fix: preserve init accessor on init-only properties

[vbreuss]

This pull request adds support for C# init-only properties in the source generator, ensuring that properties declared with the init accessor are correctly recognized and emitted in generated code. The changes update both the code generation logic and the method/property metadata, and include a new test to verify this functionality.

Support for init-only properties:

• Added an IsInitOnly property to the Method entity to track whether a method or property accessor is init-only.
• Updated property code generation to emit init instead of set for init-only setters in generated mock classes.
• Modified the logic for generating property setters to skip certain code paths for init-only properties, ensuring correct behavior.

[github-actions]

🚀 Benchmark Results

Details

BenchmarkDotNet v0.15.8, Linux Ubuntu 24.04.4 LTS (Noble Numbat)

AMD EPYC 9V74 2.60GHz, 1 CPU, 4 logical and 2 physical cores

.NET SDK 10.0.203

[Host] : .NET 10.0.7 (10.0.7, 10.0.726.21808), X64 RyuJIT x86-64-v3
Job=InProcess  Toolchain=InProcessEmitToolchain  IterationCount=15

LaunchCount=1  WarmupCount=10

Method	Mean	Error	StdDev	Ratio	RatioSD	Gen0	Gen1	Allocated	Alloc Ratio
Event_Mockolate	361.9 ns	6.82 ns	6.38 ns	1.00	0.02	0.1254	0.0005	2.05 KB	1.00
Event_Moq	13,778.9 ns	176.72 ns	156.66 ns	38.09	0.77	0.7324	-	12.51 KB	6.09
Event_NSubstitute	5,598.8 ns	74.99 ns	70.15 ns	15.48	0.32	0.5493	0.0076	9.05 KB	4.40
Event_FakeItEasy	229,565.8 ns	515.36 ns	482.07 ns	634.57	10.92	0.7324	0.4883	15.39 KB	7.49
Event_Imposter	1,490.0 ns	45.31 ns	42.38 ns	4.12	0.13	0.5379	0.0153	8.8 KB	4.29
Event_TUnitMocks	186.8 ns	4.92 ns	4.60 ns	0.52	0.02	0.0837	0.0002	1.37 KB	0.67

Details

BenchmarkDotNet v0.15.8, Linux Ubuntu 24.04.4 LTS (Noble Numbat)

Intel Xeon Platinum 8370C CPU 2.80GHz (Max: 2.77GHz), 1 CPU, 4 logical and 2 physical cores

.NET SDK 10.0.203

[Host] : .NET 10.0.7 (10.0.7, 10.0.726.21808), X64 RyuJIT x86-64-v4
Job=InProcess  Toolchain=InProcessEmitToolchain  IterationCount=15

LaunchCount=1  WarmupCount=10

Method	N	Mean	Error	StdDev	Ratio	RatioSD	Gen0	Gen1	Allocated	Alloc Ratio
Indexer_Mockolate	1	1.036 μs	0.0221 μs	0.0207 μs	1.00	0.03	0.1640	-	4.03 KB	1.00
Indexer_Moq	1	162.116 μs	0.9731 μs	0.9103 μs	156.59	3.12	0.4883	-	20.36 KB	5.05
Indexer_NSubstitute	1	9.040 μs	0.0649 μs	0.0607 μs	8.73	0.18	0.5188	-	12.78 KB	3.17
Indexer_FakeItEasy	1	11.295 μs	0.0616 μs	0.0576 μs	10.91	0.22	0.5646	0.0153	13.87 KB	3.44
Indexer_Imposter	1	1.002 μs	0.0229 μs	0.0214 μs	0.97	0.03	0.2098	0.0019	5.16 KB	1.28
Indexer_Mockolate	10	2.898 μs	0.0175 μs	0.0164 μs	1.00	0.01	0.2060	-	5.09 KB	1.00
Indexer_Moq	10	171.928 μs	0.8577 μs	0.7603 μs	59.34	0.41	0.9766	0.7324	29.89 KB	5.88
Indexer_NSubstitute	10	21.352 μs	0.1276 μs	0.1131 μs	7.37	0.06	1.0376	0.0305	25.58 KB	5.03
Indexer_FakeItEasy	10	23.009 μs	0.0877 μs	0.0777 μs	7.94	0.05	1.4343	0.0610	35.48 KB	6.98
Indexer_Imposter	10	2.189 μs	0.0315 μs	0.0280 μs	0.76	0.01	0.3242	-	7.97 KB	1.57

Details

BenchmarkDotNet v0.15.8, Linux Ubuntu 24.04.4 LTS (Noble Numbat)

AMD EPYC 7763 2.45GHz, 1 CPU, 4 logical and 2 physical cores

.NET SDK 10.0.203

[Host] : .NET 10.0.7 (10.0.7, 10.0.726.21808), X64 RyuJIT x86-64-v3
Job=InProcess  Toolchain=InProcessEmitToolchain  IterationCount=15

LaunchCount=1  WarmupCount=10

Method	N	Mean	Error	StdDev	Ratio	RatioSD	Gen0	Gen1	Allocated	Alloc Ratio
Method_Mockolate	1	445.9 ns	2.98 ns	2.49 ns	1.00	0.01	0.1416	0.0010	2.32 KB	1.00
Method_Moq	1	183,153.5 ns	314.15 ns	262.33 ns	410.72	2.29	0.4883	-	14.58 KB	6.28
Method_NSubstitute	1	5,518.4 ns	19.44 ns	17.23 ns	12.37	0.08	0.5569	0.0076	9.12 KB	3.93
Method_FakeItEasy	1	6,038.2 ns	16.96 ns	15.03 ns	13.54	0.08	0.4959	-	8.11 KB	3.50
Method_Imposter	1	634.6 ns	5.00 ns	4.43 ns	1.42	0.01	0.2470	0.0029	4.04 KB	1.74
Method_TUnitMocks	1	651.4 ns	5.01 ns	4.18 ns	1.46	0.01	0.1774	0.0010	2.9 KB	1.25
Method_Mockolate	10	743.0 ns	5.32 ns	4.98 ns	1.00	0.01	0.1545	0.0010	2.53 KB	1.00
Method_Moq	10	189,569.3 ns	508.32 ns	450.61 ns	255.13	1.76	0.9766	0.7324	18.48 KB	7.30
Method_NSubstitute	10	8,408.7 ns	21.77 ns	18.18 ns	11.32	0.08	0.7324	0.0153	12.07 KB	4.77
Method_FakeItEasy	10	9,301.6 ns	48.44 ns	42.94 ns	12.52	0.10	0.9766	0.0305	16.05 KB	6.34
Method_Imposter	10	1,267.8 ns	5.15 ns	4.30 ns	1.71	0.01	0.3376	0.0057	5.52 KB	2.18
Method_TUnitMocks	10	1,659.4 ns	12.84 ns	11.38 ns	2.23	0.02	0.2747	0.0019	4.49 KB	1.77

Details

BenchmarkDotNet v0.15.8, Linux Ubuntu 24.04.4 LTS (Noble Numbat)

AMD EPYC 7763 2.45GHz, 1 CPU, 4 logical and 2 physical cores

.NET SDK 10.0.203

[Host] : .NET 10.0.7 (10.0.7, 10.0.726.21808), X64 RyuJIT x86-64-v3
Job=InProcess  Toolchain=InProcessEmitToolchain  IterationCount=15

LaunchCount=1  WarmupCount=10

Method	N	Mean	Error	StdDev	Ratio	RatioSD	Gen0	Gen1	Allocated	Alloc Ratio
Property_Mockolate	1	578.4 ns	11.16 ns	10.44 ns	1.00	0.02	0.1574	0.0010	2.58 KB	1.00
Property_Moq	1	11,750.3 ns	84.68 ns	70.71 ns	20.32	0.37	0.6104	-	10.39 KB	4.03
Property_NSubstitute	1	7,708.8 ns	29.84 ns	26.45 ns	13.33	0.24	0.6866	-	11.45 KB	4.44
Property_FakeItEasy	1	8,749.2 ns	33.72 ns	29.89 ns	15.13	0.27	0.6866	-	11.24 KB	4.36
Property_Imposter	1	440.9 ns	11.87 ns	11.11 ns	0.76	0.02	0.1912	0.0019	3.13 KB	1.21
Property_TUnitMocks	1	763.8 ns	3.27 ns	3.06 ns	1.32	0.02	0.1526	0.0010	2.51 KB	0.97
Property_Mockolate	10	1,067.2 ns	7.08 ns	6.27 ns	1.00	0.01	0.1869	-	3.07 KB	1.00
Property_Moq	10	18,679.4 ns	223.28 ns	208.85 ns	17.50	0.21	1.0986	-	18.28 KB	5.95
Property_NSubstitute	10	17,953.4 ns	67.08 ns	56.02 ns	16.82	0.11	1.2817	0.0305	21.08 KB	6.87
Property_FakeItEasy	10	20,938.0 ns	67.92 ns	60.21 ns	19.62	0.12	1.8616	-	30.81 KB	10.03
Property_Imposter	10	1,156.6 ns	9.62 ns	9.00 ns	1.08	0.01	0.2842	0.0019	4.67 KB	1.52
Property_TUnitMocks	10	2,154.4 ns	6.16 ns	4.81 ns	2.02	0.01	0.2823	-	4.66 KB	1.52

Details

BenchmarkDotNet v0.15.8, Linux Ubuntu 24.04.4 LTS (Noble Numbat)

AMD EPYC 7763 2.45GHz, 1 CPU, 4 logical and 2 physical cores

.NET SDK 10.0.203

[Host] : .NET 10.0.7 (10.0.7, 10.0.726.21808), X64 RyuJIT x86-64-v3
Job=InProcess  Toolchain=InProcessEmitToolchain  IterationCount=15

LaunchCount=1  WarmupCount=10

Method	Mean	Error	StdDev	Ratio	RatioSD	Gen0	Gen1	Allocated	Alloc Ratio
Callback_Mockolate	396.3 ns	1.90 ns	1.59 ns	1.00	0.01	0.1197	-	1.96 KB	1.00
Callback_Moq	96,821.0 ns	253.57 ns	237.19 ns	244.30	1.11	0.4883	0.2441	8.88 KB	4.53
Callback_NSubstitute	4,320.4 ns	9.90 ns	8.77 ns	10.90	0.05	0.4730	0.0076	7.74 KB	3.95
Callback_FakeItEasy	4,723.0 ns	15.92 ns	14.12 ns	11.92	0.06	0.4120	0.0153	6.81 KB	3.47
Callback_Imposter	391.9 ns	2.86 ns	2.68 ns	0.99	0.01	0.1454	0.0010	2.38 KB	1.22
Callback_TUnitMocks	591.1 ns	5.14 ns	4.81 ns	1.49	0.01	0.1602	0.0010	2.63 KB	1.34

[github-actions]

Test Results

    21 files  ±0      21 suites  ±0   9m 30s ⏱️ -24s
 3 847 tests +1   3 845 ✅ ±0  1 💤 ±0  1 ❌ +1 
25 055 runs  +3  25 052 ✅ +1  1 💤 ±0  2 ❌ +2 

For more details on these failures, see this check.

Results for commit a58449d. ± Comparison against base commit 22dfeb1.

♻️ This comment has been updated with latest results.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
100.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud