Replace regex-based metadata expansion with manual scanning by DustinCampbell · Pull Request #14116 · dotnet/msbuild

DustinCampbell · 2026-06-19T21:30:24Z

Summary

Replaces the regex-based metadata expansion in the Expander with a zero-allocation ref struct scanner that performs manual character parsing. This eliminates the Regex.Replace call and associated MatchEvaluator delegate allocations that occurred on every metadata expression expansion.

Changes

Removed Expander.MetadataMatchEvaluator.cs and Expander.RegularExpressions.cs — regex infrastructure is no longer needed
Rewrote Expander.MetadataExpander.cs using a ref struct scanner that walks the expression character-by-character, identifying %(...) patterns without allocating
Simplified MetadataMatch, MetadataMatchType, and OneOrMultipleMetadataMatches structs
Added ExpanderBenchmark.cs with 18 benchmarks covering property, item, metadata, and mixed expansion scenarios

Benchmark Results

.NET 10.0 (PropertyCount=10, ItemCount=10)

Benchmark	Baseline	After	Speedup	Alloc Before	Alloc After
Metadata_Unqualified	413 ns	124 ns	3.3×	624 B	0 B
Metadata_Qualified	496 ns	208 ns	2.4×	736 B	48 B
Metadata_Multiple	765 ns	240 ns	3.2×	1,248 B	0 B
Mixed_PropertyAndMetadata	1,010 ns	489 ns	2.1×	1,248 B	0 B
Mixed_All	3,108 ns	2,580 ns	1.2×	1,880 B	1,352 B
ItemList_WithTransform	2,918 ns	2,823 ns	1.03×	1,376 B	1,024 B

.NET Framework 4.7.2 (PropertyCount=10, ItemCount=10)

Benchmark	Baseline	After	Speedup	Alloc Before	Alloc After
Metadata_Unqualified	2,051 ns	814 ns	2.5×	369 B	0 B
Metadata_Qualified	1,847 ns	1,035 ns	1.8×	453 B	40 B
Metadata_Multiple	3,662 ns	1,239 ns	3.0×	741 B	0 B
Mixed_PropertyAndMetadata	4,819 ns	2,303 ns	2.1×	741 B	0 B
Mixed_All	16,015 ns	12,282 ns	1.3×	1,494 B	1,170 B
ItemList_WithTransform	13,503 ns	12,834 ns	1.05×	1,186 B	962 B

.NET 10.0 Baseline (before changes)

Method	PropertyCount	ItemCount	Mean	Error	StdDev	Ratio	RatioSD	Gen0	Allocated	Alloc Ratio
Property_Single	10	10	130.98 ns	0.275 ns	0.257 ns	2.73	0.01	-	-	NA
Property_Multiple	10	10	423.68 ns	0.551 ns	0.488 ns	8.83	0.01	-	-	NA
Property_Nested	10	10	319.84 ns	0.432 ns	0.360 ns	6.67	0.01	-	-	NA
Property_Concatenation	10	10	492.58 ns	1.423 ns	1.331 ns	10.27	0.03	0.0019	40 B	NA
ItemList_Simple	10	10	997.20 ns	2.848 ns	2.664 ns	20.79	0.06	0.0153	280 B	NA
ItemList_WithTransform	10	10	2,917.91 ns	7.731 ns	7.232 ns	60.84	0.16	0.0801	1376 B	NA
ItemList_WithSeparator	10	10	738.21 ns	2.974 ns	2.636 ns	15.40	0.06	0.0458	768 B	NA
Metadata_Unqualified	10	10	413.46 ns	5.774 ns	5.401 ns	8.63	0.12	0.0372	624 B	NA
Metadata_Qualified	10	10	496.08 ns	5.581 ns	5.221 ns	10.35	0.12	0.0439	736 B	NA
Metadata_Multiple	10	10	764.50 ns	5.600 ns	4.965 ns	15.94	0.11	0.0744	1248 B	NA
Mixed_PropertyAndItem	10	10	1,968.60 ns	4.641 ns	4.114 ns	41.04	0.10	0.0572	1016 B	NA
Mixed_PropertyAndMetadata	10	10	1,009.99 ns	6.146 ns	5.749 ns	21.07	0.11	0.0744	1248 B	NA
Mixed_All	10	10	3,108.21 ns	14.037 ns	13.130 ns	64.77	0.28	0.1106	1880 B	NA
NoExpansion	10	10	47.96 ns	0.038 ns	0.032 ns	1.00	0.00	-	-	NA
PropertyAndUnescape_Multiple	10	10	423.10 ns	0.605 ns	0.506 ns	8.82	0.01	-	-	NA
ItemListAndUnescape_WithTransform	10	10	2,856.03 ns	9.655 ns	9.032 ns	59.55	0.21	0.0801	1376 B	NA
MetadataAndUnescape_Multiple	10	10	789.42 ns	7.125 ns	6.665 ns	16.46	0.15	0.0744	1248 B	NA
MixedAndUnescape_All	10	10	3,048.62 ns	9.876 ns	9.238 ns	63.61	0.20	0.1106	1880 B	NA

Property_Single	10	100	139.11 ns	0.147 ns	0.130 ns	3.03	0.01	-	-	NA
Property_Multiple	10	100	439.69 ns	0.444 ns	0.393 ns	9.57	0.02	-	-	NA
Property_Nested	10	100	303.68 ns	0.685 ns	0.607 ns	6.61	0.02	-	-	NA
Property_Concatenation	10	100	615.62 ns	1.369 ns	1.281 ns	13.40	0.03	0.0019	40 B	NA
ItemList_Simple	10	100	5,554.81 ns	7.731 ns	6.456 ns	120.86	0.27	0.0992	1720 B	NA
ItemList_WithTransform	10	100	20,013.65 ns	63.738 ns	56.502 ns	435.48	1.19	0.4578	7857 B	NA
ItemList_WithSeparator	10	100	4,297.85 ns	50.904 ns	47.615 ns	93.52	1.00	0.3357	5624 B	NA
Metadata_Unqualified	10	100	397.81 ns	2.257 ns	2.111 ns	8.66	0.05	0.0372	624 B	NA
Metadata_Qualified	10	100	510.99 ns	6.103 ns	5.709 ns	11.12	0.13	0.0439	736 B	NA
Metadata_Multiple	10	100	791.16 ns	6.240 ns	5.837 ns	17.22	0.12	0.0744	1248 B	NA
Mixed_PropertyAndItem	10	100	13,870.06 ns	25.805 ns	24.138 ns	301.82	0.65	0.4425	7497 B	NA
Mixed_PropertyAndMetadata	10	100	1,032.05 ns	6.635 ns	5.881 ns	22.46	0.13	0.0744	1248 B	NA
Mixed_All	10	100	15,326.58 ns	59.059 ns	55.244 ns	333.51	1.16	0.4883	8361 B	NA
NoExpansion	10	100	45.95 ns	0.074 ns	0.070 ns	1.00	0.00	-	-	NA
PropertyAndUnescape_Multiple	10	100	423.40 ns	1.032 ns	0.915 ns	9.21	0.03	-	-	NA
ItemListAndUnescape_WithTransform	10	100	19,798.50 ns	51.048 ns	47.750 ns	430.82	0.96	0.4578	7857 B	NA
MetadataAndUnescape_Multiple	10	100	804.85 ns	5.537 ns	5.179 ns	17.51	0.11	0.0744	1248 B	NA
MixedAndUnescape_All	10	100	15,391.75 ns	30.076 ns	26.661 ns	334.91	0.88	0.4883	8361 B	NA

Property_Single	100	10	117.50 ns	0.187 ns	0.166 ns	2.41	0.00	-	-	NA
Property_Multiple	100	10	409.40 ns	0.376 ns	0.314 ns	8.41	0.02	-	-	NA
Property_Nested	100	10	307.79 ns	0.414 ns	0.387 ns	6.32	0.01	-	-	NA
Property_Concatenation	100	10	481.39 ns	0.881 ns	0.736 ns	9.89	0.03	0.0019	40 B	NA
ItemList_Simple	100	10	1,011.21 ns	4.075 ns	3.812 ns	20.77	0.09	0.0153	280 B	NA
ItemList_WithTransform	100	10	2,902.73 ns	7.269 ns	6.799 ns	59.61	0.17	0.0801	1376 B	NA
ItemList_WithSeparator	100	10	752.80 ns	6.447 ns	6.030 ns	15.46	0.12	0.0458	768 B	NA
Metadata_Unqualified	100	10	408.72 ns	4.095 ns	3.830 ns	8.39	0.08	0.0372	624 B	NA
Metadata_Qualified	100	10	509.34 ns	3.895 ns	3.453 ns	10.46	0.06	0.0439	736 B	NA
Metadata_Multiple	100	10	870.89 ns	3.096 ns	2.745 ns	17.88	0.07	0.0744	1248 B	NA
Mixed_PropertyAndItem	100	10	1,994.54 ns	17.956 ns	16.796 ns	40.96	0.36	0.0572	1016 B	NA
Mixed_PropertyAndMetadata	100	10	1,056.35 ns	7.394 ns	6.916 ns	21.69	0.15	0.0744	1248 B	NA
Mixed_All	100	10	3,111.84 ns	12.118 ns	11.335 ns	63.91	0.24	0.1106	1880 B	NA
NoExpansion	100	10	48.69 ns	0.078 ns	0.073 ns	1.00	0.00	-	-	NA
PropertyAndUnescape_Multiple	100	10	413.89 ns	0.628 ns	0.557 ns	8.50	0.02	-	-	NA
ItemListAndUnescape_WithTransform	100	10	2,844.84 ns	8.383 ns	7.841 ns	58.43	0.21	0.0801	1376 B	NA
MetadataAndUnescape_Multiple	100	10	777.41 ns	13.765 ns	12.202 ns	15.96	0.27	0.0744	1248 B	NA
MixedAndUnescape_All	100	10	3,107.62 ns	7.542 ns	7.055 ns	63.82	0.15	0.1106	1880 B	NA

Property_Single	100	100	124.15 ns	0.141 ns	0.132 ns	2.69	0.00	-	-	NA
Property_Multiple	100	100	425.65 ns	0.369 ns	0.346 ns	9.23	0.01	-	-	NA
Property_Nested	100	100	327.94 ns	0.579 ns	0.541 ns	7.11	0.01	-	-	NA
Property_Concatenation	100	100	506.00 ns	0.876 ns	0.731 ns	10.98	0.02	0.0019	40 B	NA
ItemList_Simple	100	100	5,652.04 ns	14.408 ns	13.477 ns	122.62	0.32	0.0992	1720 B	NA
ItemList_WithTransform	100	100	20,064.34 ns	73.123 ns	68.399 ns	435.30	1.52	0.4578	7857 B	NA
ItemList_WithSeparator	100	100	4,319.37 ns	50.762 ns	47.483 ns	93.71	1.06	0.3357	5624 B	NA
Metadata_Unqualified	100	100	429.14 ns	2.539 ns	2.375 ns	9.31	0.05	0.0372	624 B	NA
Metadata_Qualified	100	100	518.28 ns	4.242 ns	3.968 ns	11.24	0.08	0.0439	736 B	NA
Metadata_Multiple	100	100	761.81 ns	3.667 ns	3.430 ns	16.53	0.08	0.0744	1248 B	NA
Mixed_PropertyAndItem	100	100	13,770.44 ns	30.492 ns	28.523 ns	298.75	0.57	0.4425	7497 B	NA
Mixed_PropertyAndMetadata	100	100	1,040.45 ns	5.724 ns	5.074 ns	22.57	0.12	0.0744	1248 B	NA
Mixed_All	100	100	14,727.39 ns	40.882 ns	36.241 ns	319.50	0.79	0.4883	8361 B	NA
NoExpansion	100	100	46.09 ns	0.045 ns	0.042 ns	1.00	0.00	-	-	NA
PropertyAndUnescape_Multiple	100	100	415.13 ns	0.620 ns	0.550 ns	9.01	0.02	-	-	NA
ItemListAndUnescape_WithTransform	100	100	19,807.96 ns	46.244 ns	40.994 ns	429.72	0.80	0.4578	7857 B	NA
MetadataAndUnescape_Multiple	100	100	764.30 ns	8.365 ns	7.824 ns	16.58	0.17	0.0744	1248 B	NA
MixedAndUnescape_All	100	100	15,170.88 ns	145.082 ns	135.710 ns	329.14	2.94	0.4883	8361 B	NA

.NET 10.0 (after changes)

Method	PropertyCount	ItemCount	Mean	Error	StdDev	Ratio	RatioSD	Gen0	Allocated	Alloc Ratio
Property_Single	10	10	124.34 ns	0.974 ns	0.813 ns	2.90	0.02	-	-	NA
Property_Multiple	10	10	414.88 ns	0.534 ns	0.499 ns	9.66	0.02	-	-	NA
Property_Nested	10	10	313.44 ns	0.313 ns	0.293 ns	7.30	0.02	-	-	NA
Property_Concatenation	10	10	498.45 ns	0.396 ns	0.331 ns	11.61	0.03	0.0019	40 B	NA
ItemList_Simple	10	10	1,071.81 ns	5.265 ns	4.397 ns	24.96	0.12	0.0153	280 B	NA
ItemList_WithTransform	10	10	2,822.97 ns	5.025 ns	4.700 ns	65.74	0.15	0.0610	1024 B	NA
ItemList_WithSeparator	10	10	754.58 ns	3.282 ns	3.070 ns	17.58	0.07	0.0458	768 B	NA
Metadata_Unqualified	10	10	123.65 ns	0.502 ns	0.445 ns	2.88	0.01	-	-	NA
Metadata_Qualified	10	10	208.18 ns	0.402 ns	0.376 ns	4.85	0.01	0.0029	48 B	NA
Metadata_Multiple	10	10	239.93 ns	0.155 ns	0.137 ns	5.59	0.01	-	-	NA
Mixed_PropertyAndItem	10	10	1,995.66 ns	5.939 ns	5.265 ns	46.48	0.20	0.0572	1016 B	NA
Mixed_PropertyAndMetadata	10	10	488.77 ns	1.876 ns	1.663 ns	11.38	0.04	-	-	NA
Mixed_All	10	10	2,580.41 ns	9.309 ns	8.708 ns	60.11	0.25	0.0801	1352 B	NA
NoExpansion	10	10	42.94 ns	0.102 ns	0.090 ns	1.00	0.00	-	-	NA
PropertyAndUnescape_Multiple	10	10	431.96 ns	1.475 ns	1.380 ns	10.06	0.05	-	-	NA
ItemListAndUnescape_WithTransform	10	10	2,677.23 ns	6.504 ns	5.766 ns	62.35	0.16	0.0610	1024 B	NA
MetadataAndUnescape_Multiple	10	10	259.95 ns	0.466 ns	0.413 ns	6.05	0.02	-	-	NA
MixedAndUnescape_All	10	10	2,534.57 ns	7.239 ns	6.417 ns	59.03	0.18	0.0801	1352 B	NA

Property_Single	10	100	123.49 ns	0.337 ns	0.299 ns	3.02	0.01	-	-	NA
Property_Multiple	10	100	424.91 ns	0.881 ns	0.824 ns	10.40	0.02	-	-	NA
Property_Nested	10	100	310.78 ns	0.960 ns	0.898 ns	7.61	0.02	-	-	NA
Property_Concatenation	10	100	482.49 ns	1.242 ns	1.037 ns	11.81	0.03	0.0019	40 B	NA
ItemList_Simple	10	100	5,637.35 ns	12.281 ns	11.488 ns	137.98	0.36	0.0992	1720 B	NA
ItemList_WithTransform	10	100	20,394.70 ns	43.186 ns	40.397 ns	499.09	1.10	0.4272	7505 B	NA
ItemList_WithSeparator	10	100	4,257.52 ns	26.233 ns	24.539 ns	104.20	0.64	0.3357	5624 B	NA
Metadata_Unqualified	10	100	129.49 ns	0.849 ns	0.794 ns	3.17	0.02	-	-	NA
Metadata_Qualified	10	100	204.93 ns	0.658 ns	0.549 ns	5.02	0.01	0.0029	48 B	NA
Metadata_Multiple	10	100	249.55 ns	0.498 ns	0.441 ns	6.11	0.01	-	-	NA
Mixed_PropertyAndItem	10	100	13,819.14 ns	34.942 ns	32.685 ns	338.29	1.00	0.4425	7497 B	NA
Mixed_PropertyAndMetadata	10	100	471.89 ns	0.792 ns	0.702 ns	11.55	0.02	-	-	NA
Mixed_All	10	100	14,365.34 ns	68.962 ns	61.133 ns	351.62	1.51	0.4578	7833 B	NA
NoExpansion	10	100	40.85 ns	0.045 ns	0.040 ns	1.00	0.00	-	-	NA
PropertyAndUnescape_Multiple	10	100	432.32 ns	0.341 ns	0.302 ns	10.58	0.01	-	-	NA
ItemListAndUnescape_WithTransform	10	100	19,739.02 ns	101.838 ns	85.039 ns	483.10	2.21	0.4272	7505 B	NA
MetadataAndUnescape_Multiple	10	100	257.78 ns	0.392 ns	0.347 ns	6.31	0.01	-	-	NA
MixedAndUnescape_All	10	100	15,015.87 ns	126.842 ns	112.442 ns	367.54	2.66	0.4578	7833 B	NA

Property_Single	100	10	116.61 ns	0.090 ns	0.079 ns	2.68	0.00	-	-	NA
Property_Multiple	100	10	408.72 ns	0.454 ns	0.379 ns	9.39	0.01	-	-	NA
Property_Nested	100	10	301.06 ns	0.242 ns	0.214 ns	6.92	0.01	-	-	NA
Property_Concatenation	100	10	504.98 ns	0.771 ns	0.684 ns	11.60	0.03	0.0019	40 B	NA
ItemList_Simple	100	10	1,048.81 ns	3.220 ns	3.012 ns	24.09	0.08	0.0153	280 B	NA
ItemList_WithTransform	100	10	2,684.65 ns	4.002 ns	3.547 ns	61.67	0.14	0.0610	1024 B	NA
ItemList_WithSeparator	100	10	756.66 ns	3.902 ns	3.459 ns	17.38	0.08	0.0458	768 B	NA
Metadata_Unqualified	100	10	123.83 ns	0.359 ns	0.318 ns	2.84	0.01	-	-	NA
Metadata_Qualified	100	10	209.00 ns	0.193 ns	0.162 ns	4.80	0.01	0.0029	48 B	NA
Metadata_Multiple	100	10	242.31 ns	0.328 ns	0.307 ns	5.57	0.01	-	-	NA
Mixed_PropertyAndItem	100	10	1,993.14 ns	7.872 ns	6.574 ns	45.79	0.17	0.0572	1016 B	NA
Mixed_PropertyAndMetadata	100	10	509.55 ns	1.098 ns	1.027 ns	11.70	0.04	-	-	NA
Mixed_All	100	10	2,635.95 ns	10.728 ns	10.035 ns	60.55	0.25	0.0801	1352 B	NA
NoExpansion	100	10	43.53 ns	0.061 ns	0.057 ns	1.00	0.00	-	-	NA
PropertyAndUnescape_Multiple	100	10	410.32 ns	0.288 ns	0.241 ns	9.43	0.01	-	-	NA
ItemListAndUnescape_WithTransform	100	10	2,662.43 ns	5.198 ns	4.341 ns	61.16	0.14	0.0610	1024 B	NA
MetadataAndUnescape_Multiple	100	10	250.08 ns	0.328 ns	0.307 ns	5.74	0.01	-	-	NA
MixedAndUnescape_All	100	10	2,606.68 ns	8.508 ns	7.958 ns	59.88	0.21	0.0801	1352 B	NA

Property_Single	100	100	122.37 ns	0.151 ns	0.134 ns	2.93	0.01	-	-	NA
Property_Multiple	100	100	408.56 ns	0.369 ns	0.328 ns	9.79	0.01	-	-	NA
Property_Nested	100	100	312.80 ns	0.519 ns	0.486 ns	7.50	0.01	-	-	NA
Property_Concatenation	100	100	466.24 ns	0.454 ns	0.403 ns	11.18	0.01	0.0024	40 B	NA
ItemList_Simple	100	100	5,605.19 ns	14.293 ns	13.369 ns	134.38	0.37	0.0992	1720 B	NA
ItemList_WithTransform	100	100	20,586.52 ns	43.470 ns	38.535 ns	493.51	1.13	0.4272	7505 B	NA
ItemList_WithSeparator	100	100	4,314.38 ns	20.992 ns	18.609 ns	103.43	0.47	0.3357	5624 B	NA
Metadata_Unqualified	100	100	120.59 ns	0.106 ns	0.088 ns	2.89	0.00	-	-	NA
Metadata_Qualified	100	100	210.77 ns	0.279 ns	0.261 ns	5.05	0.01	0.0029	48 B	NA
Metadata_Multiple	100	100	238.57 ns	0.204 ns	0.181 ns	5.72	0.01	-	-	NA
Mixed_PropertyAndItem	100	100	14,010.69 ns	38.157 ns	35.692 ns	335.89	1.05	0.4425	7497 B	NA
Mixed_PropertyAndMetadata	100	100	479.25 ns	0.709 ns	0.629 ns	11.49	0.02	-	-	NA
Mixed_All	100	100	14,438.36 ns	60.947 ns	57.010 ns	346.14	1.32	0.4578	7833 B	NA
NoExpansion	100	100	41.71 ns	0.048 ns	0.045 ns	1.00	0.00	-	-	NA
PropertyAndUnescape_Multiple	100	100	412.33 ns	0.414 ns	0.367 ns	9.88	0.01	-	-	NA
ItemListAndUnescape_WithTransform	100	100	20,168.04 ns	38.600 ns	32.232 ns	483.54	0.80	0.4272	7505 B	NA
MetadataAndUnescape_Multiple	100	100	244.83 ns	0.479 ns	0.424 ns	5.87	0.01	-	-	NA
MixedAndUnescape_All	100	100	14,591.08 ns	40.316 ns	37.711 ns	349.81	0.97	0.4578	7833 B	NA

.NET Framework 4.7.2 Baseline (before changes)

Method	PropertyCount	ItemCount	Mean	Error	StdDev	Ratio	RatioSD	Gen0	Gen1	Allocated	Alloc Ratio
Property_Single	10	10	517.3 ns	1.39 ns	1.30 ns	1.36	0.01	-	-	-	NA
Property_Multiple	10	10	1,830.9 ns	3.31 ns	3.10 ns	4.80	0.02	-	-	-	NA
Property_Nested	10	10	1,297.8 ns	2.50 ns	2.34 ns	3.40	0.01	-	-	-	NA
Property_Concatenation	10	10	1,994.8 ns	2.75 ns	2.44 ns	5.23	0.02	0.0038	-	28 B	NA
ItemList_Simple	10	10	2,802.3 ns	5.45 ns	4.83 ns	7.34	0.03	0.0267	-	152 B	NA
ItemList_WithTransform	10	10	13,503.0 ns	17.63 ns	16.49 ns	35.39	0.11	0.2136	-	1186 B	NA
ItemList_WithSeparator	10	10	2,195.0 ns	7.66 ns	7.17 ns	5.75	0.03	0.1106	-	593 B	NA
Metadata_Unqualified	10	10	2,051.3 ns	6.27 ns	5.56 ns	5.38	0.02	0.0687	-	369 B	NA
Metadata_Qualified	10	10	1,847.0 ns	5.00 ns	4.43 ns	4.84	0.02	0.0858	-	453 B	NA
Metadata_Multiple	10	10	3,661.5 ns	14.93 ns	13.97 ns	9.59	0.04	0.1411	-	741 B	NA
Mixed_PropertyAndItem	10	10	9,906.0 ns	24.44 ns	22.86 ns	25.96	0.10	0.1678	-	954 B	NA
Mixed_PropertyAndMetadata	10	10	4,819.4 ns	10.91 ns	10.20 ns	12.63	0.04	0.1373	-	741 B	NA
Mixed_All	10	10	16,014.6 ns	85.04 ns	79.55 ns	41.96	0.27	0.2747	-	1494 B	NA
NoExpansion	10	10	381.6 ns	1.27 ns	1.12 ns	1.00	0.00	-	-	-	NA
PropertyAndUnescape_Multiple	10	10	1,822.8 ns	3.55 ns	3.14 ns	4.78	0.02	-	-	-	NA
ItemListAndUnescape_WithTransform	10	10	13,870.9 ns	10.20 ns	9.04 ns	36.35	0.11	0.2136	-	1186 B	NA
MetadataAndUnescape_Multiple	10	10	3,688.4 ns	8.75 ns	7.76 ns	9.67	0.04	0.1411	-	741 B	NA
MixedAndUnescape_All	10	10	15,915.3 ns	49.95 ns	46.73 ns	41.72	0.19	0.2747	-	1494 B	NA

Property_Single	10	100	524.0 ns	0.86 ns	0.76 ns	1.31	0.00	-	-	-	NA
Property_Multiple	10	100	1,764.5 ns	2.78 ns	2.46 ns	4.40	0.01	-	-	-	NA
Property_Nested	10	100	1,313.3 ns	2.01 ns	1.88 ns	3.27	0.01	-	-	-	NA
Property_Concatenation	10	100	2,058.0 ns	1.98 ns	1.76 ns	5.13	0.01	0.0038	-	28 B	NA
ItemList_Simple	10	100	19,465.9 ns	27.03 ns	22.57 ns	48.51	0.11	0.1526	-	874 B	NA
ItemList_WithTransform	10	100	108,475.2 ns	109.36 ns	96.95 ns	270.37	0.60	1.4648	-	8040 B	NA
ItemList_WithSeparator	10	100	10,791.8 ns	44.90 ns	39.80 ns	26.90	0.10	1.7395	0.0305	9162 B	NA
Metadata_Unqualified	10	100	2,030.2 ns	7.42 ns	6.57 ns	5.06	0.02	0.0687	-	369 B	NA
Metadata_Qualified	10	100	1,803.5 ns	6.41 ns	6.00 ns	4.49	0.02	0.0858	-	453 B	NA
Metadata_Multiple	10	100	3,679.5 ns	7.44 ns	6.21 ns	9.17	0.02	0.1411	-	741 B	NA
Mixed_PropertyAndItem	10	100	73,272.7 ns	123.33 ns	115.36 ns	182.66	0.41	1.4648	-	7806 B	NA
Mixed_PropertyAndMetadata	10	100	4,756.1 ns	13.57 ns	11.33 ns	11.85	0.04	0.1373	-	741 B	NA
Mixed_All	10	100	80,697.1 ns	199.66 ns	186.77 ns	201.13	0.69	1.5869	-	8347 B	NA
NoExpansion	10	100	401.2 ns	0.87 ns	0.77 ns	1.00	0.00	-	-	-	NA
PropertyAndUnescape_Multiple	10	100	1,863.1 ns	2.16 ns	2.02 ns	4.64	0.01	-	-	-	NA
ItemListAndUnescape_WithTransform	10	100	109,868.9 ns	89.80 ns	79.60 ns	273.84	0.64	1.4648	-	8040 B	NA
MetadataAndUnescape_Multiple	10	100	3,713.7 ns	11.78 ns	10.45 ns	9.26	0.04	0.1411	-	741 B	NA
MixedAndUnescape_All	10	100	79,224.1 ns	171.90 ns	160.79 ns	197.44	0.57	1.5869	-	8347 B	NA

Property_Single	100	10	475.3 ns	1.62 ns	1.52 ns	1.14	0.00	-	-	-	NA
Property_Multiple	100	10	1,847.0 ns	12.50 ns	11.69 ns	4.41	0.03	-	-	-	NA
Property_Nested	100	10	1,323.3 ns	5.85 ns	5.47 ns	3.16	0.01	-	-	-	NA
Property_Concatenation	100	10	1,984.2 ns	2.65 ns	2.35 ns	4.74	0.01	0.0038	-	28 B	NA
ItemList_Simple	100	10	2,831.1 ns	8.30 ns	7.36 ns	6.76	0.01	0.0267	-	152 B	NA
ItemList_WithTransform	100	10	13,579.8 ns	20.64 ns	19.31 ns	32.44	0.05	0.2136	-	1186 B	NA
ItemList_WithSeparator	100	10	2,200.6 ns	11.09 ns	10.37 ns	5.26	0.03	0.1106	-	593 B	NA
Metadata_Unqualified	100	10	2,045.4 ns	9.43 ns	8.82 ns	4.89	0.02	0.0687	-	369 B	NA
Metadata_Qualified	100	10	1,837.9 ns	2.97 ns	2.78 ns	4.39	0.01	0.0858	-	453 B	NA
Metadata_Multiple	100	10	3,731.1 ns	12.22 ns	10.83 ns	8.91	0.03	0.1411	-	741 B	NA
Mixed_PropertyAndItem	100	10	9,830.4 ns	11.09 ns	10.37 ns	23.49	0.04	0.1678	-	954 B	NA
Mixed_PropertyAndMetadata	100	10	4,738.0 ns	15.02 ns	14.05 ns	11.32	0.04	0.1373	-	741 B	NA
Mixed_All	100	10	15,860.6 ns	101.16 ns	94.63 ns	37.89	0.23	0.2747	-	1494 B	NA
NoExpansion	100	10	418.6 ns	0.58 ns	0.51 ns	1.00	0.00	-	-	-	NA
PropertyAndUnescape_Multiple	100	10	1,716.3 ns	2.59 ns	2.42 ns	4.10	0.01	-	-	-	NA
ItemListAndUnescape_WithTransform	100	10	13,757.1 ns	17.09 ns	15.15 ns	32.86	0.05	0.2136	-	1186 B	NA
MetadataAndUnescape_Multiple	100	10	3,673.5 ns	16.77 ns	15.68 ns	8.78	0.04	0.1411	-	741 B	NA
MixedAndUnescape_All	100	10	16,036.5 ns	91.64 ns	85.72 ns	38.29	0.22	0.2747	-	1494 B	NA

Property_Single	100	100	505.9 ns	1.64 ns	1.53 ns	1.29	0.00	-	-	-	NA
Property_Multiple	100	100	1,841.7 ns	3.50 ns	3.28 ns	4.71	0.01	-	-	-	NA
Property_Nested	100	100	1,274.6 ns	2.80 ns	2.34 ns	3.26	0.01	-	-	-	NA
Property_Concatenation	100	100	2,066.2 ns	2.68 ns	2.38 ns	5.28	0.01	0.0038	-	28 B	NA
ItemList_Simple	100	100	19,683.2 ns	95.50 ns	89.33 ns	50.31	0.19	0.1526	-	874 B	NA
ItemList_WithTransform	100	100	109,411.0 ns	110.15 ns	91.98 ns	279.65	0.46	1.4648	-	8040 B	NA
ItemList_WithSeparator	100	100	10,842.9 ns	25.85 ns	22.92 ns	27.71	0.05	1.7395	0.0305	9162 B	NA
Metadata_Unqualified	100	100	2,071.2 ns	7.69 ns	7.19 ns	5.29	0.02	0.0687	-	369 B	NA
Metadata_Qualified	100	100	1,836.9 ns	3.43 ns	2.86 ns	4.70	0.01	0.0858	-	453 B	NA
Metadata_Multiple	100	100	3,709.8 ns	23.46 ns	21.94 ns	9.47	0.05	0.1411	-	741 B	NA
Mixed_PropertyAndItem	100	100	72,283.2 ns	121.62 ns	113.77 ns	184.71	0.39	1.4648	-	7806 B	NA
Mixed_PropertyAndMetadata	100	100	4,800.7 ns	11.54 ns	10.79 ns	12.28	0.03	0.1373	-	741 B	NA
Mixed_All	100	100	78,998.2 ns	149.92 ns	140.23 ns	201.94	0.43	1.5869	-	8347 B	NA
NoExpansion	100	100	391.3 ns	0.54 ns	0.42 ns	1.00	0.00	-	-	-	NA
PropertyAndUnescape_Multiple	100	100	1,702.7 ns	2.66 ns	2.49 ns	4.35	0.01	-	-	-	NA
ItemListAndUnescape_WithTransform	100	100	110,106.0 ns	167.29 ns	156.48 ns	281.45	0.46	1.4648	-	8040 B	NA
MetadataAndUnescape_Multiple	100	100	3,694.7 ns	20.10 ns	16.79 ns	9.44	0.04	0.1411	-	741 B	NA
MixedAndUnescape_All	100	100	79,275.3 ns	138.66 ns	129.70 ns	202.56	0.43	1.5869	-	8347 B	NA

.NET Framework 4.7.2 (after changes)

Method	PropertyCount	ItemCount	Mean	Error	StdDev	Ratio	RatioSD	Gen0	Gen1	Allocated	Alloc Ratio
Property_Single	10	10	513.0 ns	1.60 ns	1.50 ns	1.36	0.00	-	-	-	NA
Property_Multiple	10	10	1,827.2 ns	5.72 ns	5.35 ns	4.83	0.01	-	-	-	NA
Property_Nested	10	10	1,286.4 ns	6.58 ns	6.15 ns	3.40	0.02	-	-	-	NA
Property_Concatenation	10	10	2,032.8 ns	2.62 ns	2.32 ns	5.37	0.01	0.0038	-	28 B	NA
ItemList_Simple	10	10	2,776.7 ns	4.29 ns	3.80 ns	7.34	0.02	0.0267	-	152 B	NA
ItemList_WithTransform	10	10	12,833.9 ns	13.45 ns	12.58 ns	33.93	0.06	0.1831	-	962 B	NA
ItemList_WithSeparator	10	10	2,195.2 ns	8.23 ns	7.70 ns	5.81	0.02	0.1106	-	593 B	NA
Metadata_Unqualified	10	10	814.4 ns	2.89 ns	2.70 ns	2.15	0.01	-	-	-	NA
Metadata_Qualified	10	10	1,034.7 ns	4.00 ns	3.54 ns	2.74	0.01	0.0076	-	40 B	NA
Metadata_Multiple	10	10	1,238.8 ns	2.76 ns	2.58 ns	3.28	0.01	-	-	-	NA
Mixed_PropertyAndItem	10	10	9,797.2 ns	26.78 ns	25.05 ns	25.91	0.07	0.1678	-	954 B	NA
Mixed_PropertyAndMetadata	10	10	2,302.8 ns	4.33 ns	3.61 ns	6.09	0.01	-	-	-	NA
Mixed_All	10	10	12,282.4 ns	12.91 ns	11.45 ns	32.47	0.07	0.2136	-	1170 B	NA
NoExpansion	10	10	378.2 ns	0.68 ns	0.60 ns	1.00	0.00	-	-	-	NA
PropertyAndUnescape_Multiple	10	10	1,826.4 ns	3.30 ns	3.09 ns	4.83	0.01	-	-	-	NA
ItemListAndUnescape_WithTransform	10	10	12,832.7 ns	21.78 ns	19.30 ns	33.93	0.07	0.1831	-	962 B	NA
MetadataAndUnescape_Multiple	10	10	1,258.7 ns	4.24 ns	3.97 ns	3.33	0.01	-	-	-	NA
MixedAndUnescape_All	10	10	12,285.8 ns	24.43 ns	20.40 ns	32.48	0.07	0.2136	-	1170 B	NA

Property_Single	10	100	532.5 ns	1.59 ns	1.41 ns	1.43	0.00	-	-	-	NA
Property_Multiple	10	100	1,766.5 ns	2.20 ns	1.95 ns	4.75	0.01	-	-	-	NA
Property_Nested	10	100	1,233.6 ns	1.78 ns	1.49 ns	3.32	0.01	-	-	-	NA
Property_Concatenation	10	100	1,980.7 ns	5.00 ns	4.68 ns	5.33	0.02	0.0038	-	28 B	NA
ItemList_Simple	10	100	19,412.5 ns	34.23 ns	30.34 ns	52.20	0.18	0.1526	-	874 B	NA
ItemList_WithTransform	10	100	110,069.7 ns	199.78 ns	186.88 ns	295.99	0.88	1.4648	-	7816 B	NA
ItemList_WithSeparator	10	100	10,760.2 ns	25.72 ns	21.48 ns	28.93	0.10	1.7395	0.0305	9162 B	NA
Metadata_Unqualified	10	100	807.6 ns	1.96 ns	1.83 ns	2.17	0.01	-	-	-	NA
Metadata_Qualified	10	100	1,022.9 ns	3.49 ns	3.27 ns	2.75	0.01	0.0076	-	40 B	NA
Metadata_Multiple	10	100	1,266.5 ns	2.76 ns	2.58 ns	3.41	0.01	-	-	-	NA
Mixed_PropertyAndItem	10	100	72,398.3 ns	75.22 ns	62.81 ns	194.66	0.70	1.4648	-	7806 B	NA
Mixed_PropertyAndMetadata	10	100	2,313.9 ns	5.86 ns	5.20 ns	6.22	0.02	-	-	-	NA
Mixed_All	10	100	74,906.8 ns	122.30 ns	114.40 ns	201.43	0.66	1.4648	-	8022 B	NA
NoExpansion	10	100	371.9 ns	1.20 ns	1.12 ns	1.00	0.00	-	-	-	NA
PropertyAndUnescape_Multiple	10	100	1,807.0 ns	10.32 ns	9.65 ns	4.86	0.02	-	-	-	NA
ItemListAndUnescape_WithTransform	10	100	112,803.3 ns	138.70 ns	115.82 ns	303.30	0.99	1.4648	-	7816 B	NA
MetadataAndUnescape_Multiple	10	100	1,269.4 ns	5.50 ns	4.88 ns	3.41	0.02	-	-	-	NA
MixedAndUnescape_All	10	100	75,341.4 ns	132.80 ns	124.22 ns	202.60	0.70	1.4648	-	8022 B	NA

Property_Single	100	10	455.8 ns	0.67 ns	0.59 ns	1.16	0.00	-	-	-	NA
Property_Multiple	100	10	1,712.4 ns	2.59 ns	2.29 ns	4.36	0.01	-	-	-	NA
Property_Nested	100	10	1,248.5 ns	1.89 ns	1.67 ns	3.18	0.00	-	-	-	NA
Property_Concatenation	100	10	2,024.9 ns	2.77 ns	2.59 ns	5.16	0.01	0.0038	-	28 B	NA
ItemList_Simple	100	10	2,767.7 ns	5.69 ns	5.32 ns	7.05	0.02	0.0267	-	152 B	NA
ItemList_WithTransform	100	10	12,855.3 ns	16.95 ns	15.85 ns	32.73	0.07	0.1831	-	962 B	NA
ItemList_WithSeparator	100	10	2,159.0 ns	6.96 ns	6.51 ns	5.50	0.02	0.1106	-	593 B	NA
Metadata_Unqualified	100	10	839.3 ns	4.88 ns	4.56 ns	2.14	0.01	-	-	-	NA
Metadata_Qualified	100	10	1,024.2 ns	2.99 ns	2.80 ns	2.61	0.01	0.0076	-	40 B	NA
Metadata_Multiple	100	10	1,253.2 ns	4.38 ns	4.09 ns	3.19	0.01	-	-	-	NA
Mixed_PropertyAndItem	100	10	9,797.1 ns	23.63 ns	22.11 ns	24.94	0.07	0.1678	-	954 B	NA
Mixed_PropertyAndMetadata	100	10	2,299.7 ns	4.41 ns	3.91 ns	5.86	0.02	-	-	-	NA
Mixed_All	100	10	12,151.7 ns	22.81 ns	20.22 ns	30.94	0.07	0.2136	-	1170 B	NA
NoExpansion	100	10	392.8 ns	0.81 ns	0.72 ns	1.00	0.00	-	-	-	NA
PropertyAndUnescape_Multiple	100	10	1,753.9 ns	4.22 ns	3.95 ns	4.46	0.01	-	-	-	NA
ItemListAndUnescape_WithTransform	100	10	12,762.8 ns	23.90 ns	21.19 ns	32.49	0.09	0.1831	-	962 B	NA
MetadataAndUnescape_Multiple	100	10	1,262.9 ns	2.16 ns	2.02 ns	3.22	0.01	-	-	-	NA
MixedAndUnescape_All	100	10	12,250.3 ns	19.17 ns	16.01 ns	31.19	0.08	0.2136	-	1170 B	NA

Property_Single	100	100	441.5 ns	3.14 ns	2.78 ns	1.22	0.01	-	-	-	NA
Property_Multiple	100	100	1,723.2 ns	6.39 ns	5.98 ns	4.77	0.02	-	-	-	NA
Property_Nested	100	100	1,235.0 ns	2.10 ns	1.86 ns	3.42	0.02	-	-	-	NA
Property_Concatenation	100	100	2,079.8 ns	3.31 ns	2.93 ns	5.76	0.03	0.0038	-	28 B	NA
ItemList_Simple	100	100	19,358.1 ns	18.49 ns	16.39 ns	53.63	0.22	0.1526	-	874 B	NA
ItemList_WithTransform	100	100	109,961.7 ns	189.90 ns	158.57 ns	304.62	1.59	1.4648	-	7816 B	NA
ItemList_WithSeparator	100	100	10,761.7 ns	27.46 ns	24.34 ns	29.82	0.11	1.7395	0.0305	9162 B	NA
Metadata_Unqualified	100	100	825.2 ns	1.30 ns	1.15 ns	2.29	0.01	-	-	-	NA
Metadata_Qualified	100	100	1,035.7 ns	2.98 ns	2.79 ns	2.87	0.02	0.0076	-	40 B	NA
Metadata_Multiple	100	100	1,271.4 ns	3.37 ns	3.15 ns	3.52	0.02	-	-	-	NA
Mixed_PropertyAndItem	100	100	72,998.2 ns	198.24 ns	185.43 ns	202.24	1.08	1.4648	-	7806 B	NA
Mixed_PropertyAndMetadata	100	100	2,250.0 ns	5.41 ns	5.06 ns	6.23	0.03	-	-	-	NA
Mixed_All	100	100	75,466.4 ns	111.68 ns	104.47 ns	209.08	0.96	1.4648	-	8022 B	NA
NoExpansion	100	100	361.0 ns	1.66 ns	1.56 ns	1.00	0.00	-	-	-	NA
PropertyAndUnescape_Multiple	100	100	1,780.2 ns	6.08 ns	5.69 ns	4.93	0.03	-	-	-	NA
ItemListAndUnescape_WithTransform	100	100	109,854.9 ns	162.79 ns	152.28 ns	304.35	1.32	1.4648	-	7816 B	NA
MetadataAndUnescape_Multiple	100	100	1,256.2 ns	2.39 ns	2.23 ns	3.48	0.02	-	-	-	NA
MixedAndUnescape_All	100	100	74,960.3 ns	121.18 ns	107.42 ns	207.68	0.87	1.4648	-	8022 B	NA

Highlights

2–3× faster metadata expansion across both runtimes
Zero allocations for unqualified and multiple-metadata scenarios (previously 624–1,248 B on .NET 10, 369–741 B on .NET Framework)
Transform-based expansion also benefits slightly (~350 B savings on .NET 10, ~224 B on .NET Framework) due to shared infrastructure improvements
No regressions in any other expansion scenario (property, item list, separator)

Copilot

Pull request overview

This PR refactors MSBuild’s evaluation-time metadata expansion to remove regex usage and replace it with a manual, allocation-conscious scanner, aiming to reduce per-expansion overhead in the Expander hot path. It also updates related transform parsing and adds new microbenchmarks to measure the impact.

Changes:

Replaced regex-driven %(...) metadata expansion with a manual scanner in Expander.MetadataExpander.
Centralized metadata token parsing via ExpressionShredder.TryParseMetadataExpression and updated item transform metadata matching to avoid regex.
Added ExpanderBenchmark to quantify perf/alloc changes; removed now-unused regex helper files and project includes.

Reviewed changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated 8 comments.

Show a summary per file

File	Description
src/MSBuild.Benchmarks/ExpanderBenchmark.cs	Adds new benchmarks covering property/item/metadata/mixed expansion scenarios.
src/Build/Microsoft.Build.csproj	Removes compile includes for deleted regex-based expander helpers.
src/Build/Evaluation/ExpressionShredder.cs	Adds a metadata-expression parser helper and switches to `Strings.WeakIntern` usage.
src/Build/Evaluation/Expander.RegularExpressions.cs	Removes regex infrastructure previously used by metadata expansion.
src/Build/Evaluation/Expander.MetadataMatchEvaluator.cs	Removes regex match-evaluator infrastructure used for metadata replacement.
src/Build/Evaluation/Expander.MetadataExpander.cs	Rewrites metadata expansion to a manual scanner and gap-handling logic around item vectors.
src/Build/Evaluation/Expander.ItemExpander.Transforms.OneOrMultipleMetadataMatches.cs	Updates match container to support manual-scan match info.
src/Build/Evaluation/Expander.ItemExpander.Transforms.MetadataMatchType.cs	Minor formatting/structure updates for match-kind enum.
src/Build/Evaluation/Expander.ItemExpander.Transforms.MetadataMatch.cs	Replaces regex `Match`-based storage with index/length storage.
src/Build/Evaluation/Expander.ItemExpander.Transforms.cs	Replaces regex matching for quoted expression metadata with manual scanning + `TryParseMetadataExpression`.

jankratochvilcz

Expert MSBuild review (automated)

High-quality, faithful refactor. The hand-written ref struct scanner reproduces the previous regex behavior across the edge cases I checked (qualified vs. unqualified metadata, internal/surrounding whitespace, nested %(a%(b)), malformed %()/%(, built-in-vs-custom gating, truncation, and self-reference logging). I verified parity empirically: the project builds with 0 warnings, and Expander_Tests + ExpressionShredder_Tests produce the same pre-existing macOS-platform failures on this branch as on origin/main — i.e. no regressions introduced.

String-comparison correctness is preserved (MSBuildNameIgnoreCaseComparer for the metadata dictionary, IsItemSpecModifier case-insensitive, ordinal for the self-reference item-type check and the %(/@( pre-scans). Name-character validation via XmlUtilities.IsValid*ElementNameCharacter is equivalent to the old regex's [A-Za-z_][A-Za-z_0-9\-]*.

The one substantive item worth addressing before merge is the avoidable double-parse of the item-vector expressions on the mixed @(…%( path (mildly counter to the PR's perf goal). The rest are nits. Nice addition of ExpanderBenchmark to back the perf claims. No blocking issues.

…sion Introduces ExpanderBenchmark to MSBuild.Benchmarks covering: - Property expansion (single, multiple, nested, concatenation) - Item list expansion (simple, transform, custom separator) - Metadata expansion (unqualified, qualified, multiple) - Mixed expressions (property+item, property+metadata, all) - ExpandIntoStringAndUnescape variants for unescape overhead - NoExpansion baseline Parameterized on PropertyCount and ItemCount to measure scaling.

Eliminate all regex usage from metadata expansion by replacing it with a manual span-based scanner that delegates to a shared parsing method. - Extract TryParseMetadataExpression on ExpressionShredder as the single shared metadata parsing implementation, using the existing Sink pattern and Strings.WeakIntern to avoid allocations. Refactor ExpressionShredder's own inline metadata parsing to call the new method. - Refactor MetadataExpander from a static class to a readonly ref struct, capturing expansion context in fields and converting static methods to instance methods. Also, annotate for nullability. - Inline MetadataMatchEvaluator logic into MetadataExpander and delete the type - Rewrite Transforms.GetQuotedExpressionMatches to use manual scanning instead of ItemMetadataRegex - Delete Expander.RegularExpressions.cs (entirely dead code) and Expander.MetadataMatchEvaluator.cs - Replace s_invariantCompareInfo.IndexOf with string.Contains for simple ASCII substring checks

Declare return type of MetadataExpander.ExpandMetadataLeaveEscaped as `string` rather than `string?`.

ScanAndExpandMetadataInGaps re-ran ExpressionShredder.GetReferencedItemExpressions from scratch even though Expand had already shredded the expression to test the single-item-vector fast path. For any expression containing "@(" that isn't a lone full vector (e.g. "prefix@(Compile)" or "@(A);@(B)"), that parsed the first capture and interned its "@(...)" substring twice, throwing away the first pass. Thread the already-advanced enumerator into ScanAndExpandMetadataInGaps so the shred happens exactly once, restoring the single-pass behavior of the original ExpandMetadataLeaveEscaped. The enumerator is passed by ref and consumed with a do/while since it is positioned at the first capture on entry. The no-capture case (string contains "@(" but no well-formed item vector, e.g. "%(Culture)@(") is handled explicitly by scanning the whole string for metadata, so malformed-but-benign input keeps working rather than throwing.

The PR that replaced the metadata-expansion regex with a hand-written character scanner added only a benchmark, leaving the scanner's branches without explicit coverage. Add focused Theories over Expander.MetadataExpander that pin the exact expanded result so future edits can't silently regress them: - ExpandMetadata_ScannerEdgeCases: surrounding/internal whitespace, malformed references (%(, %(), %( ), %(.x)), nested references (%(Culture%(Foo))), qualified vs. unqualified names, and missing metadata. - ExpandMetadata_ItemVectorGapsAndSeparators: metadata before/after/between item vectors, the lone-vector fast path, metadata embedded in a separator, and a stray "@(" that doesn't form a valid item vector. - ExpandMetadata_BuiltInVsCustomGating: built-in vs. custom expansion is gated on the matching ExpanderOptions flag (declared internal since ExpanderOptions is internal; xUnit discovers non-public test methods).

Replacing the metadata-expansion regex with a hand-written scanner dropped the "keep in sync with ProjectWriter" note that the deleted Expander.RegularExpressions.cs carried. The scanner validates item type and metadata names via ExpressionShredder.SinkValidName (XmlUtilities.IsValidInitial/SubsequentElementNameCharacter), which is exactly [A-Za-z_][A-Za-z_0-9\-]* — equivalent to ProjectWriter.itemTypeOrMetadataNameSpecification today. Restore the coupling note in three places so the two grammars can't silently diverge: - ExpressionShredder.SinkValidName (the shared validator) - Expander.MetadataExpander.ScanAndExpandMetadata remarks - ProjectWriter.itemTypeOrMetadataNameSpecification (back-reference) Documentation only; no behavior change.

The end parameter was only respected by SinkValidName; SinkWhitespace and the single-char Sink bounded on expression.Length, so the metadata parser could read past end. This was benign for current callers (the gap scan always has '@' at end, which fails the name/'.'/')' checks before any over-read), but it was a latent footgun now that this is a shared, named internal helper with an explicit end. Add end-aware overloads Sink(expression, ref i, end, c) and SinkWhitespace(expression, ref i, end), and route TryParseMetadataExpression through them so no character at or beyond end is read. The existing Length-bounded overloads now delegate to the end-aware versions, removing duplicated bounds logic. Also tidy the surrounding XML doc comments. No behavior change for existing callers.

The de-regexed transform scanner (GetQuotedExpressionMatches) had no test covering its qualified-metadata error path. Add a Theory asserting that a metadata reference qualified with an item name inside a transform throws InvalidProjectFileException, and that the message reports both the offending reference and the suggested unqualified form. Cover the internal-whitespace variant (%( i . Meta0 )) so the scanner's whitespace handling on this path is pinned too.

Replace the character-by-character for-loop in ScanAndExpandMetadata with a while loop driven by string.IndexOf("%(", ...), so the search for the next metadata reference benefits from vectorized scanning instead of inspecting each character in managed code. Behavior is unchanged: a "%(" at endIndex - 1 still can't form a reference, failed parses resume past the "%(", and successful expansions resume after the reference.

AlesProkop · 2026-06-23T12:35:46Z

@jankratochvilcz triage: Do you approve?

AR-May

LGTM. I think it is worth to get a bit more test coverage, so I triggered experimental VS insertion for this PR.

Upd: No failing tests, insertion shows a good improvement of BytesAllocated metrics. Ready to merge.

Copilot AI review requested due to automatic review settings June 19, 2026 21:30

Copilot started reviewing on behalf of DustinCampbell June 19, 2026 21:30 View session

github-actions Bot mentioned this pull request Jun 19, 2026

[aw] Expert Code Review (on open) failed #14118

Closed

Copilot AI reviewed Jun 19, 2026

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jankratochvilcz reviewed Jun 22, 2026

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DustinCampbell requested a review from a team as a code owner June 22, 2026 17:16

DustinCampbell added 12 commits June 22, 2026 10:17

Remove unused using directive

155ef33

Don't dispose ProjectCollection in ExpanderBenchmark early

6ae082f

Tighten null annotated on ExpandMetadataLeaveEscaped return type

4361cf8

Declare return type of MetadataExpander.ExpandMetadataLeaveEscaped as `string` rather than `string?`.

Scan for "%(" and "@(" with StringComparson.OrdinalCompare

243ad29

Use platform-neutral project path in ExpanderBenchmark

8d43405

DustinCampbell force-pushed the metadata-expansion-perf branch from 820a99f to 140da40 Compare June 22, 2026 17:17

rainersigwald approved these changes Jun 22, 2026

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Comment thread src/Build/Evaluation/Expander.MetadataExpander.cs Outdated

AR-May approved these changes Jun 23, 2026

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AR-May merged commit 608629d into dotnet:main Jun 24, 2026
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DustinCampbell deleted the metadata-expansion-perf branch June 24, 2026 16:20

This was referenced Jun 25, 2026

[release/10.0.4xx] Source code updates from dotnet/msbuild dotnet/dotnet#7370

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[main] Source code updates from dotnet/msbuild dotnet/dotnet#7372

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Replace regex-based metadata expansion with manual scanning - #14116

Replace regex-based metadata expansion with manual scanning#14116
AR-May merged 13 commits into
dotnet:mainfrom
DustinCampbell:metadata-expansion-perf

DustinCampbell commented Jun 19, 2026

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DustinCampbell commented Jun 19, 2026

Summary

Changes

Benchmark Results

.NET 10.0 (PropertyCount=10, ItemCount=10)

.NET Framework 4.7.2 (PropertyCount=10, ItemCount=10)

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Pull request overview

Reviewed changes

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Expert MSBuild review (automated)

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AlesProkop commented Jun 23, 2026

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