, seen);
     if (hasOneOf(schema) && schema.oneOf[0] !== undefined)
@@ -94,2 +274,28 @@ return deriveExample(schema.oneOf[0], rootSchema, seen);
 };
+/**
+ * True when a candidate value (e.g. an `enum`/`const` member) satisfies the
+ * node's simple string-length and numeric-range constraints. Used to pick an
+ * `enum` member that also meets a sibling `minLength`/`minimum`/etc.
+ */
+const satisfiesScalarConstraints = (schema, value) => {
+    if (typeof value === 'string') {
+        if (hasMinLength(schema) && value.length < schema.minLength)
+            return false;
+        if (hasMaxLength(schema) && value.length > schema.maxLength)
+            return false;
+    }
+    else if (typeof value === 'number') {
+        if (hasMinimum(schema) && value < schema.minimum)
+            return false;
+        if (hasMaximum(schema) && value > schema.maximum)
+            return false;
+        if (hasExclusiveMinimum(schema) && value <= schema.exclusiveMinimum)
+            return false;
+        if (hasExclusiveMaximum(schema) && value >= schema.exclusiveMaximum)
+            return false;
+        if (hasMultipleOf(schema) && schema.multipleOf > 0 && value % schema.multipleOf !== 0)
+            return false;
+    }
+    return true;
+};
 /** Derives a canonical value for a single declared `type`. */
@@ -102,3 +308,3 @@ const deriveForType = (type, schema, rootSchema, seen) => {
         case 'integer':
-            return hasMinimum(schema) ? schema.minimum : 0;
+            return deriveNumber(schema, type === 'integer');
         case 'boolean':
@@ -108,7 +314,4 @@ return true;
             return null;
-        case 'array': {
-            const item = hasItems(schema) ? deriveExample(schema.items, rootSchema, seen) : null;
-            const count = hasMinItems(schema) ? Math.max(schema.minItems, 1) : 1;
-            return Array.from({ length: count }, () => item);
-        }
+        case 'array':
+            return deriveArray(schema, rootSchema, seen);
         case 'object': {
@@ -121,2 +324,25 @@ const out = {};
             }
+            const additional = hasAdditionalProperties(schema) ? schema.additionalProperties : false;
+            const additionalSchema = isSchemaObject(additional) ? additional : undefined;
+            // Extra keys are allowed unless `additionalProperties: false` forbids them.
+            const extrasAllowed = !(hasAdditionalProperties(schema) && schema.additionalProperties === false);
+            // A required key with no `properties` entry still needs a value. Use the
+            // `additionalProperties` schema when one constrains it, else a null.
+            if (hasRequired(schema)) {
+                for (const key of schema.required) {
+                    if (key in out)
+                        continue;
+                    out[key] = additionalSchema ? deriveExample(additionalSchema, rootSchema, seen) : null;
+                }
+            }
+            // Synthesize filler keys to reach `minProperties` when extras are allowed.
+            if (hasMinProperties(schema) && extrasAllowed) {
+                let n = 0;
+                while (Object.keys(out).length < schema.minProperties) {
+                    const key = `extra${n++}`;
+                    if (key in out)
+                        continue;
+                    out[key] = additionalSchema ? deriveExample(additionalSchema, rootSchema, seen) : null;
+                }
+            }
             return out;
@@ -129,2 +355,185 @@ }
 /**
+ * Picks a number satisfying the node's bounds and `multipleOf`. Starts at the
+ * lower bound (or 0 when unbounded), nudges past an exclusive bound, then rounds
+ * up to the nearest multiple. An unsatisfiable range (e.g. `minimum > maximum`)
+ * can't be met and falls back to the lower bound.
+ */
+const deriveNumber = (schema, isInteger) => {
+    const step = isInteger ? 1 : 0.5;
+    let lo = -Infinity;
+    if (hasMinimum(schema))
+        lo = Math.max(lo, schema.minimum);
+    if (hasExclusiveMinimum(schema))
+        lo = Math.max(lo, schema.exclusiveMinimum + step);
+    const hi = hasMaximum(schema)
+        ? schema.maximum
+        : hasExclusiveMaximum(schema)
+            ? schema.exclusiveMaximum - step
+            : Number.POSITIVE_INFINITY;
+    // Base candidate: the lower bound, or 0 (or the upper bound) when unbounded below.
+    let value = Number.isFinite(lo) ? lo : Number.isFinite(hi) ? Math.min(0, hi) : 0;
+    if (isInteger)
+        value = Math.ceil(value);
+    if (hasMultipleOf(schema) && schema.multipleOf > 0) {
+        const m = schema.multipleOf;
+        value = Math.ceil(value / m - 1e-9) * m;
+        // Rounding up can overshoot the upper bound; drop to the largest multiple
+        // that fits. (If even that falls below `lo`, the range has no multiple — an
+        // unsatisfiable schema — and we return the in-range candidate as best effort.)
+        if (value > hi && Number.isFinite(hi))
+            value = Math.floor(hi / m + 1e-9) * m;
+    }
+    // `+ 0` normalizes a `-0` (which `Math.ceil`/`Math.floor` can produce) to `0`.
+    return (isInteger ? Math.round(value) : value) + 0;
+};
+/**
+ * Derives an array value. A tuple schema (`prefixItems`, or the draft-07
+ * array-form `items`) derives one value per position; a uniform array repeats a
+ * single item value. The count is clamped into `[minItems, maxItems]` so a
+ * `maxItems: 0` yields `[]` and a `minItems` is always met.
+ */
+const deriveArray = (schema, rootSchema, seen) => {
+    const items = hasItems(schema) ? schema.items : undefined;
+    const prefixItems = schema['prefixItems'];
+    // A tuple is `prefixItems` (2020-12) or the draft-07 array-form `items`.
+    const prefix = Array.isArray(prefixItems)
+        ? prefixItems
+        : Array.isArray(items)
+            ? items
+            : undefined;
+    const min = hasMinItems(schema) ? schema.minItems : 0;
+    const max = hasMaxItems(schema) ? schema.maxItems : Number.POSITIVE_INFINITY;
+    // The rest/uniform element schema (the singular object-form `items`). A boolean
+    // `items` (`true`/`false`) is not a value-producing schema, so it is not `rest`.
+    const rest = items !== undefined && !Array.isArray(items) && isSchemaObject(items) ? items : undefined;
+    if (prefix) {
+        const tuple = prefix.map((item) => deriveExample(item, rootSchema, seen));
+        // Pad up to `minItems`: with the rest schema when one is present, otherwise
+        // (in 2020-12 additional items past `prefixItems` are unconstrained unless
+        // `items: false`) with a plain `null`.
+        const itemsClosed = schema['items'] === false;
+        while (tuple.length < min && tuple.length < max) {
+            if (rest !== undefined)
+                tuple.push(deriveExample(rest, rootSchema, seen));
+            else if (itemsClosed)
+                break;
+            else
+                tuple.push(null);
+        }
+        return tuple.length > max ? tuple.slice(0, max) : tuple;
+    }
+    const raw = schema;
+    const containsRaw = raw['contains'];
+    const contains = containsRaw !== undefined && isSchemaObject(containsRaw) ? containsRaw : undefined;
+    const minContains = contains !== undefined ? (typeof raw['minContains'] === 'number' ? raw['minContains'] : 1) : 0;
+    const unique = hasUniqueItems(schema) && schema.uniqueItems === true;
+    // The element schema: the uniform `items`, else the `contains` subschema.
+    const elem = rest ?? contains;
+    // Prefer a non-empty example, satisfy `minItems` and `minContains`, never exceed `maxItems`.
+    const count = Math.min(Math.max(min, minContains, max === 0 ? 0 : 1), max);
+    const result = [];
+    for (let i = 0; i < count; i++) {
+        // Make the first `minContains` items satisfy `contains`; the rest use `items`.
+        const itemSchema = contains !== undefined && i < minContains ? contains : elem;
+        const base = itemSchema !== undefined ? deriveExample(itemSchema, rootSchema, seen) : null;
+        result.push(unique ? distinctify(base, i, itemSchema) : base);
+    }
+    return result;
+};
+/**
+ * Returns a value distinct from earlier ones for index `i`, used to satisfy
+ * `uniqueItems`, while staying within the item schema's constraints: numbers step
+ * by `multipleOf` (so the perturbed values remain valid multiples) rather than by
+ * 1, strings are suffixed, booleans alternated. Values that can't be cheaply
+ * varied are returned as-is (a best-effort the generated `fast-check` arbitrary
+ * covers fully).
+ */
+const distinctify = (base, i, itemSchema) => {
+    if (i === 0)
+        return base;
+    if (typeof base === 'number') {
+        const step = itemSchema && isSchemaObject(itemSchema) && hasMultipleOf(itemSchema) && itemSchema.multipleOf > 0
+            ? itemSchema.multipleOf
+            : 1;
+        return base + i * step;
+    }
+    if (typeof base === 'string')
+        return `${base}${i}`;
+    if (typeof base === 'boolean')
+        return i % 2 === 1 ? !base : base;
+    return base;
+};
+/**
+ * Flattens an `allOf` into a single schema: object `properties` are merged and
+ * `required` unioned across branches, while scalar keywords from later branches
+ * (and the node's own keywords) win. `allOf` itself is dropped so the merged
+ * schema derives directly.
+ */
+const TIGHTEST = new Map([
+    ['minimum', 'max'],
+    ['exclusiveMinimum', 'max'],
+    ['minLength', 'max'],
+    ['minItems', 'max'],
+    ['minProperties', 'max'],
+    ['maximum', 'min'],
+    ['exclusiveMaximum', 'min'],
+    ['maxLength', 'min'],
+    ['maxItems', 'min'],
+    ['maxProperties', 'min'],
+]);
+const mergeAllOf = (schema) => {
+    const branches = hasAllOf(schema) ? schema.allOf : [];
+    const merged = {};
+    const properties = {};
+    const required = new Set();
+    for (const branch of [...branches, schema]) {
+        if (!isSchemaObject(branch))
+            continue;
+        for (const [key, value] of Object.entries(branch)) {
+            if (key === 'allOf')
+                continue;
+            if (key === 'properties' && value && typeof value === 'object') {
+                // The same property constrained by several branches must satisfy all of
+                // them, so collect each schema and combine them below rather than letting
+                // a later branch's schema silently replace an earlier one.
+                for (const [prop, propSchema] of Object.entries(value)) {
+                    const bucket = properties[prop];
+                    if (bucket)
+                        bucket.push(propSchema);
+                    else
+                        properties[prop] = [propSchema];
+                }
+            }
+            else if (key === 'required' && Array.isArray(value)) {
+                for (const r of value)
+                    required.add(r);
+            }
+            else if (key === 'enum' && Array.isArray(value)) {
+                // A value must be in *every* branch's enum, so intersect rather than let
+                // a later branch's enum replace an earlier one (which could pick a member
+                // the earlier branch rejects).
+                merged['enum'] = Array.isArray(merged['enum'])
+                    ? merged['enum'].filter((member) => value.includes(member))
+                    : value;
+            }
+            else if (TIGHTEST.has(key) && typeof value === 'number' && typeof merged[key] === 'number') {
+                // Numeric bounds from different branches combine to the tightest one.
+                merged[key] = TIGHTEST.get(key) === 'max' ? Math.max(merged[key], value) : Math.min(merged[key], value);
+            }
+            else {
+                merged[key] = value;
+            }
+        }
+    }
+    const mergedProps = {};
+    for (const [prop, schemas] of Object.entries(properties)) {
+        mergedProps[prop] = schemas.length === 1 ? schemas[0] : { allOf: schemas };
+    }
+    if (Object.keys(mergedProps).length > 0)
+        merged['properties'] = mergedProps;
+    if (required.size > 0)
+        merged['required'] = [...required];
+    return merged;
+};
+/**
  * Serializes a derived value into a TypeScript source expression. Handles the
@@ -131,0 +540,0 @@ * non-JSON values `deriveExample` can produce (`Date`, `bigint`) in addition to

package.json

 {
   "name": "@amritk/generate-examples",
-  "version": "0.3.2",
+  "version": "0.4.0",
   "description": "Generate fast-check arbitraries and example values from JSON Schemas.",
@@ -52,2 +52,5 @@ "module": "./dist/index.js",
   },
+  "devDependencies": {
+    "ajv": "^8.17.1"
+  },
   "peerDependencies": {
@@ -54,0 +57,0 @@ "fast-check": ">=3"

No alert changes

Improved metrics

Total package byte prevSize

51105

51.09%

Lines of code

1069

62.22%

Worsened metrics

Dev dependency count

1

Infinity%

No dependency changes