TS: static is() type guard on profile classes

examples/typescript-r4/extension-profile.test.ts

@@ -74,3 +74,12 @@ test("create() with no required params", () => {
     const profile = nationalityProfile.create();
     expect(profile.toResource().url).toBe("http://hl7.org/fhir/StructureDefinition/patient-nationality");
 });
+
+test("is() matches extensions by url", () => {
+    const ext = birthPlaceProfile.createResource({ valueAddress: { city: "Bonn" } });
+    expect(birthPlaceProfile.is(ext)).toBe(true);
+    expect(birthTimeProfile.is(ext)).toBe(false);
+    expect(birthPlaceProfile.is({ url: "http://example.com/other" })).toBe(false);
+    expect(birthPlaceProfile.is(null)).toBe(false);
+    expect(birthPlaceProfile.is("not an object")).toBe(false);
+});

examples/typescript-r4/fhir-types/hl7-fhir-r4-core/profiles/Extension_birthPlace.ts

@@ -38,6 +38,11 @@ export class birthPlaceProfile {
         return profile;
     }
 
+    static is (resource: unknown) : resource is Extension {
+        if (typeof resource !== "object" || resource === null) return false;
+        return (resource as { url?: string }).url === birthPlaceProfile.canonicalUrl;
+    }
+
     static apply (resource: Extension) : birthPlaceProfile {
         resource.url = birthPlaceProfile.canonicalUrl;
         Object.assign(resource, {

examples/typescript-r4/fhir-types/hl7-fhir-r4-core/profiles/Extension_birthTime.ts

@@ -37,6 +37,11 @@ export class birthTimeProfile {
         return profile;
     }
 
+    static is (resource: unknown) : resource is Extension {
+        if (typeof resource !== "object" || resource === null) return false;
+        return (resource as { url?: string }).url === birthTimeProfile.canonicalUrl;
+    }
+
     static apply (resource: Extension) : birthTimeProfile {
         resource.url = birthTimeProfile.canonicalUrl;
         Object.assign(resource, {

examples/typescript-r4/fhir-types/hl7-fhir-r4-core/profiles/Extension_nationality.ts

@@ -49,6 +49,11 @@ export class nationalityProfile {
         return profile;
     }
 
+    static is (resource: unknown) : resource is Extension {
+        if (typeof resource !== "object" || resource === null) return false;
+        return (resource as { url?: string }).url === nationalityProfile.canonicalUrl;
+    }
+
     static apply (resource: Extension) : nationalityProfile {
         resource.url = nationalityProfile.canonicalUrl;
         Object.assign(resource, {

examples/typescript-r4/fhir-types/hl7-fhir-r4-core/profiles/Extension_own_prefix.ts

@@ -37,6 +37,11 @@ export class own_prefixProfile {
         return profile;
     }
 
+    static is (resource: unknown) : resource is Extension {
+        if (typeof resource !== "object" || resource === null) return false;
+        return (resource as { url?: string }).url === own_prefixProfile.canonicalUrl;
+    }
+
     static apply (resource: Extension) : own_prefixProfile {
         resource.url = own_prefixProfile.canonicalUrl;
         Object.assign(resource, {

examples/typescript-r4/fhir-types/hl7-fhir-r4-core/profiles/Observation_observation_bodyweight.ts

@@ -61,6 +61,13 @@ export class observation_bodyweightProfile {
         return profile;
     }
 
+    static is (resource: unknown) : resource is Observation {
+        if (typeof resource !== "object" || resource === null) return false;
+        const r = resource as { resourceType?: string; meta?: { profile?: string[] } };
+        if (r.resourceType !== "Observation") return false;
+        return (r.meta?.profile ?? []).includes(observation_bodyweightProfile.canonicalUrl);
+    }
+
     static apply (resource: Observation) : observation_bodyweightProfile {
         ensureProfile(resource, observation_bodyweightProfile.canonicalUrl);
         Object.assign(resource, {

examples/typescript-r4/fhir-types/hl7-fhir-r4-core/profiles/Observation_observation_bp.ts

@@ -76,6 +76,13 @@ export class observation_bpProfile {
         return profile;
     }
 
+    static is (resource: unknown) : resource is Observation {
+        if (typeof resource !== "object" || resource === null) return false;
+        const r = resource as { resourceType?: string; meta?: { profile?: string[] } };
+        if (r.resourceType !== "Observation") return false;
+        return (r.meta?.profile ?? []).includes(observation_bpProfile.canonicalUrl);
+    }
+
     static apply (resource: Observation) : observation_bpProfile {
         ensureProfile(resource, observation_bpProfile.canonicalUrl);
         Object.assign(resource, {

examples/typescript-r4/fhir-types/hl7-fhir-r4-core/profiles/Observation_observation_vitalsigns.ts

@@ -61,6 +61,13 @@ export class observation_vitalsignsProfile {
         return profile;
     }
 
+    static is (resource: unknown) : resource is Observation {
+        if (typeof resource !== "object" || resource === null) return false;
+        const r = resource as { resourceType?: string; meta?: { profile?: string[] } };
+        if (r.resourceType !== "Observation") return false;
+        return (r.meta?.profile ?? []).includes(observation_vitalsignsProfile.canonicalUrl);
+    }
+
     static apply (resource: Observation) : observation_vitalsignsProfile {
         ensureProfile(resource, observation_vitalsignsProfile.canonicalUrl);
         resource.category = ensureSliceDefaults(

examples/typescript-r4/profile-bodyweight.test.ts

@@ -108,6 +108,73 @@ describe("demo: read a bodyweight observation from JSON", () => {
     });
 });
 
+describe("demo: filter a mixed collection with is()", () => {
+    test("is() narrows unknown values to profile matches", () => {
+        // A mixed bag: a matching bodyweight, a non-matching Observation, a non-Observation, and junk
+        const bodyweight: Observation = {
+            resourceType: "Observation",
+            meta: { profile: ["http://hl7.org/fhir/StructureDefinition/bodyweight"] },
+            status: "final",
+            code: { coding: [{ code: "29463-7", system: "http://loinc.org" }] },
+            subject: { reference: "Patient/pt-1" },
+            effectiveDateTime: "2024-06-15",
+            valueQuantity: { value: 75, unit: "kg" },
+        };
+        const otherObs: Observation = {
+            resourceType: "Observation",
+            status: "final",
+            code: { coding: [{ code: "8867-4", system: "http://loinc.org" }] },
+        };
+        const resources: unknown[] = [bodyweight, otherObs, { resourceType: "Patient" }, null, "not a resource"];
+
+        // is() is a cheap type guard — no validation, no instance constructed
+        const matches = resources.filter(bodyweightProfile.is);
+
+        expect(matches).toEqual([bodyweight]);
+    });
+});
+
+describe("is() type guard", () => {
+    test("returns true for Observation with matching meta.profile", () => {
+        const obs: Observation = {
+            resourceType: "Observation",
+            meta: { profile: ["http://hl7.org/fhir/StructureDefinition/bodyweight"] },
+            status: "final",
+            code: { coding: [{ code: "29463-7", system: "http://loinc.org" }] },
+        };
+        expect(bodyweightProfile.is(obs)).toBe(true);
+    });
+
+    test("returns false when meta.profile does not include canonical url", () => {
+        const obs: Observation = {
+            resourceType: "Observation",
+            status: "final",
+            code: { coding: [{ code: "29463-7", system: "http://loinc.org" }] },
+        };
+        expect(bodyweightProfile.is(obs)).toBe(false);
+    });
+
+    test("returns false for wrong resourceType", () => {
+        expect(bodyweightProfile.is({ resourceType: "Patient" })).toBe(false);
+    });
+
+    test("returns false for non-object inputs", () => {
+        expect(bodyweightProfile.is(null)).toBe(false);
+        expect(bodyweightProfile.is(undefined)).toBe(false);
+        expect(bodyweightProfile.is("string")).toBe(false);
+        expect(bodyweightProfile.is(42)).toBe(false);
+    });
+
+    test("does not validate — only checks identity", () => {
+        // A resource that claims the profile but is otherwise invalid still passes is()
+        const bogus = {
+            resourceType: "Observation",
+            meta: { profile: ["http://hl7.org/fhir/StructureDefinition/bodyweight"] },
+        };
+        expect(bodyweightProfile.is(bogus)).toBe(true);
+    });
+});
+
 describe("factory method equivalence", () => {
     test("create(), createResource(), and apply() produce equal resources", () => {
         const args = { status: "final" as const, subject: { reference: "Patient/pt-1" as const } };

src/api/writer-generator/typescript/profile.ts

@@ -391,6 +391,20 @@ const generateFactoryMethods = (
         w.lineSM("return profile");
     });
     w.line();
+    const canEmitIs = (hasMeta && isResourceIdentifier(flatProfile.base)) || flatProfile.base.name === "Extension";
+    if (canEmitIs) {
+        w.curlyBlock(["static", "is", "(resource: unknown)", `: resource is ${tsBaseResourceName}`], () => {
+            w.line(`if (typeof resource !== "object" || resource === null) return false;`);
+            if (hasMeta && isResourceIdentifier(flatProfile.base)) {
+                w.line(`const r = resource as { resourceType?: string; meta?: { profile?: string[] } };`);
+                w.line(`if (r.resourceType !== ${JSON.stringify(flatProfile.base.name)}) return false;`);
+                w.lineSM(`return (r.meta?.profile ?? []).includes(${profileClassName}.canonicalUrl)`);
+            } else {
+                w.lineSM(`return (resource as { url?: string }).url === ${profileClassName}.canonicalUrl`);
+            }
+        });
+        w.line();
+    }
     w.curlyBlock(["static", "apply", `(resource: ${tsBaseResourceName})`, `: ${profileClassName}`], () => {
         if (hasMeta) {
             w.lineSM(`ensureProfile(resource, ${profileClassName}.canonicalUrl)`);

test/api/write-generator/__snapshots__/typescript.test.ts.snap

@@ -375,6 +375,13 @@ export class observation_bodyweightProfile {
         return profile;
     }
 
+    static is (resource: unknown) : resource is Observation {
+        if (typeof resource !== "object" || resource === null) return false;
+        const r = resource as { resourceType?: string; meta?: { profile?: string[] } };
+        if (r.resourceType !== "Observation") return false;
+        return (r.meta?.profile ?? []).includes(observation_bodyweightProfile.canonicalUrl);
+    }
+
     static apply (resource: Observation) : observation_bodyweightProfile {
         ensureProfile(resource, observation_bodyweightProfile.canonicalUrl);
         Object.assign(resource, {
@@ -607,6 +614,13 @@ export class observation_bpProfile {
         return profile;
     }
 
+    static is (resource: unknown) : resource is Observation {
+        if (typeof resource !== "object" || resource === null) return false;
+        const r = resource as { resourceType?: string; meta?: { profile?: string[] } };
+        if (r.resourceType !== "Observation") return false;
+        return (r.meta?.profile ?? []).includes(observation_bpProfile.canonicalUrl);
+    }
+
     static apply (resource: Observation) : observation_bpProfile {
         ensureProfile(resource, observation_bpProfile.canonicalUrl);
         Object.assign(resource, {
@@ -897,6 +911,13 @@ export class USCorePatientProfile {
         return profile;
     }
 
+    static is (resource: unknown) : resource is Patient {
+        if (typeof resource !== "object" || resource === null) return false;
+        const r = resource as { resourceType?: string; meta?: { profile?: string[] } };
+        if (r.resourceType !== "Patient") return false;
+        return (r.meta?.profile ?? []).includes(USCorePatientProfile.canonicalUrl);
+    }
+
     static apply (resource: Patient) : USCorePatientProfile {
         ensureProfile(resource, USCorePatientProfile.canonicalUrl);
         return new USCorePatientProfile(resource);
@@ -1168,6 +1189,13 @@ export class USCoreBloodPressureProfile {
         return profile;
     }
 
+    static is (resource: unknown) : resource is Observation {
+        if (typeof resource !== "object" || resource === null) return false;
+        const r = resource as { resourceType?: string; meta?: { profile?: string[] } };
+        if (r.resourceType !== "Observation") return false;
+        return (r.meta?.profile ?? []).includes(USCoreBloodPressureProfile.canonicalUrl);
+    }
+
     static apply (resource: Observation) : USCoreBloodPressureProfile {
         ensureProfile(resource, USCoreBloodPressureProfile.canonicalUrl);
         Object.assign(resource, {
@@ -1550,6 +1578,13 @@ export class USCoreBodyWeightProfile {
         return profile;
     }
 
+    static is (resource: unknown) : resource is Observation {
+        if (typeof resource !== "object" || resource === null) return false;
+        const r = resource as { resourceType?: string; meta?: { profile?: string[] } };
+        if (r.resourceType !== "Observation") return false;
+        return (r.meta?.profile ?? []).includes(USCoreBodyWeightProfile.canonicalUrl);
+    }
+
     static apply (resource: Observation) : USCoreBodyWeightProfile {
         ensureProfile(resource, USCoreBodyWeightProfile.canonicalUrl);
         Object.assign(resource, {
@@ -1881,6 +1916,11 @@ export class USCoreRaceExtensionProfile {
         return profile;
     }
 
+    static is (resource: unknown) : resource is Extension {
+        if (typeof resource !== "object" || resource === null) return false;
+        return (resource as { url?: string }).url === USCoreRaceExtensionProfile.canonicalUrl;
+    }
+
     static apply (resource: Extension) : USCoreRaceExtensionProfile {
         resource.url = USCoreRaceExtensionProfile.canonicalUrl;
         Object.assign(resource, {

test/api/write-generator/multi-package/__snapshots__/local-package.test.ts.snap

@@ -92,6 +92,13 @@ export class ExampleTypedBundleProfile {
         return profile;
     }
 
+    static is (resource: unknown) : resource is Bundle {
+        if (typeof resource !== "object" || resource === null) return false;
+        const r = resource as { resourceType?: string; meta?: { profile?: string[] } };
+        if (r.resourceType !== "Bundle") return false;
+        return (r.meta?.profile ?? []).includes(ExampleTypedBundleProfile.canonicalUrl);
+    }
+
     static apply (resource: Bundle) : ExampleTypedBundleProfile {
         ensureProfile(resource, ExampleTypedBundleProfile.canonicalUrl);
         return new ExampleTypedBundleProfile(resource);